Underside coated w/engine oil! - PeachParts Mercedes-Benz Forum

cewyattjr · #1 10-20-2007, 08:59 PM

My 300D is my daily driver, probably put on 60 - 70 miles a day. I've had an oil leak for some time, it seems to come down, right behind the oil pan, and leaves a half-dollar to silver-dollar sized stain whenever I park for the day.

I'm guessing it may be the seal between the transmission and the engine. Likely more than one leak. The valve cover gasket was recently replaced, so probably not the culprit.

Anyway, today, I got under the car and saw that WOW, much of the underbelly is pretty much coated with oily gunk. Even much of the exhaust. I guess that all helps protect from corrosion.

Though not a rocket scientist, I'm assuming this is an effect of driving with an oil leak over time.

My oil consumption doesn't seem too bad. Maybe a quart every 3k miles. So other than the mess on my asphalt driveway, how urgent is it to fix? If it is the main seal, I'm assuming $$ expensive labor.

Thanks,

Chuck

lietuviai · #2 10-20-2007, 09:29 PM

Your assumption is correct. Most of the labor is involved in R&R the transmission. If you're only adding a quart every 3K miles, I wouldn't worry about it. I'm sure most of that quart is consumed by the engine and not leaked out. Have the bottom steam cleaned and then be on the lookout for your leak. Most of your mess could very well be what's left over from the leaky valve cover and not the rear main.

tarbe · #3 10-20-2007, 11:12 PM

We call that the automated underbody corrosion control system. That was a port installed option for several years.

Amazing how the wind spreads that oil all over. But a little bit goes a long way, and it is almost always much less oil than we think it is by just looking at the mess (under the car or on the driveway).

You could also think of it as your continuous oil change system.

pawoSD · #4 10-21-2007, 01:47 AM

Quote:

Originally Posted by tarbe

We call that the automated underbody corrosion control system. That was a port installed option for several years.

Amazing how the wind spreads that oil all over. But a little bit goes a long way, and it is almost always much less oil than we think it is by just looking at the mess (under the car or on the driveway).

You could also think of it as your continuous oil change system.

I agree, thats simply the engine doing its part to protect the chassis that carries it from rust!

I can proudly say mine also coats the underside of the car with oil, and I have no rust there, in Michigan!

It also makes you have to add fresh oil to the engine, another good thing.

kerry · #5 10-21-2007, 11:18 AM

if the rear main seal has to be replaced, the crankshaft has to be dropped in addition to R&R of transmission. However, I wouldn't jump to the conclusion that it's the rear main. The oil filter housing to block seal is notorious for leaking and it tends to drop oil in the same vicinity as would a rear main. Same with the valve cover gasket.
Take it to the car wash and bring along your ramps. Spray off topside and underside and keep a close eye on it afterwards to locate the leak.

Stevo · #6 10-21-2007, 11:40 AM

I would make sure it isn't your oil cooler hoses, that could turn serious fast

Take it to the car wash and "de grease", or not

Gil · #7 10-21-2007, 02:11 PM

You might want to have a look at your vapor hose where it connects to the valve cover. I replaced the little elbow piece, as well as the gasket for the oil filler cap. Did an oil cooler hose also. I still have an oil spot under the car, but at least it's a lot smaller than before.

cewyattjr · #8 10-21-2007, 02:16 PM

Thanks all for great suggestions! I'll try the car wash with my ramps. Glad we own our driveway rather than rent.

junqueyardjim · #9 10-21-2007, 03:04 PM

I have one that is less then a year old and I know that is where my leak is and I can't seem to stop it. Remember 11 ft lbs torque in an "x" style. I am going to pull mine off this week and really try to get to the bottom of it. My driveway is the pits and my wife isn't happy.

toomany MBZ · #10 10-21-2007, 03:26 PM

Make sure the gasket did not dislodge when reinstalling, can be tricky. Some folks will put a coating of grease on the bottom of the cover, then the gasket to hold in place. If you pull it completely off, make sure there are no cracks around the bolt holes, I had to replace one because of that.

charmalu · #11 10-21-2007, 05:28 PM

These cars are like Harleys, just marking their territory.

I always had a problem with the oil filter gasket, changed it twice and replaced the oil filter housing thinking maybe it was tweeked.

hada leak at the back of the head. made sure the valve cover was was tight. even cleaned off the surface of the head with alcohol, or laquer thinner. also cleaned off the valve cover and the bottom of the gasket to make sure I had a good tight seal. still had a leak.
I almost looked like I had a leak from the head gasket, or it could have been from the intake manifold gasket.

But that eng. is gone now, so we will see how the new one plays out.

When they leak on the asphalt, it`s just a seal coat

.

My Mom sure gets annoyed with the MB when just one little black drop gets on her snow white driveway. they drive Fords, I guess they never leak.

Charlie

cewyattjr · #12 10-21-2007, 05:36 PM

I was thinking the same thing about the seal coat.

I'm sure the neighbors aren't amused either, if it isn't the motor oil on the driveway, I had a loose fuel sender on my veg tank and managed to drip some WVO up and down the street.

Probably helps the asphalt as well, but it has the local dogs were licking the pavement!