In the past 2K miles I've noticed a black tar/oil like goo coming out of a half-moon hole at the top edge of the prechamber housing on #4 injector. It migrates into the prechamber/injector housing and down the side of the head to the intake manifold. I clean it off once a week only for it to return then build up like a lava flow. When it the engine cools off it hardens and I pick it out with needle nose.270K on the clock; timing chain, drive gear, head gasket all replaced@238K. Currently none of the others are leaking like this.
My old indy mechanic, who is now retired, did a temporary bypass on the EGR, with the EGR connected to the mixing valve unit via a hose, while the hoses from the vacuum pods are connected back to each other. I know this isn't the right way to do it but until I do the GSXR method of changing out the wastegate boost to bypass the computer, I'll leave it be unless this is known to cause problems. I mention all this because I don't know if this is a factor. Its been bypassed since I bought the car with 200k, and this problem has only surfaced in the past 2k miles.
I spoke to a mechanic at the local Mercedes stealership. He said this is most likely a result of incomplete combustion of diesel, with the by product, a tar-ish goo, working its way up slowly for the past 50 k miles and eventually leaking out. Basically he said there was nothing I could do except pull the prechamber and clean everything. I asked him if it could be a symptom of worse things to come, like a bad ring, but he didn't think it was.
Anybody else have this problem, or know if this combustion theory is correct? If it is combustion based, what can I do to fix the problem, or do I live with it?
03-25-2010, 01:13 PM
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