Cool weather + 0w40 oil = rear main seal leak?
 

Okay folks, I'm about ready to cry....and that's not pretty! :D About a week ago I bought an '01 SLK320 with 68K miles. No leaks anywhere -- of this I'm sure -- haven't seen a drop of anything in the week I've owned it. The selling dealer (a Porsche dealer) did an oil change recently -- pretty sure it's Mobil 1 0w40.

Last night, we got one of our rare cold snaps. About 32F/0C -- yes, that's what passes for "cold" down here in south Texas. Anyhow, this afternoon I back the car up the driveway...and what do I see but a good-sized oil spot! About where the rear main seal would be.

So, what's up here? Is it the cool weather? And yes, this is about as cold as it gets down here, so I can probably live with it if it only happens on cold nights. After all, I just bought the car so I'm feeling a little financial pain right now.

Words of wisdom? Suggestions?

Before you jump to conclusions, I would check their work first. Did they change the drain plug gasket? Is the drain plug tight? What about the oil filter? Take a look.

I really don't think 32f is cold enough to affect anything on your car, if anything the fluid gets thicker in cold weather. I would take it back to the dealer and let him know, you must of gotten some type of warranty the the car, you would hope.;)

Is it engine os gearbox?

Gearbox has a rubber wire grommet on front that develops a leak. Engine oil grade is correct.

Bazzle

98SLK230

True, but rear main seals become less pliable. However I agree with 32f not being cold enough to facilitate large dimensional changes. A motor with 68k is not likely to be a candidate for hard seals. If you believe the oil to be the problem, remove the synthetic, save it, and replace with organic. If a "hole" exists, synthetic WILL find it.

Good question. The fluid is not red, like I would've expected the ATF to be. So unless Mercedes ATF is colored similarly to oil, I'm assuming it's oil.

I bought the car "as is" but I'll let the dealer know about it. We'll see what they do. However, I also bought the car cheaply enough that even adding in a repair like this still keeps me below "private party" selling value!

You could also drive the car around for awhile, then pop it up on someone's lift, and take a look around. The type of leak you're speaking of, should not be hard to find. Do this soon, before oil is blown back over everything, possibly obscuring the true source.

I gave it some thought...and I'm pretty sure I'll at least be able to get the Porsche dealer to put it on a lift and see what's leaking. I can make better choices on what to do once I have a firm diagnosis...

UPDATE: Despite the freezing Texas temps (31F/-1C...woof!), I took a look under the car. There is definitely wetness around the tranny pan, but nothing below the torque converter/rear of engine.

So hopefully, this is merely the seal where the wires go into the tranny... :D