Distributor, spark plug cables and HV coil

[Marco]

Hi guys
I please ask a suggestion, engine is running great.
I saw the HV coil super dirty, indeed many parts are dirty and black covered in a 40years old cars, so I bought from Autodoc a new coil, it’s Bosch part number 0221502431, sold as compatible with 2.3-16 all types: ECE, RUF, CAT; can you comment if this component is fine?

So I’m wondering to replace distributor, distributor cap and spark plug cables.

I heard a lot about the need to use correct cables ( they have resistance inside ?)so I’m wondering if I can buy Beru o Bosch or is better to have the correct component paying more in Mercedes?
Are there differences between ECE and RUF?

I see three types of distributor (the rotating part), why?

IMG_5764.jpeg

The spark plug I will replace in car after I discover if my engine is an ECE or RUF…

Thanks for any tips

Marco

[shaq]

Hi Marco,

At time of production, all 16v parts were of better quality then you can buy today. It is a proven fact.

It is General truth for almost all the cars: all parts you buy later never match quality of Factory assembly (due to many reasons...)

Your engine is ECE otherwise you would measure 170, 175 horse power on Dyno not 183...

Old 16v engines they go down with max power as they get old, they never go up from factory values, ONLY do if you do rebuild and some serious tuning. That means, more RPM, much higher compression and flow and timing improvements!!! Maybe 1000 Euro for each HP gained, I am talking about real HP not K&N Filter imagination or Remus exhaust

Same is fact for M102 8v engines, but 8v engines hold power for much longer maybe 200t km because of self-adjusting valves and lower RPM used. Our 16v engines, especially KAT versions need FULL REBUILD, including larger bore, new pistons every 100t km to stay with max declared power. Yes they can run much longer but power goes down significantly sometimes even 30 HP down in my experience...

Coil of 16v was more powerful than other coils of Mercedes of the time. And you change it to some universal Part No. because it is dirty???

You should change it ONLY if you have measured it and it is out of spec (0.001% probability) because it will rather stop igniting then go out of spec.

You buy shit quality from autodoc

Dont do it man because Autodoc and similar platforms based on TecDoc database engine for specific cars like 16v they give universal part numbers that should never be installed in our 16v cars. If you need specific part like coil go to Mercedes and buy part there because only they have full reference and specifications.

Bad coil can destroy EZL (ignition computer) so badly that you would need to buy new one, and it is VERY VERY HARD to get, if not impossible because it is resistance and impedance matched to coil !!!

About distributors yes there is with resistor inside (I think all have it inside) and there is wider or narrower version (more security for transmitting the spark inside distributor) for early ignition during acceleration etc.

About cables I prefer Beru over Bosch, for normal 16v you will see little difference, but for perfomance engine I had better results with Beru than Bosch, in test I conducted Beru cables with copper core outperformed Bosch with carbon core so I never buy Bosch again because with Bosch I had some missed ignitions and I didn^t like that .

I understand you love your 16v and want to do best for it. but DON´T Repair if it is Not Broken !

Regards,
Nikola.

[Marco]

Dear Nikola
Thanks so much for your reply and efforts, ok very clear I’ll no replace anything if it is not broken (but for rubber parts like hoses may be is needed…).
I bought this HV coil and I’ll put in the drawer very clear, I promise I follow your recommendations.

Can you confirm is stupid also to replace the spark plug cable, distributor and cap distributor ? All works I confirm but I’ve always heard spark plug cable deteriorates because of hight voltages passages…

I replied to your private message many time but the message remain in outbox… so I post here.
I did the compression test, despite mechanic said engine is super fine he doesn’t know it should give 13-14bar see picture

5bcdfd0a-ddcf-45e1-8b79-941c1a22a906.jpeg

I asked a picture of the spark plug to see if is an ECE or RUF type …unfortunately the picture is useless…

So 11.3bar but this is the power curve 183HP and even more torque…
Can be an ECE with 11.3bar only?
2bar lost with only few HP less?

You told me an endoscopy cannot help because is difficult to see the piston .

I much value all your suggestions
Have a nice weekend you all
Marco

[shaq]

Hi Marco,

I prefer to answer here as it is not just you and me, this post maybe help somebody else maybe in 15 years. So is always better to write in Forum than in PM.

Cable don't get damaged from heat or time passing by. Only if some hungry rodent eat it from outside.

