s class

Hi guys,

I'm new here. I've owned my 1992 500SEL for a year now. I've replaced ignition leads, caps, rotors, coils, plugs, throttle body, all inlet gaskets and seals, breathers. Fuel pressure and flow are all in spec. The injectors have been ultrasonically cleaned and tested for flow. I still have a misfire that occurs when the car is warm, at low engine speeds. Its fine when cold. I have found that my compression readings are :

65 to 75 kPa with engine at temperature, cylinders dry.

readings rise to 110 to 120kPa with wet cylinders (oil inserted into cylinders).

This all indicates problems with the rings, cylinders or both.

I've had the sump off and the cylinders look OK, no obvious problems, and an acceptable lip.

Does anyone have experience with such problems, and any rebuilding experience? I know that the cylinders have some special coating, so reboring is not a simple matter.

Thanks, Ryan in South Africa.

s class

No replies?

I'm assuming you are all thinking "poor bugger". Well I will be poor after all this. The lesson that all can learn from is that I bought my W140 cheap, which isnt necessarily a bad thing, but the mistake was not checking out the engine condition thoroughly first. Really, these engines are so expensive to fix, I would recommend that if you are think ing about buying a W140/129, you MUST first get a compression check and scan of error codes.

Ryan in South Africa.

sk217

I don't understand thing like that:
I only understand European measures.
That's not news.
I thought that is a MUST on any car your are buying.
What else can I say? Ofcourse it is too bad that your Mercedes is having problems. As far as I know, if the compresion is low, start saving money for an engine rebuild.

s class

Sorry I made an error in my orignal post, the compressions should be 650 to 750 kPa and not 65 to 70. Likewise, the wet compressions are 1100 to 1200, not 110 to 120. Sorry for that.

I have since found that the compressions are higher, say 750 to 850, when the engine is cold, compared to the 650 to 750 when hot. I think this may explain why the car goes well when its cold, and only starts to miss when it gets up to normal operating temperature.

Yes, I know the engines are very expensive to fix, its not news to me either. I have the budget, I was however wondering if anyone else had been through this themselves, and could share some experience.

The car is otherwise sound with excellent transmission and flawless interior. No rust issues either. I have rebushed the suspension and overhauled the pump. The rear struts are fine, though I will soon think about spheres.

Thanks, Ryan

sk217

You can get rust in South Africa?

kwb210

First I would simply drive it and add cheap oil to keep it alive, I had a 300D that had almost no compression in 1 of its cyl. It used oil at 2 quarts to 750 miles for 8 years. It simply never got worse. I babied it and actually did not use cheap oil. The longer it lasts the longer you have to look for a car w/ body damage and a good engine. I believe there was one on ebay.
Keep us posted.
kurt

sk217

Diesel engine is very different. Yes, on a diesel engine with almost no compression you can drive forever, but your strategy would not work on a gasoline engine.