2.5-16V rebuild Info

[Cloudini]

Dear 16V friends !,

im up to rebuild my 2.5-16V engine, upcomming summer, until then i thought it would be wise to look and ask for some information, like is there anything to be carefull with and maby someone could tell to be caution with this or that ?
i have no idea if there is any walkthrough/tutorial arround on the internet,

maby someone could share his or her story,

tnx
Wesley From Holland

[shaq]

Hi there,

I rebuilt three 16v engines so far togethet with a friend who is mechanic, its not some big experience but I noticed a few things:

1. The most work is to be carried in cylinderhead as there the most wear occurs
2. Also chain mechanism for camshafts is to be closely inspected / changed weared parts
3. Rebuild oil pump its a must, also change crankshaft bearings
4. Minimum change piston rings and connecting rod bearings even better are new pistons in reparatur size
5. Dont believe or assume that something is still good but measure everything and compare with specs.
6. Keep in mind that like there is no two humans exactly alike so there are not two engines.
What I mean even with same mileage depending on oil quality, No. of cold starts it was subjected to, repairs and tuning etc. there can be enormous differences so nobody can tell until its dismantled. Then take everything apart, measure each component and ask here if there is any doubts.

Regards,
N.

[Cloudini]

Dear Shaq

thanks for your Reply, so far the Engine's Cold start is fine, but the Engine itself is using oil, together with white smoke from the exhaust and an Pretty awefull smell like oil/coolant water is burning, the inside of the car starts to stink too because of that,
could be just the Valverings that is leaking oil, but probably the headgasket is broken to, so i thought if i need to take the head of, why not do the entire engine for the sake of it,

anyway its until upcoming summer, when the garage build is finished than ill remove the engine from the car and start opening it up, i just thought it would be wise to hunt down some information in the meanwhile

so thanks for your reply

im not scared about ordering new bearings for the crankcase and for the piston rods, but more into where shall i order if needed new piston rods them self and new pistons with rings, im not sure if i need to order factory size pistons or Oversized, it all depends on the wear it has inside the engine, are there still OEM pistons for sale ?

i did an compression test
Cyl 1 had 12Bar
Cyl 2 had 9 Bar
Cyl 3 had 10 bar
Cyl 4 had 12 Bar so there is clearly something wrong between 2 and 3

its on 232.XXX KM on the cockpit

[shaq]

Hi Wesley,

Where are you based in NL, I have a brother living with his family and children in Rotterdam since 1992. Been visiting him, wife (she is Dutch) and boys for couple of times

Based on my experience when one has 2.3 or 2.5-16 with 2xx.xxx km or more & engine problems (oil consumption, lower compression) and when one would just take cylinder head off and replacing it with a new one / a rebuilt one all the problems would of been solved in 9 out of 10 cars. Of course assuming that KE Jetronic is OK and well tuned and that valve-chain mechanism is OK. Don't worry about your head gasket (yes they also can get damaged in 16v's) as replacing / removing cylinder head means a new head gasket every time (cca 100 euro)

Always remember that the head is the weak point after all those years in 16v and much less likely the bottom part (engine block). Also inside the head the greatest wear occur on valve guides, valve seals, exhaust valves and their seats. In engines I was dismantling with a friend intake valves were always perfect as their seats were too. Intake guides had also way less wear compared to exhaust ones. Exhaust valves are under much more stress and also Mercedes-Benz factory themselves was wandering around which to choose during production years (as with chain tensioner, that was the same case) changing part numbers 3 or 4 times and using different grade materials as well as shape to cure the problem! Now standard exhaust valves for all 16vs are Evo II valves

Connecting rods as well as crankshaft are forged there is a little or no chance to damage them in standard 16v engine as long as there were at least 2 liter oil in the system (out of 5) and engine is not modded to rev past 7500 rpm. Pistons are also forged and Mercedes engine block is also high quality and rigid

Also when you measured compression you should do it right away the old school way*:

1. Measure compression write down value for single cylinder
2. Remove compression gauge, put through spark plug gap a few drops of engine oil in a single cylinder (not more!!! don-t pour oil and be careful)
3. Put gauge and measure again the same cylinder, compare readings to 1.