Of course all rubber parts wear out from heat and time - such as hoses etc. but for cables they die if spark plug gap goes out of spec for too long

Because voltage needed to jump between spark plug electrodes is determined like 9.000 Volts when gap is correct (0,8mm) and combustion is correct. Cables can handle when new much more like 14.000 Volts and used like 12.000 Volts. That is called "safety margin"

But if spark plug is neglected and not controlled for VERY long time and gap becomes too big (like 1,0mm) and yes, gaps do increase as mileage is driven it is called - a normal wear - than voltage needed to create spark can rise above that for example as high as 16.000 Volts (because voltage-gap is related not directly but with power of 2 so for gap 2 times increase voltage will increase 4 times if I remember correctly the formula) and spark will not be able to jump anymore where the spark plug is where it should happen,

but in some other place with lower electrical (voltage) resistance like somewhere in the middle of the cables to outside metal (valve cover) so cables will die, or can happen that coil or EZL computer get damaged because of high voltage will burn insulation inside coil (cause short circuit and death of coil) or power transistor inside of EZL will die. Of course when spark dont happen in cylinder there will be rattling noise and damage to Catalyst for KAT cars.

Voltage also increases DRAMATICALLY if fuel to air ratio is LEAN due to bad injector, turbo or LPG powered vehicle so even there it could be 16.000 volts even with 0,9 gap

SO is VERY important to control your spark plugs at least every 20.000km change them if necessary they are not expensive or just clean them (the best is soda blasting that is what I use in my garage) and set up correct gap.

ALSO very IMPORTANT is to check how spark plugs looks. Allowed is light grey or light brown electrode top. If filled with carbon deposits inside ceramics it can indicate bad injector or high oil conumption and engine needs to be repaired as soon as possible or injector or KE Jetronic head replaced!

I am also against multi-electrode spark plugs as they are not designed for our standard ignition coils and how are you sure you can adjust gap in them because for 4 electrodes there is 2 pair of different gaps. Motorsport coils is something else there everything is different from ECU through coils and plugs...

For standard 16v I use OEM spark plugs BERU single electrode, correct thermal value, for tuned car one value colder if needed - which I buy directly from Mercedes. Again I myself dont use Bosch as Bosch is often counterfeit in free market and spark plugs for 16v I think are not available anymore you get some universal replacement

Check gap also on new ones because lot of w201 parts get discontinued, like we discussed above, and new part number maybe fits BUT gap is not 0.8mm like needed but 1.0mm from factory!!!

Take spark plugs always on cold engine not to damage the threads, dont overtighten them not to damage threads, and dont remove them too often not to damage threads. Is all very important because if you damage thread it will be very hard to repair (thread repair inserts are very bad thing because made out of steel and never able to cool spark plug like aluminum so it melts ceramic every 1000km and one start to cry as there is no solution except new cylinder head...) so once checked live them alone for next 20.000km

About compression yes it is low for ECE it is more in RüF/KAT Range, did you measure hot or cold? Is measuring instrument accurate? They are more often off than correct in my experience. They should be calibrated once in a year... Also are you sure you have 183HP? I mean they whom measured your car, they can not measure engine directly, they measure at rear wheel and than multiply result by corrective factor taking in account gear box, temperature, DIN Standard. I assume they did something wrong. Also 16v should be measured in fifth gear not in fourth like most cars (due to 1:1 gear ratio). How much HP they measured at wheels? 145, 150?

Now I look at your Power diagram. To me it is VERY strange, you have constant 180HP from 5250 to 7000 Rpm which is impossible for 16v (only possible to look like this for Honda VTEC engines or varialbe turbo which you don´t have if I am aware), I would say that measuring equipment is defective. Also EZL should cut ignition off at 7100 for ECE engine, but they manged to rev to 7250 it is also for me not possible that dead engine roll for next 150 RPMs more

Correct it should look something like this, max Power between 5500 and 6000 then falling down:

Mendoza.JPG

Regards,
Nikola.

[Marco]

Good morning Nikola
Thanks for detailed explanation on spark plug cable and spark plug. Ok clear the most important thing is the spark plug gap.
Unfortunately from the picture I can see only it’s Beru spark plug, I know it has less then 10000km and I can read the 0,8 at the base of the threaded metal, but yes it’s to be checked to be sure.
As original Beru 14K-5DU (for ECE like the metal plate I have in engine bay) and 14K-6DU (more for RUF) are not available are you please able to suggest a Beru part number I should look for? Or do we have to identify before if is an ECE or RUF?
Even if I buy in Mercedes I’d like to be sure on what they give me because from EPC most original part are not available and they provide some “equivalence” that are not always matching but just the less worst they can have now… you know? Refrigerant they sell now only red which is as you know for new aluminium block engines…if you go in Mercedes they can fill up this into your blue green …. And if they are correct at least they ask …

Form the picture are you able to comment the spark plug electrode? To me look good.

Is it a risk if instead to replace the HV coil I keep the original part and remove for a good cleaning from years of dust. I’d use brake cleaner or electrical spray contact and a soft brush, I can’t see much risk on this but please comment if I risk to do a stupid thing.

I’ll remove and check the distributor and distributor rotor contacts if fine but ok not changing if not ruined.

