Mercedes-Benz Forum banner

Engine oil draining from intake manifold

2K views 3 replies 3 participants last post by  Savannahbenz 
#1 ·
Hey All, here is my short backstory. Rebuilt my '91 300 SEL Gas M103 engine both head/valve and block recently. Installed the timing chain tensioner incorrectly, fully extended which ate threw it's rail within 20 minutes of engine operation (lessons learned, eh? ). Before the timing chain snapped the engine ran like a sewing machine.. nice, quiet and smooth. Perfect.. well until you know.
So having bent 4 valves (that's another story) it required head to come back off. During re-install I tilted the intake manifold up on the front edge tip to pick it up and out ran which appeared to be old dirty crankcase oil out of the #1 pipe. It had the same type of viscosity of oil but naturally with a fuel odor. But unlike just fuel, that stain on the garage floor did not evaporate like gas would alone but remains like an oil stain. There was no evidence of blown rings, gaskets or any other reason for the presence of this fluid in the intake manifold I can think of. I'm praying its just the carbon buildup that's dissolved in the trace fuel that ran out but its slippery like engine oil.
Anyone have any experience with or ever seen this before?
Thanks,

Rick L.
 
#2 ·
Hi I just ran across your thread. Today I discovered the same stuff in the bottom on my intake plenum, (M103 in an 87 E class). My car has been having some running problems likely tied to vacuum leaks so I'm just replacing vacuum hoses and lines. When I pulled off the fuel distributor, I was amazed at how dirty the throttle plate was and then discovered all that goo when I opened the butterfly. My metering plate and crankcase to air cleaner breather tube are clean and dry so I don't think it is anything other than a mix of oil vapor, carbon and gas residue that has been collecting in the lowest spot in the intake system for 25 years and 240,000 miles. I'm going to clean the throttle plate and then just mityvac the residue out of the plenum, and hope for the best. I cant see any way for large amounts of oil to enter the intake without leaving telltale signs on the metering plate.
 
#3 ·
I've seen all the car at the junk yard are like that. Not really sure the purpose of that plenum design. I'm sure my parent 300se has just as much oil and the valve is just as dirty but it ran purefect and so I'm not worry about it. Though I did the Seafoam last week and it got even better.
 
#4 ·
I noticed that the rubber boot for the fuel distributor has a lot of residue in it as well. I'm changing my boot due to a loose connection at the idle intake hose. I'm pretty sure the residue is just a long term accumulation of breather vapor and gas. I'll clean it out just because I'm already down there, but I would not pull the FD just to clean out the crap. Seafom is probably a good idea.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top