Result>
Difference up to 0,5 bar so piston rings are still very good and compression loss (if any) comes from valves not closing correctly
More than 0,5 bar piston rings are also either worn or with lots of carbon deposits on them (bad piston rings for sure)

* Trick comes from VW Beetle service manual from 60ties. Ever tried to repair hand bicycle pump yourself with a grease when rubber piston is worn? The same prinicple occurs here, that oil seals piston rings and for few engine turns sealing between piston and cylinder is perfect just enough to take measurement. Compression tester has non-returning valve so even if compression drops later on it will show max. value for which we care and which shows us what we need to know.

Also other method to trace blue smoke, that's when engine consumes oil is make someone drive behind you on open road and then accelerate with 2/3 throttle to 4000 or 5000 rpm and then quickly release throttle pedal for a second or two, and then depress pedal again to the floor. If there is a cloud of blue smoke that's the oil coming through valve guides/valve seals. If not they are OK. Also you can do it yourself by observing the rear view mirror when depressing pedal to the floor after it has been released but be very careful that way is more dangerous

If you look to some of 16v Hockenheim videos at YouTube there is to be seen exactly what I described above on car exiting sharp corner

Bad piston rings
In case of bad piston rings (which could be a sticky oil ring as well, not necessarily worn out) the oil remains on the cylinder wall while the cylinder is firing. This means the oil is burnt as well as the air/fuel mixture during normal driving.

Bad valve seals
When decelerating at higher rpm you have a closed throttle which generates maximum vacuum in the cylinder. This vacuum sucks oil via leaking valve seals into the cylinder and as soon as you accelerate again this oil burns causing blue exhaust gases. The longer you "decelerate" = keep the throttle closed the worse it is.

Also remember white smoke comes from lean fuel (also clogged injector) or coolant entering cylinder, blue from oil and black from too much fuel (also leaking injector). Also different types of smoke smell differently one like rotten eggs, other like a 2T scooter or all together but better we leave smell alone

Conclusion> as one can do various tests when buying a car (compression, oil leaking in cylinder, compression loss test, endoscope, this test with deccelarating etc.) to be able to see what the real condition of the car is and not to overpay it, I think that you based on all what you said need to dismantle that engine anyway (first the cylinder head what can be done while engine still installed in car). Now if you do not plan to raise the power in future using serious but very expensive tuning and after results of repeated compression test (that with oil drops) shows that the rings are still good you may leave the bottom part alone and be happy with it. Also when cylinder head is off, and bottom in its place your mechanic will see what is condition of cylinder-wall by looking at top of it and to feel (or better measure) how much wear is there.

So now here is my advice:

If you like your 16v as it is, it is not your main car (it is a weekend, joyride car etc.) and you travel with it less then 5000km pro year (many of us not even 2000). If bottom don´t shows signs of major wear rebuild just the cylinder head and you will be happy with the result.

If you are up to tuning in future, even mild one, you must at least change rings and bearings now even if everything is still in specs. After more force is applied to used bearings they usually start to "sing" very soon. New pistons would be even better and of course they are must if current pistons / cylinders are out of specs.

Pistons are still to be found at Mercedes, but count on 1000 euros for them alone. Yes they come already with rings. Changing rings only will set you back from 100 to 300 euros set depending on where you find them and on discounts. Bearings for rods are about 30 euros a set. Decide now if you will go for tuning is it going to be even a turbo or compressor as for those applications you need different pistons which lower compression ratio and maybe some other parts and remember one the thing nobody wants is to do the same job twice or to have to buy the same expensive things like pistons twice in a short while.