About the engine compression test, unfortunately I was not present that moment but mechanic told me the manometer is new and about engine temperature he did a small road trip to check suspensions after replace of rear bushing. So engine was not in full operating temperature but not cold for sure.


I see your point on the power measurement but unfortunately I can only rely on what they reassured but of course we know that the vine is always good for the seller…I can pass in the future to ask if they stored the data with the power at wheel …it will take time…
Yes I can also confirm engine is stock it has 80000km from the replacement in Mercedes, I’ve the invoice dated 1992, here the doubt if they put back the original ECE or a low compression RUF but for sure all the engine management is still ECE.
From all I translated here I understood that is quite difficult to understand 100% after engine number 5000 if ECE or RUF for engines used for replacement but these is the numbers:

102983 10 006519 original
102983 10 017749 new

Sorry if I ask again do you confirm an endoscopy is not helping?

Once more I appreciate all the time you spend here and sorry to annoy on half stupid questions:)

Best
Marco

[shaq]

Hi Marco,

ECE Kolben.png

ECE piston is little taller from side than RüF/KAT and from above with Endoscope you can´t see it in my opinion.

I can distinguish them when I see them removed from the engine by looking at distance from top to first compression ring. For ECE is larger distance to be seen.

About engine No. there is Post from me about exact serial numbers, what I remember for ECE there was initial production run from 0-some 5-6.000 and than second production run with much higher numbers for spare engines.

Also back in 1992 they had enough new engines, and it is Mercedes official politics only to install same engine type.

Later in 2000s ECE engines were sold out, last available for purchase were USA and RüF/KAT with lower compression and lower max power.

So in my opinion if your engine was officialy exchanged by a Mercedes dealer you got again ECE engine, and if it was done by some private (small) garage than anything is possible. They did what was cheaper for them...

All 2.3 16 engine blocks are the same, only pistons are different (conrods too for early ECE and matching crankshaft).

So it is easily possible to make ECE form RüF/KAT and vice versa by pistons change.

Today on rebuilds some members install pistons on 2.3 16 with higher comperssion than factory ECE to gain even more power as for today´s traffic 185 horses is not much like it was 1984... What was 2.3 16 back then in traffic is today C63 AMG in my opinion. And 177 or 185 horses today is not much, my personal opinion - fun starts from 300 horses and up...

Bye,
Nikola.

[Marco]

IMG_5794.jpeg

Dear Nikola
Useful info from your side, yes I guess that talking 170 or 185 is like nothing comparing with today’s AMG and the car you have in you garage but you know every single pony is at least nice to know you are entitled to have or not, and we are here also on these details.
I have the invoice from PO with Mercedes invoice for a lot of money where in 1992 they exchanged the engine with gearbox I can also add as curiosity that they did not update in the system so after more than 20 years I opened a procedure and upon their inspection of the engine number they have update the engine in EPC system with my original VIN.

About piston as I know the easiest way to distinguish is that CAT/RUF has concave surface where ECE is just flat, see this picture for RUF/CAT:

[Marco]

For the spark plug I studied all the weekend all the site from Beru Bosch champion and also Brisk and denso to find the equivalence of the original not resistive spark plugs unfortunately unless going to eBay that I don’t know the origin they are no more available…or I’m not able to find. I’ll ask in Mercedes what they can offer …

But please read below my idea in two weeks when I’ll be back with the car:

Ill take these measurements:

check n.1 spark plug installed to see the code and as scruple check for 0 Ohm resistance

Measure n.1 spark plug cable, should be 1000 Ohm (resistance in the spark plug connector)

Measure each of 4 distributor cap resistances should be 1000 Ohm

Measure the distributor (the turning finger) resistance should be 1000 Ohm

Above resistance info I took from the service manual supplement engine 102.983 for USA market …I think CAT engines are same for these point of view as ECE, except the spark plug where originally they recommended Bosh H6DC or Beru 14k-6DU or Champion s7yc which is hotter than my original ECE bosh H5DC or beru 14k-5DU or champion s6yc.

I’ll measure HV coil resistance to compare with the new unit Bosh (part number matching OEM part).

If you think this make senses and can be useful for anyone in the future I can do and post here.


Thanks again wish you a nice new week ahead
Best
Marco

[shaq]

Hey Marco,

About piston as I know the easiest way to distinguish is that CAT/RUF has concave surface where ECE is just flat, see this picture for RUF/CAT:

No that is WRONG, every 16v piston in repair size 1 or 2 (when block is bored to bigger bore 96 or 96.50mm respectively) has concave top to prevent higher compression after install.

So even ECE in repair size will have dish on top it is normal...

