Sick Diesel engine - need help

Synkro

Hi All

I have recently purchased an 1982 Mercedes G-Gwagen. Ive been told there is backpressure in the engine, and as a result it is blowing out oil. The engine is a 3Ltr W123 (Type 617).

Would anyone here know of a good diesel engine specialist who could give me an assessment? Ive been offered another engine but will be costly to swop.

Would like to know the extend of damage, and approx costs to put right.

Cheers.

MercMad

Well pretty much any mechanic will do a compression test on it, once he has a suitable gauge. get a leakdown test done also to determione whether its bore wear or cylinder head/valve issues.

Compare the figures to the manufacturers spec and then decide. Rebuidling that engine would definitely cost a few bob but buying a used engine could be as much trouble, unless you again do the above tests on it prior to purchase.

Where are you based ?

Synkro

cheers mercmad. That's good advice. I'm based in dublin15. Compression & leakdown would seem like a good idea. I have another w123 which vibrates quite a bit when idle, would that be an imbalance between strokes? It's grand when I bring the idle revs up a bit

oflynno

as that man said,begin at the beginning and get that testing done
it will rule out valve failure and piston rings and all that

at minimum the head will have to come off but thats not the end of the world

let us know what happens,it sounds like a valve stuck,but i have been wrong before....once

MercMad

Synkro wrote: »

cheers mercmad. That's good advice. I'm based in dublin15. Compression & leakdown would seem like a good idea. I have another w123 which vibrates quite a bit when idle, would that be an imbalance between strokes? It's grand when I bring the idle revs up a bit

................is the W123 Petrol or Diesel ?

Either way it could be missing at idle, if petrol check the usual basics, plugs, leads, cap & rotor. After that check for vacuum leak from hoses/vacuum pipes or if carb'd check the carb gaskets.

If diesel its more likely to be an injector problem, most likely dirt or build up which detroys the spray pattern, or leads to overfuelling at idle. I would run some fuel cleaner through it.

Good luck.

andreas_220D

MercMad wrote: »

If diesel its more likely to be an injector problem, most likely dirt or build up which detroys the spray pattern, or leads to overfuelling at idle. I would run some fuel cleaner through it.

Keep in mind that the engine/car is now ~ 30 years old, so the engine rubber mounts are likely much softer than they are when new. And the good old OM615/616/617 is heavy and of a rough nature.

It's normal that they vibrate a little when idling. Since the vibrations disappear when revving up, i wouldn't worry too much.

As to the injectors, if they have never been replaced they are probably EOL after ~ 30 years. A new set of modern ones used in the W124 e.g. is not that expensive and worth the money (i did that on both my diesels and haven't ever regretted it). I'm not fond of fuel cleaners since they cannot repair worn out injectors. Remember: the avarage lifetime of an injector is 100000 km/60000 miles. The workshop manual recommends injection pressures from 115 to 125 bar. In old worn out injectors the pressure can be down to 90 bar which results in a too early injection and thus causing the engine to run very rough and loosing power. I have some nice examples of worn out injectors at home :cool:

Also, the valve timing (is that the correct term?) should be checked. I'd recommend to do that at least once or twice a year.

Well, to cut a long story short, you'd have to see and hear the engine for a diagnosis:D

MercMad

andreas_220D wrote: »

Keep in mind that the engine/car is now ~ 30 years old, so the engine rubber mounts are likely much softer than they are when new. And the good old OM615/616/617 is heavy and of a rough nature.

It's normal that they vibrate a little when idling. Since the vibrations disappear when revving up, i wouldn't worry too much.

As to the injectors, if they have never been replaced they are probably EOL after ~ 30 years. A new set of modern ones used in the W124 e.g. is not that expensive and worth the money (i did that on both my diesels and haven't ever regretted it). I'm not fond of fuel cleaners since they cannot repair worn out injectors. Remember: the avarage lifetime of an injector is 100000 km/60000 miles. The workshop manual recommends injection pressures from 115 to 125 bar. In old worn out injectors the pressure can be down to 90 bar which results in a too early injection and thus causing the engine to run very rough and loosing power. I have some nice examples of worn out injectors at home :cool:

Also, the valve timing (is that the correct term?) should be checked. I'd recommend to do that at least once or twice a year.

Well, to cut a long story short, you'd have to see and hear the engine for a diagnosis:D

............yes thats all good advice, I figured since the OP has other diesels that he would be familiar with the vibration at idle, and that he felt this engine was not normal.

If you could determine if there is a definite "miss" at idle, by looseing each injector whilst running that would confirm which cyclinder is at fault. You could then swop injectors and see if the fault faollows the injector or stays in the same cylinder, indicating a compression problem.