Regards,
Shaq

[Cloudini]

Dear Shaq, First off all i want to say i feel really Blessed, amazing how much Info you just gave me thank you so freaking very much man !!!

i went to a shop and bought myself an Compression gauge, i went to an dealer before and let them do a compression test, but they didnt do anything with oil,
so what i get is basicly when i do an compression test first without any oil, write that down, do it again with a few drops of oil (an thea spoon maby ?) and compare that to my first test, either if the result is the same as FOR EXAMPLE

Cyl 1 12 bar
Cyl 2 9 bar
Cyl 3 10 bar
Cyl 4 12 bar, without oil

and its the Very Same or slightly Higher with oil, its an Valve issue because compression is escaping true the valves, If not and it gives me an total Diffrent result like

Cyl 1 12 bar
Cyl 2 12 Bar
Cyl 3 12 Bar
Cyl 4 12 Bar kind of Result. it means the piston rings are worn out,

i do need to keep in mind that because of the low bar range between cyl 2 and 3, this could be just an Gasket leak ? explains why my car has white smoke from the Exhaust, with bad smell, its an very doesnt smell like rotten Egg but more like an Overdosis of Suger, hmm well not sure how to explain that one,, Also , Cor De Jong From Bergambacht (mercedes Dealer Gruyten En De Jong) he used to go to w201 16V evo meetings in germany too !, walked arroud my car, with an running engine he lifted the Oil Cap on the valvecover and there was white smoke coming out of there too, but hopefully its an valve causing the Oil drinking, ive drove like 5 monthes with my car, and it took 60% oil out of the engine by just driving it.

anyway i dont really see any point in replacing pistons and bearings to an engine wich has perfect compression, maby in the future later when the speedometer goes to 3XX.XXX or 4XX.XXX ? well that doesnt even say anything either, just to have an Fresh engine again. feels more selfesure, im never ever going to heavly tune the Engine, i dont think its worth it anyway, MABY MABY sometime ever, an DTM kind off Intake, EFI something maby ? not sure about that anyway. but the huge Carbon intake box looks and Sounds Really Sexy hehe

i havent used the Evo II replica for this summer so i have the battery on the charger for now, and try this all out tomorrow.. ill post my results for sure !

and next to that. i live VERY Closely too Rotterdam like an 30 Minute drive towards the coast, (Rockanje, Oostvoorne, Brielle, Spijkenisse) so feel Free to meet up sometime

Once more thank you for your Time so far highly appriciated !
Wesley

Edit: I found an old video i took a while ago, sorry for the upside down filming but, here you can see the smoke its giving with an warm engine temperature !

[shaq]

Yes about a teaspoon then you will know at least something about condition of pistons/rings.

Also if you plan to rebuild your cylinder head let it be hydrochecked for eventually micro cracks in aluminium.

I dont think that lower compression on 2 and 3 comes from blown gasket i would rather say it was valves not closing sealing perfectly

PS if I come again to NL (not planned soon) I can see that in person

Nikola (Shaq)

[Cloudini]

so i did an compression test today, first Dry than Wet with oil, also took pictures of that with at the end pictures of the Sparks , they all look brownish with black

anyway this is Cyl 1
Dry

Wet (Oild)

Spark


this is Cylinder 2
Dry

Wet (oild)

Spark


Cyl no 3
Dry

Wet (oild)

Spark


Cyl numbero 4
Dry

Wet (oild)

Spark


To be honest, i find All cylinders kind of weak. i believed an fresh 190E 2.5-16 Engine should have 12 Bar per cilinder right ? this is what i found on the internet * 2.5-16 compression ratio 9.7:1, new value 12-14bar, wear limit 10.5 approx. *
your thoughts ?

Wesley

[Christhunter]

Compression is much too low.

[shaq]

your cilinders and pistons are in a good shape according to this test!

I see nowhere more than 0,5 bar difference

problem as assumed is cylinderhead, valves leaking in closed position a standard issue with 2.5-16

think of it that all cylinders are leaking and 2 and 3 more than the others thats it...

also did you test it hot or cold engine? Is battery strong enough to put oil pressure to 3 bar in dashboard while you were doing tests. was full throttle depressed and fuel pump relais removed as gasoline washes oil away when no spark is present which is not good for compression

Anyway my opinion on this is that block is still OK.

seems that because of Vorkats (those Cats close to engine) exhaust valves got burned on 2.5-16 and evo1 and when you remove valve and closely inspects contact area you see a lot of tiny surface-holes and thats exactly the spot where compression is leaking. I dont mean here burned valves with hole in them like you often find in opel and fiat, but surface holes just like orange skin metal in important area that should be as even as possible.