Every 2.3 16 and 2.5 16 (except EVOs) had flat pistons from factory (95.50 factory cylinder bore). It looks like this from above:

standard piston.jpg

So believe me, I know what i am talking about, only way to say for sure is to take a look at piston from side, and better measure not look

Only EVO 1 and EVO2 have standard pistons with concave top again to have compression not too big for everyday car because their engine geometry (bore/stroke) is different...

And Evo blocks dont have repair size, they are not meant to be bored even if some people do this especially Evo2 where wall to water channel is VERY thin

So picture of yours is either Evo pistons or repair size pistons (I assume repair size as Evo parts dont circle the internet), and if your engine is new from Mercedes you must have flat pistons.

To be 100% sure about your pistons, whether they are ECE or KAT/RuF you must take them out of the engine or use X-rays, with endoscope you can just see "flat earth" and very black

Please don't do that without a important reason (just to look), it would be very wrong decision and compression you shoved above tells me it is not ECE pistons or valves are dead they dont close properly

If valve dont close properly you would need to rebuild the head, and to say if they close or not you can do vacuum test from outside with only manifolds removed.

If this is same picture from Internet than please check the detils, it is piston for bored block (repair size 1):

rep size.png

Now back to the ignition system:

I know for sure that spark plug connectors have 1000 ohm and it is mostly built in for cancelling radio noise caused by ignition system.

When I drive 16v I prefer to turn off the radio, I rather listen to engine so I could do with or without 1000 ohm

That is also engraved onto them. Now cables have almost no resistance and finger has (i believe you are correct 1000 ohm) for the same reason.

About distributor cap I don't know (I doubt) it has 1000 Ohms as I never measured.

For all this 1k resistor there is a simple reason - resistance is put close to point where it sparks (also it sparks in distributor - of course as it is NOT contactless so distributor finger must have 1000 Ohm) to suppress radio noise in all empty spaces caused by that same spark "travelling" from coil to spark plug!

Now about your new ignition coil to measure resistance means almost nothing, to measure inductance means how much electrical energy (spark energy) can it store between two sparks because it is essential for good quality spark.

As 16v can get leaner in some rev points and it revs higher they put stronger coil to make sure spark happens every time and engine survives (avoids knocking) and everything is OK.

16v engine ventilates cylinders faster and better than others so lot of things can happen quickly especially when it resonates.

Like I wrote above it is much harder to create spark in dry (fuel lean) environment than in enviroment wet from gasoline/air mixture. Voltage rises suddelny for 1000s of Volts...

And it is where 16v coil differs from 8v/12v coils. How can you measure accumulated energy your old versus new coil, do you have a Lab at home?

You know I am kind of scientists (I have master in electrical engineering) and I measure, I dont take things for granted

About spark plugs, I use old stock from Mercedes, it is Beru and it is made in France. They are each packed in a Mercedes box. And if you go shopping I think if "made in France" is engraved in them, and they are Beru they are not counterfeit. Or try to find somewhere (marketplace, announce...) old stock even Bosch Super from 80s, they had copper electrodes it is easy to tell it is a real thing as today copper is expensive and surely not used by cheaters...

Regards,
Nikola.

[Marco]

Hi Nikola,

admiring your knowledge these considerations on the pistons are also very clear, so only engine from factory had flat piston head, and if I check mine it is still not a solution because also RUF/CAT would be the same i.e. flat from factory.

This would be not the solution but as a matter of curiosity a new engine from Mercedes in my invoice is mentioned part A1020106444 80 and the order job is called engine replacement with a "rotation engine" I take it as an engine rebuilt by Mercedes am I wrong saying in this case it should be with piston repair size 1 or 2 so concave top not flat? But yes we would be at the same point.

I will not ask for the endoscopy you had been very clear.

Ok my compression is not good (at least for the single cylinder tested) but I suppose that if I had valves dead I should have some important problem, knocking at least, but the car pull strong and speedometer passes 240 quite easily, you saw the power bank records, even if want to say it shows excessive good numbers the cuve is contineous and without a single discontinuity, can be still the case of valves dead? So this could be a RUF engine in good health with ECE controls? I’ve a very minor leakage of oil from engine block head gasket just over the chain tensioner plug and on the opposite side a drop of refrigerant between cylinder 2 and 3 below the air intake manifold, mechanics also in Mercedes says this is not even close to think to dismount to replace the gasket and so far I never add neither oil nor refrigerant.

Worth to mention that I asked Mercedes the spark plug they have available and they propose me the only that remain from EPC which is A0031590803 H 5 DCO BOSCH so thermal grade 5 that, correct if I'm wrong, it was only for ECE, neither EVO had so cold grade.
But still I'm not 100% convinced they have real control and understanding of their system, even if the engine number had been updated with the VIN.

