190e 2.5 16v - Cylinder Head Overhaul

[Limespyder]

I have a 190e 2.5 16v which has been giving me problems. It has had various faults all to do with idle and cutting out. I have replaced injectors, fuel pump 1st stage, had the fuel head recalibrated, new cam chain, adjusted tappets. the list goes on. Anyway the point to this posting is that I discovered once the tappets had been reset (Exhaust valves where tight). That the engine is down on compression on three cylinders and after a wet test it has been decided that the exhaust valves need some work. The car now runs reasonably well only cutting out occationally and only usually when cold but the main problem now is high hydrocarbons and thus needs to be repaired before the next MOT.
So.....
1. Has anyone done this before and are there any potential pitfalls in the head removal ?
2. The only manual that I have been able to find on this car is from this site.. But covers the 2.3 not the 2.5 as the data that I have found thus far seems to point to the only differences between the engines is in stroke will this manual provide the information I require to rebuild the cylinder head ? and if not what are the differences that I need to be aware of ???

 

[Andy]

190e 2.5 16v

Hi

I am sorry to hear that you are having so many problems. The 2.516v is usually quite reliable. Although I must say if you have replaced all the parts listed. To cure the vehicle cutting out. You should of visited the forum before. I would of told you not to waste your money. If I may be so blunt. I would take to some body who knows what they are doing (sorry. but some straight talking is what's needed). If you look through this forum under "my vehicle's cutting out" etc, or 300e keeps cutting out. I have mentioned getting the KE system checked out. This applies to your vehicle also. Although the idle control valve gives trouble with these 16v's but not always. So I would get some body to check it out thouroughly.

You mention the tappets where tight. The tappets on your vehicle are shimmed. It is unusual for the tappets to go tight. So I would expect that somebody has been messing with it. If the tappets are tight. Then usaully the engine will be lumpy on tick over. Which could cause you hydrocarbon problems. But before we tackle the hydrocarbon problem. Before I would go taking the cylinder head of I would remove the camshafts. This way we can be assured that the valves are fully seated. Carry out a cylinder leakage test.(For those of you who are regular readers of these forums. You will know I am a big advocate of this test.Why? This is by far the best way to tell the condition of any engine.) If your garage cannot carry out such a test. Then take it to one who can. If the test then shows a high leakage, then take of the cylinder head. IF they have carried  out the test correctly. You will know EXACTLY as near as damit what parts will be required before the head is removed.

For the lay men reading this. Hydrocarbons, are unburnt fuel. This is measured with a four gas analyser, during Mot tests, and anybody carrying out any sort of engine tune. If you can't read all four gases coming out the rear,especially on cat cars. You are wasting your time. The correct reading and evaluation  is imperitive for diagnostics.
Anyway, you have mentioned that you have had most of the injection system replaced. Ie, injectors,metering head reconditioned?!?!?, fuel pumps. If you find that either the cyl leak test dosn't show a huge loss. And the tappet clearences are correct. Then you will have to retrace your steps. If there is loss as you mentioned then this could cause high hydrocarbon readings. But make sure you have carried out the basic test as mentioned before taking of the cyl head.

You ask about pitfalls. There are many to the inexperienced. 16valves to start with.

The 2.3 manual shold get you through it. The 2.5 has a duplex chain. The timing chain tensioner is a little different also.

Hope I have been of some help, if required you can contact me on the url below.

Regards
Andy @www.mercedeservicing.com