Evo2 dont have this pre cats anymore and it is wise to remove them out when doing rebuild (see Fränks post and his solution to this problem)

On my 2.5-16 I have over 13,5 bar on all 4 cylinders after rebuild and it goes like hell compared how it performed before (yes I have compression about as yours dont remember exactly but it was under 10,5 bar for sure but was even on all the cylinders) but now special procedure for starting up the engine, no more cold starts, no fuel and no spark delivered to the engine before oil reaches 3 bar


BR,
Shaq

[Cloudini]

Hey Shaq,

well hmm i need to redo this test than, what i did was
unplugged just the sparkplugs and my buddy was behind the steeringwheel with the ignition key and the foot pedal to the metal, so yes throttle was open all the time, on the otherhand I DID NOT removed the fuelpump release, and i did not pay attention to the oil pressure to 3 bar,

engine was arround 60 celcius water temp. let the car idle for 10 min or so,

when i bought this car, the engine already had these simptones but i didnt bought it for that much money anyway, the outside is an Pretty niceley done evo 2 replica (no rieger parts)
but the cars exhaust already had the cats removed both front and rear cats, so maby the burned valves has come from before,
there is a lot more problems to the car to solve, like leaking rear shocks (the sls system) but i dont really care, i like too restore the car and fix all the problems. engine mounts are flat too, the axle from the gearbox to the diff center has space too so i need to find an replacement too but for now the engine itself is priority !

but burned or leaking valves also clears up the problem of using excesses engine oil too ? and did you went from 10,5 bar something to 13,5 bar AFTER just an enginehead rebuild ? WAOUW ! that sounds really tempting for me now hahah !

again thank you so much for your effort and time

[shaq]

I think you dont have to test it again, it won't be much different and I think you saw the point. also these other cylinders 1 and 4 I am positive that their valves are also not brand new anymore in terms of sealing but yes they are much better than 2 and 3.

But you know what 2 and 3 are one pair. They share the same pre cat so that one seems to be clogged man and afterwards valves got burned. Good that they were removed.

No I didn't do only head rebuild I changed also piston rings and Conrod bearings, however when we measured pistons/rings/cylinders it was still in specs so I dont know why we changed them after all, but when everything was out - its was a pitty not to put at least new rings and big end bearings as I was planning some power increase in future. Also my head got ported during rebuild as it is the heart of engine, there happens or magic or notings happens at all... (but if I was to keep it stock rings and bearings probably weren't a must at least for my engine at the time).

Engine got a new clutch and seals so that was it, but most of the increase in compression came from valves in my opinion. Also did the same job afterwards to a friends car (he is a first owner have bought her new back in 1992) only did head job and car was again in all its glory higher compresson = lower consumption and more power...

[Cloudini]

hmm,
its sad the weather has turned into crap lately, otherwise i would remove the head and check in what condition the cylinder itself is, better wait for this all until the garage is finished,

what about the oilpump at this stage ?, should i concern about that, or even check that ?
,


greetings
Wesley

[shaq]

No, oil pump is to be resealed if everything is taken apart. For headjob its not a must but chain tensioner and its gear sure is.

How is your oil pressure on warm engine?

[Cloudini]

oil presure is at 3 with an hot engine,
im not sure if the oil presure sensor is still ok?,

i heard something that it has to go back down to 2 something maby ?

greetings
wesley

[Cloudini]