[Marco]

about the ignition system

I also never listen radio and I don't care about radio interference but my thought was to keep the factory chain of resistance/not resistance components, may be I'm wrong but as you recommended to not mess with ignition coil I searched and found the data I posted from the US service manual supplement for engine 102.983, they had CAT version imported officially but as I said and from some cross check even if I can't put hand on fire, spark plug connectors, wires, distributor and HV coil are the same for all the ECE/RUF/CAT.
They specifically mention interference suppression resistors: on distributor cap per connection 1KOhm and distribution rotor 1KOhm.
Again, may be I'm wrong and this is only for the el interference but keeping original I suppose this also works correctly with the HV coils for the purpose of the ignition, not having resistance spark plug (usually they are 5-10 kOhm as I found, our are zero).

I meant to measure HV coil resistance to see and compare with the new Bosch that I ordered (whose PN match with Mercedes OEN) and see if they are matching for this, but OK I see this is very stupid and useless because it's the inductance that counts where I cannot measure H (Henry). It started just becuase I saw this part so dirt...at the end I'll just remove to clean and dry with brake fluid spray.

Are you so kind to tell me the Beru spark plug you have from stock? But I'm not sure you install in a 2.3 ECE or RUF...
am sorry but I'd appreciate also this if you have any comment on the BOSCH H5 DCO I just ordered in Mercedes that they offered from EPC:
- in the remote case I don't have the ECE, is there any associated risk with grade 5? just difficulty to crank with cold engine or something worst? I still think that in the doubt is always better colder that hottest spark plug
- I could not find any description to see where H5DCO differs from original H5DC ...the O probably means "differences from basic design"...but what does this means probably only the scientists in Bosch laboratory know

thanks for your time!
Marco

[shaq]

Hi Marco,

Here is pictures of my old spark plugs I still have in my garage.

423568254_397660056118620_2349078258702300096_n.jpg

423221561_362369223257481_9105707903443625035_n.jpg

423147409_1525719228219704_3670663444379125691_n.jpg

423599941_1430936107546884_6427478922130125078_n.jpg

423036735_268845846092069_3225242768376154721_n.jpg

423036329_2340985129566749_4850067572130770140_n.jpg

I see that I have Beru with thermal value 6 (2.5 16) and also 8 (for some experiments)

From Bosch Super H7 DCO, copper plating is still visible.

They are all OK but I liked Beru the most and I remember I didn't like NGK but don't ask me why (was long ago)

About defect valves, yes it happens at 16vs and they can leak compression with those valves. Especially Exhaust receive damage. See that picture how contact surface is with holes in it. That in the engine is the bad thing and needs change.

423686537_883364690244974_4074387762771967765_n.jpg

[shaq]

Hi Marco,

Here I took some pictures from my garage for you, because you showed interest in details - it is 2.5 16 Piston, ECE Piston, EVO2 Piston and EVO2 DTM Racing Piston.

If you ever overhaul engine I recommend piston that is long like 2.5 16 but has roof like DTM (coswort house-roof type piston) custom made. Than car goes much, much better

16v Kolben.jpg

4.jpg

2.3 16 Kat is similar to 2.5 16 but not same location of shaft - all because of different Crankshaft and different stroke

Short pistons rev the best but engine last only 1000km

ece vs 2.5 16.jpg

ece vs 2.5 16 unten.jpg

2.5 16 pistons have tendency to eat the cylinder bore because they are short and they "dance" more in OT

2.3 16 are quite long and therefore gentle to the cylinder (don't destroy it fast like 2.5 do) they "dance" much less in OT but driver must care not to overrun engine (past 7100 RPM) as they are heavy.

DTM Pistons "dance" like Michael Jackson in OT

Reason is simple - look how Piston sleeve is short...

Heavy pistons have little reserves on overrun RPMs, 2.5 are shorter can rev much more but it has its price like said above.

DTM vs 2.5 16.jpg

DTM vs 2.5 16 II.jpg

Notice how DTM Piston has also super thin Shaft inside.

Notice production date of ECE (07 84) and 2.5 16 Piston (09 89)

ece datum.jpg

2.5 16 datum.jpg

They are all MAHLE Stuttgart only DTM I think is WIESECO.

[Marco]

Thanks Nikola for posting so many pictures !
I mentioned that I hope in my case the Bosch H5 DCO ordered in Mercedes are fine for my engine …because thermal grade 5 I saw is suggested only for ECE so I hope they are 100% sure mine is ECE …
Anyone tried a grade 5 in a RUF engine? …just in case

Useful to see the valve with the small holes on the surface contact, when does technically happen ? When engine clearance is wrong ? Or it has nothing to do and is more related to valve springs?
Am I supposed to notice some wrong behaviour of the engine ? if I had defect valves? because as I mentioned I can’t see anything wrong but I’m not such expert, so I’m asking if I risk also a catastrophic damage.

