MBWizard

I have a 1995 SL500 with 73,000 miles. I have a recurring problem with moisture under the distributor caps. O rings are not the problem and I doubt the cam seals are either. No oil leak and no petroleum odors adhering to the inside of the cap. Research here has suggested a possible clogged pcv valve causing higher crankcase pressures but I still don’t have the telltale odor. Since this is a recurring problem, about every 6 mos to a year, I thought that replacing the valve might be worth the effort. Local parts (I don’t have a dealer locally) have showed me what it is supposed to look like, however I can’t find anything similar looking. Other research seems to indicate the the M119 engine doesn’t use a PCV valve, which I find odd. I am open to suggestions. For the record, both a dealership and a local qualified repair service have looked at the problem with the same solution, replaced the rotors and caps, an expensive solution for a car that doesn’t get driven that much.

MBWizard

I believe I may have found the source of the moisture. I removed everything down to the end of the camshaft and noticed that the backside of the distributor lower housing was covered in what looked like water but had a mildly greasy feel. This seems to confirm that the camshaft seals are starting to show their age. I’ve ordered replacements (easy to replace) but would still like to identify the pcv valve. Like I said earlier, the picture of the part at the auto parts store doesn’t match anything I recognize under the hood. I’ve also checked parts geek which show a pcv hose but no valve. I’ve found that part under my hood and it does connect to something that vaguely resembles a pcv valve.

grege

MBWizard, how did you get on with this, has it solved it? I keep wiping mine clean of moisture but if its easy would be worth fitting seals. Did you have part numbers and prices you paid?
Thx Greg

mahunt

I don't know about the V8 cars, but the V12 has a metered vacuum port in the passenger front valve cover.

I too had internal crankcase pressure build-up, but didn't know the source. I only discovered the vacuum port when I removed the valve covers to have them powder coated. In the V12's case, it's actually twin metered ports that do get clogged over time. Each port is metered to about .050 inch (a WD-40 straw fits).

I would think the V8 engines have something similar.

grege

So the idea is that a vacuum hose with a small amount of suck is connected to keep the cams a little below atmospheric pressure and prevent engine vapour getting out into other systems like the distributors?

mahunt

A vacuum hose with full intake manifold vacuum drawing through a tiny metered port in the valve cover that keeps the entire engine crankcase somewhat below atmospheric pressure.
Hopefully, the PCV system is able to handle all the combustion blow-by that gets past the rings.

John Coin

PM sent for the fix I would have posted it but is from a different mercedes fourm.

mahunt

It's OK if you link over to BW.

John Coin

https://www.benzworld.org/threads/co...#post-18056153