Soo, plan Changed Bigtime !,
last wednesday, a buddy of mine called me up, he said hey be aware with in 1 hour there will be an friend of his that was going to drop an engine crane, i was like wtf ? well oke

than this guy dropped it off and said here, your buddy called me to bring you this thing for your engine. i was like cool but how long can i barrow it ? he said 2 weeks than i need it back. so i was like wtf ?, anyway i had this week off so i said. u know what leave it here. ill replace my engine mounts, so , during the job i replaced my engine mount but at one mount i had to remove the KE jet tronic system, there was 1 bolt that didnt came lose and i had to work all around, now that the intake manifold is of. im going to remove the exhaust and remove the head !,

any tips on this ? like timing chain ? (i do want to replace the timing chain for the sake of it ! i dont know how old it is,) any tips on that how to replace that one ? and i need to becarefull to not let it drop inside the engine,
with replacing the timing chain, do i need to replace the camshaft wheels ? (my motorcycle technoligy kicks in) replacing an chain together with the front and rear sprocket wheels.

is the chain tensioning rail easy to replace ? if needed

is the valve timing from an 2.3-16V the same as the 2.5-16V ? cause im using an 2.3-16V workshop manual
and what are the valve clearances intake and exhaust ?

since im using an 2.3-16V workshop manual. all the Nm bolt tensions are the same for the 2.5-16v engine aswell right ?
sorry lol. first time im doing an Car engine, but there is an first time for Everything, this is awesome learning stuff aswell !

thank you so far !!!!!

[Cloudini]

Oke

so i came so far that ive removed the cylinderhead, and this is what i found, All Cylinder walls had the bore lines in there so they looked pretty fresh at first sight, but after closer look. it was aspecially noticeble on Cyl 1 but i believe the rest have it too and i dont know if this is OK or not ?!, the Piston seems to lean to 1 side of the bore more than it is perfectly center, please let me know if you understand what im saying, (there is more space between the cyl wall and the piston on the intake side than on the exhaust side) im not sure if this is OK

hope picture tells more about the state and so on, there are light wear noticeble to be honest, and there is an scratch on Cyl 3 on the Top near the gasket.

Cylinder 1




Cilinder 2




Cilinder 3




Cilinder 4




what shocked me the most was so much carbonite soot on the intake valves ! more than on the exhaust valves. whould have expected to be equal or the same on both sides.




i will shoot pictures of the valves them self tomorrow, need to find my valve clamp,
but i hope some one can tell me that the piston that is out center by very VERY VERY small diffrence is an huge deal or not ?
maby thats why the wear on the cylinder wall is just at 1 spot.
the state of the cylinder walls ? is that acceptable even with the wear spots ? does the very very slightly sign of wear tells me to replace anything ? like piston rings or so ?


thanks so far
best regards
Wesley

[db16v]

Hey Wesley.

Your Cylinder looks not soo good.
There are grooves in each cylinder.
I think your piston rings are in a bad condition too.

The best is when you put the pistons out of the engine and take a look of them.

Greetz
Thomas

[Nagilum]

IMHO it's time to bore the cylinders and get the next bigger pistons.
Just changing the pistonrings won't be acceptable for me!

Regards
- Christof

[Hubert]

I think this engine was raped by the ex-owner(s).

Rebuild it fully, the effort will be worth.

[shaq]

Deposits = come from oil consumption and other factors (many short rides-engine still cold)
If that engine used coolant as well they would be clean as new. The coolant would of wash it out.

Gap between cylinder and piston is quite normal as
1. These are very big pistons
2. They are forged (larger coefficient of expansion when hot)
3. Same thing you can see e.g. on E34 M5 gap cylinder-piston is big
4. From pictures nobody can tell go measure

Good is that man can still see honing lines in cylinder as they hold oil when piston goes up and down, bad is that those vertical lines are to be seen as they cut honing lines who hold oil at the first place and also can tell that engine was driven hard cold also before piston had a chance to completely expand so piston was banging side to side and made those lines.

But I dont know is there any 16v out there completely w/o them. Maybe that one in Museum with a brand new engine

That one deep scratch is no good that was some big mess entered that cylinder (K&N?)

However the biggest problem on that engine are valves on the first place in my opinion and your compression tests showed it. Rings/pistons/cylinders are not perfect but also not that bad look at it as this new rings and big end bearing would be good for next 40-50.000 km and new pistons / overbore for next 100.000 but will cost much more. You best know what are your plans for that car...

BR
Shaq