For the pictures of the pistons I’ve still to look them carefully, they are interesting…may be if I’ll need you can sell or address me where to buy pistons (for street use of course).

Wish you a nice evening
Marco

[shaq]

Marco,

Useful to see the valve with the small holes on the surface contact, when does technically happen ? When engine clearance is wrong ? Or it has nothing to do and is more related to valve springs?
Am I supposed to notice some wrong behaviour of the engine ? if I had defect valves? because as I mentioned I can’t see anything wrong but I’m not such expert, so I’m asking if I risk also a catastrophic damage.

Catastrophic damage at ECE can only be breaking of timing chain. Check your service book when last time it was changed. Best to change it every 70.000 km

About bad valves. You will just see that you have less power than good engine. But with whom can you compare cars?

Pockets on pistons are more safety measure. no valves in normal operation never go inside those pockets.

And if you ever overhaul that engine, no I dont sell parts. But:

There is small private company near Stuttgart they produce the best custom pistons price was 1k Euro now with inflation is about 1.5k for set of four as I am informed

They are "Wahl Spezialkolben" GmbH,

They use the best castings (MAHLE) and machine them to customer specification .

Price is same or similar I think whether Pistons are flat or they add "spices" to it.

Good thing is they add all the special details for you, even recommend this or that because have lots of experience in all applications you can dream of even F1 secrets...

Because 16v pistons are hard or nowhere to buy so for many owners this is the solution. Even in Mercedes since long ago price for set is around 1k euro.

There are some 16v pistons on ebay but shit quality, thermal unstable etc dont buy them. Price is similar to good ones decribed above.

About ECE spark plugs, I think ECE is much more forgiving which ever spark plug you choose - because no Cat.

For Cat cars spark plug operating environment gets hotter so it needs smaller air gap inside (larger ceramics in the middle - this is colder spark plug) to cool central electrode via heat conduction through larger area into cylinder head - and not to let it melt down.

Of course every Spark plug model is all about balance - because too small air gap inside and it will never reach optimal operating temperature, fuel will condense on electrodes leading to no ignition happening (misfires) from time to time and and vice versa to big gap leads to melting of central electrode or similar.

Meaning you need ECE spark plug go to Mercedes take what they have in stock.

Even if you drive 2.5 16 without CAT ECE spark plug will do the job. For CAT (and Turbo or LPG even more) colder spark plug must be used to bring it down to proper operating temp.

Regards,
Nikola.

[Marco]

Hey Nikola
For sure if I have to rebuild the engine I’ll take contact with the company from Stuttgard you recommend, do they sell also al what I need specific for the engine? Head bolt (stretched or not stretched as sometime I read is recommended), engine gaskets kit, bearings and many details as single set? Or I have to spend months to search parts …?
Any job is hard here because of lack of knowledge from nowadays mechanics or lack of parts …

By the way if I had valves damage the valves are already to replace I suppose that I continue as along I feel the engine running well at 240km/h…
Low compression can be also piston segments and not valves ?

About spark plugs ok I think I’ll be fine with H5DCO, you say ECE is forgiving because not CAT and for sure I don’t have CAT in the worst case is RUF

Timing chain: never changed for sure since when in 1992 they replaced the engine in Mercedes, it has now close to 80000km, oil I replace every 10000km (Liquimoly 10w-40 synthetic) or every 2 years whichever come first, and mechanics say that if we don’t hear rattling is not the time to do the job. But yes is there a specific km timeframe where chains must be changed regardless of personal opinions?


I assume you will suggest, and I can agree, that while doing timing chain let’s also replace the engine basement gasket, so why not valves, pistons etc?

Best
Marco

[shaq]

Hi Marco,

80.000 km and 30 years is more than enough to change the chain, I wouldn't drive it any 10km no more if I was you. Here on Forum we think that 70.000 is the right time.

It is not FIAT chain to rattle (because my first car was Uno 45 it didn't have tensioner but some funny metals on chain edges to keep it tight and mechanics check them by noise) from now on it can break anytime because every Mercedes that I know of has tensioner chain wear is measured on how long it is compared when chain was new

Same as bicycles and moto. On them there is tool that you put in chain and check, and how will you measure inside engine? No way man...

try to buy chain directly at Mercedes, there are lot of low quality chains in free shops (poland, china...)

About 240km/h was it GPS or Tachometer? Because Tachometer digital or analog from factory never tells truth. They are usually on 200+ speeds from 5 to even 10% off

By law they are not allowed to show less and they have deviation. It is never under 5% and I believe that above 100km/h it is close to 10%

So if my calculations are correct you tested it 240km/h Tacho what is real 216 out of 235 Factory (Factory declaration is GPS or RADAR not Tacho) so it is possible with that compression showed.

