Compression Test on W124 '90 300E
 

Hello,

I have a 300E with 110,000 miles on it. I get grey smoke from the exhaust between idle and 2500 RPM. I read that this could be valve seals. I did a compression test and each cylinder did the exact same thing. I did three strokes of the engine and the readings (in Bar) were: 9-10-13 on all cylinders. I understand that 8.5 is minimum for these engines. According to Haynes if a reading starts low and then jumps the rings are suspect. But would there be such a coincidence that all six pistons have worn rings? So far, does it look like the valve seals could be problematic? And finally, approximately how much is a stem seal job?

Thanks, Andrei

Have you tried adding a bit of oil to each cylinder and repeating the compression test? If the readings are drastically different (better), that should indicate the rings need renewal.

Wet Compression test?
 

So that's what's meant by "wet" compression test then? I'll do that ASAP and post the results.

Fuel Pressure Regulator hose leads to nowhere.
 

I should mention that the fuel pressure regulator vacuum hose is connected to the regulator then there is about 8 inches of hose and then it just hangs there broken and not connected to anything.

Should be connected to intake manifold vacuum ( BELOW the throttleplate ).
Also, when you do a compression test, do it with the throttle WIDE OPEN. ;)

I did do it with the throttle wide open. When you say below the throttle plate, what is a throttle plate? Throttle body??

Yes. ;)

Thanks, I'll check it out. What are the effects of this hose not being connected?

Never heard of "grey" smoke. There is blue smoke if it's burning oil, black smoke if it's running rich, and white smoke from normal condensation after a cold start or from a blown head gasket. Anyone add to this list of smoke colors?

Like atikovi said, I've never seen grey smoke being emitted from an engine.
With only 110,000mi, it would be extremely unlikely the rings are worn. These engines generally go well over 250,000/300,000mi before requiring any engine word (except valve train), assuming it has received its normal dose of regular oil change
Valve guides and/or valve seals are a possibility, but still, you'd see blue (not grey) smoke if it was the case and your oil consumption would be way up, like a quart every 500mi.

you can get grey smoke
 

from unburned fuel in a gasser.

like when you stomp on the throttle on the highway, so you prob can get it at slow speeds too.

tom w