Leaking valves?
After noticing that my engine wasn't running as smooth as before (3ltr l6, OM603 non-turbo -you know the sluggish one) I've had it pressure tested last week. Compression on cylinder 1 is about two third of the others. A wet compression test suggested a leaking valve and that turns out to be true. So now I'm having the head done (valves, seats etc.) But I'm wondering what could have caused this. The OM603 non turbo is supposed to be one of the most durable engines around. The mileage on this one is relatively low, I've had no overheating problems and I'm usually not pushing its limits. Any ideas?
Probably once the head is removed, you might find the cause:
lack of lubrication, dirt or debris under the valve, valve guide, bad valve....
Anyway, you didn't say exactly how many miles the engine has done?
The other thing could be that if driven too gently, it might build up carbon deposits in the wrong places.
what temperature reading do you get at 4200rpm over the distance..to keep the deposits to minimum it should be around 95c.... just under the line above the 80c ..injectors not set up properly will cause deposits as will faulty heater plugs...diesel that has been "doctored" lacks lubricant with adverse effects..if that happens in Holland!!!
If you are taking off the head, it would be a good oportunity to change the hydraulic elements. They open the valves via the camshaft. £12 ea 2y ago.
Don't worry about reving the engine, it will not cause a problem. Altering the gearing will turn it into a real slug.
Running at high revs produces about the 95 degrees C you mentioned, a little over that in hot (30 +c) weather. The injectors were tested and are ok. The mechanic working on it also mentioned changing the hydraulic elements in one go. Picking the car up next week, hoping for a silky smooth ride -and an added 150 bhp but chances are slim:-)
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The engine has done 120.000 kms according to the counter (which I find doubtful for a 15 year old car but according to the previous owner and the MB mechanic it could be right). The exhaust valve on cyl. 1 doesn't close properly because of carbon deposits. The other valves suffer from the same problem but much less so. I figured that since the engine has to work pretty hard in this car anyway this was not likely to happen. I mean to drive 135 km/hr on the motorway it revs to 4200 rpm. So I'm wondering what I need to change in order to avoid this problem in the future.