If you decide to rebuild the engine it will not be easy to source the parts or you will pay very expensive for them. Or both. No easy way but worth it.

But here in Germany somebody to do it for you costs up to 20k euro. Easy money for them and desaster for you

Then what machine shop will do the job for you of boring cylinders? Without tightened adapter imitatating cylinder head they will never do it right only by boring the block free standing like 99% they do.

Only those who had 16v with new/rebuild engine know the feeling how good it goes. Others "believe" that it is how it should behave and it is sad but true.

BUT on 80.000 km I believe that your pistons and block are still TOP just need to maybe regrind the valves and new head gasket of course to have again full compression.

OR if it is KAT/RuF engine it is all OK, change nothing just sparks and oil and drive. Enjoy your car.

Much more important is that compression is equal on all 4 cylinders. You showed us only 1 which is low for a ECE

Head screws are measured and exchanged only if too long.

I rebuild few engines, one engine two times and never saw a screw longer than factory spec. even if they are tightened to quite a force!!!

Smart people measure, the others they believe...

It is Mercedes of 80s the best materials used (not like today)

Regards,
Nikola.

[Marco]

Hi Nikola,

I never owned a Fiat always A.R. BMW and Mercedes but I understand what you mean, I was "just" listening what mechanics told me but ok noted your suggestion and recommendation for a chain replacement, I'll do.

240km/h was tachometer, see picture it's also something more as I see, from the power bank I remember we checked at 210 it was 205Km/h but again I'm not saying my car is faster than another, not at all, it was just to say that if I feel that engine continues this was (compared with itself) I'd avoid to open it. Except the chain job I can agree with you.

but I please ask to explain better this "so if my calculations are correct you tested it 240km/h Tacho what is real 216 out of 235 Factory it is possible with that compression showed"
You mean that tachometer shows 240 but is 216? so bit difference? so based on tolerances an healty ECE engines tachimeter is likely to shows 255-260?

Thanks for your considerations about what to do with an 80000km, regrindindg valves and new head gasket to have again full compression, I hope that this is something a normal mechanic can do withour destroy the soul of our beloved 16V...


but now some news I have today, so answering the above consider if it helps:
- contacted the mechanic, the compression test was done with engine cold!! how different can be?
- I took appointment to repeat together in two weeks, engine at 85 degrees and all four to test, any suggestions for the operation?
- source 190rev.net see the attached, we can read compression for engines when new vs used but I can not read the precise word it's stated in the official document, I suppose my target is to read 10.5 RUF or 12.5 CAT, can you read better then me?


Chain job:
Based on your suggestion never change what is working in a 40 years old Mercedes unless it's broken, so do you suggest together with the chain to replace also the 3 guides hidden by the timing case cover? I'd avoid to mess with a lot of things that are not leaking now, once for all the water pump, the SLS pump I personally rebuilt, the hose pipe for thermostat etc
And the chain tensioner I think is the correct type, why not in a factory repaired engine installed in 1992. and the chain tensioner? Better to replace also this ?
In other words I'd but the chain and the upper guide, all below the valve cover, how I see but tell me.
Time to check once more valve clearance, who sell the valve tappet set...

a lot of questions for you sorry


best
Marco
PS: meanwhile I found a nice set of n.4 factory and refurbished wheels

[shaq]

Hi Marco,

According to your Rev counter which is more accurate than tacho it was real 216-220 kmh for those revs and yes ECE should touch 260 on Tacho in my opinion when Revs are 7100 at blockade.

But I tell you my secret, I never tested max speed on my cars. I am all about acceleration and I dont trust my life such an old car at max speed because I witnessed so many accidents (even with dead and crippled people) in my life. It is not worth it...

My theory is (lot of self research and talking to many experts) up to 120 - 130 kmh whatever happens on highway, motorway in front of you or something breaks on that car you are driving at that moment, it is never "brick wall in front of you" AND you always have second or two to to do something like brake or turn aside (change line) to avoid crash, reaction with steering and tryint to avoid is much better bet than ONLY braking in emergency BUT even if crash is unavoidable and happens at 80kmh after short braking - it is still survivable.

But on 200kmh it is always fatal because in second or two of reaction time described above, car can brake to max 150-160kmh and crash at that speed is not survivable. Maybe only by pure luck in 1% the cases. Which means I am not afraid of the car, I race or speed sometimes close to 200 sometimes even more, but I try always to limit those "excursions" to a minimum, try to control myself and not to let car take control over me just because speed is beautiful and that engine has a great sound...

Fast car like fast motorbike is all about self control IMO.

Back to engine, good mechanic can do leak test without opening engine tell you where it leaks. Then you know exactly what to do, and what to expect head job or complete overhaul.

About compression this is Mercedes Workshop software (WIS) what you pictured. What it says is correct

ECE Engine also Evo2 Engine new or in good condition is the same - compression 14 - 16 Bar engine needs overhaul latest at 12.5 Bar

2.3 16 KAT/RüF Engine also 2.5 16 and Evo1 new or good condition 12 - 14 Bar needs overhaul latest when compression falls to 10.5 Bar

So your engine is either still good KAT / RuF engine or ECE that is in bad shape at the moment

My suggestion for compression test - warm engine, open full throttle, disable fuel pump (just remove pump relay because fuel washes off oil from cylinder walls and oil is needed for compression) and make sure that measuring equipment is accurate (test it with some independent tool, possibly digital for correct pressure reading)

Another thing my first 2.5 16 was so fucked by previous owner (Swiss gentleman) that my compression was 9 Bar on all 4 cylinders!

Car was so slow at acceleration that at that time to me seemed that my 190E 2.0 accelerates better.

Even like this, that car seemed it was able to reach high speed, BUT after much longer - acceleration is what was important to me, and it was bad, so for me way to tell engine has a problem!

When I bought my first 2.5 (in 2006 or 2007) I thought I married Miss Universe, but in fact it was more of Cicciolina. Everybody before me abused her and now I got her

At the end I did only logical thing, complete overhaul and some tuning. During the job I found out that 90% of the problem was Valves with little holes not closing properly at seat and worn valve guides helping the problem get worse.

But valves on 2.5 with Cat are much more abused than in ECE so I can´t say that you have the same problem that I had but - is possible.

About chain exchange, it is possible to do without removing cylinder head just break old chain, connect new with old and turn engine by hand for new chain to go inside engine and come out

Than reconnect with new pin and it is done. Of course BEFORE starting the engine check all three timing marks are in correct positions, because chain can go out of sync during process. IS VERY IMPORTANT !!!

At 80.000 km guides are still like new IMO. In my experience also at 200.000, maybe at 300.000 they need exchange.

Guides is hard plastic over aluminum and that plastic gets worn from time and mileage. But nothing you should worry about as it is quality material and lives in lots of oil. Also when valve cover is removed mechanic will se how much it is worn - new is straight surface and from mileage chain make path in plastic, if path is too deep it needs exchange and it is done trough front cover again engine is not opened (head removed)

Like said above Mercedes chain has tensioner, plastic guides and therefore it is silent, not Fiat like my car when I was 18 which rattles new, rattles old and mechanics tell difference by noise

They must be magicians

Like I told you, do important things chain, oil, spark plugs and just relax. Drive car as much as you can (when you are back home) and try to learn soul of that car

Enjoy your car, it is meanwhile old lady is not so important max speed or Dynojet. I mean you had luck driving 240kmh with old chain, if it broke at that moment you would need new engine like previous owner did.

And most important thing - I told you above how race engines rev 9500 RPM but engine lasts only 1200km.

Always remember that what Mercedes said in one commercial "Maximum speeds are more theoretical - they are not designed to be used. Most important is good acceleration and powerful brakes - it will give you ability to safely overtake and use gaps in traffic denied to all other drivers"

Which translates into, yes car can handle a lot but harder you push, the shorter lifetime will be. And never push cold engine.

Engine is cold until you see on Oil thermometer 80 Degrees in central console. Just water in Tacho above that reaches 80 Degrees is still too cold engine !!!

That engine had lot not casted but forged parts and they need correct temperature to reach its proper and operating dimensions.

Bye,
Nikola.

[Marco]

Good evening Nikola,

“Limit” this is the wording I was not able to read from the WIS page! This I understand now after reading your reply on the compression. So limit after that engine needs overhaul. Thanks

Compression test: yes I had in mind to take out fuel relay, to avoid also HV sparks: remove plug from HV coil to distributor cap and/or EZL plug from crankshaft position sensor?
…for the accuracy I’ve to trust instruments mechanic give…
I’m wondering how much different can be warm engine vs cold, but yes he said he has another manometer for these tests and he doesn’t know the accuracy of the first he used… but I suppose we are not moving far from 1/1,5 max bar of differences, plus or even less. Let’s see.


Chain job:
Meanwhile I’ll pass in Mercedes to order new chain I think this is at least not a complicated job, replacing the chain only, assuming they sell it, only Febi is on the market as alternative….can you please revert to following points from my afternoon’s reply:

never change what is working in a 40 years old Mercedes unless it's broken, so do you suggest together with the chain to replace also the 3 guide rails and the tensioning rail? They are hidden by the timing case cover? I'd avoid to mess with a lot of things that are not leaking now, once for all the water pump but not limited to …
Please have a look to the picture of the chain tensioner I think is the correct type, why not in a factory repaired engine in 92 when they had this component redesigned already from some years. Can I keep it?

Have a nice evening
Marco