Pufftrees

Hi guys,

I've had a small oil leak in my engine for some time now. During standard service I had asked them to find where it's coming from and it was such a small leak they couldn't. During my most recent A service they discovered the leak is coming from between the transmission and engine.

I have a warranty on the car but it works like this. They will have to drop the transmission (5-600 bucks) in order to diagnose the problem. If the problem is something my warranty covers (like rear main seal) then they pay for everything. If the problem is something they don't cover then I have to pay for the tranny drop and everything.

So my main question is... what else could be causing the leak between motor and transmission. I would like to determine as many possibilities as possible so I can see what the warranty covers, and make an educated decision on the risk of having the part being covered.

Thanks!

Glyn M Ruck

It can only be the rear engine seal or the front transmission/TC seal if you are sure it's from inside the bell housing.

You need to make sure it is not the camshaft bore seals on the back of the engine or the transmission cooler line banjo bolts or electrohydraulic bush on the transmission assuming you have a 722.6 5 speed transmission.

Klinh

Can you tell which seals is bad base on the fluid color?

Pufftrees

Thank you for a detailed answer, I will take this information and talk with my warranty company and my mechanic.

I have the 7 speed transmission, 722.9-7g, does this introduce new things to look out for?

Glyn M Ruck

No - The 7G has no electrohydraulic bush because the TCU is built in so it eliminates that. Also does not use banjo fittings on the transmission cooler pipes but a nipple & clamp with bolt arrangement.

Good luck!

Glyn M Ruck

Yes if the fluids are fresh. On US cars the transmission fluid is red & the engine oil is straw coloured.

If the fluids have degraded to dark brown they look alike. Only the transmission fluid is lower viscosity.

Rudeney

One way to tell the fluids apart is by smell. The engine oil will smell metallic or hot/burned, and well, greasy like engine oil. The transmission fluid will smell "fishy".

alx

The proper way is to have them put dye in engine oil and check in few days with uv (black) light. If they see the dye as mentioned it is your rear main seal- very common. If not- it is the tranny.

Klinh

That's what i did on the Clk55 and Slk55 and reported the main rear seal leaked to the dealer. It got fixed under aftermarket warranty.

Glyn M Ruck

Well - there are many ways.

Primary colour of fluid.
UV indicator dye is a good one.
An oil industry person such as myself would pick it up on smell.
A quick IR scan would tell you.
A viscosity check will tell you.

Pufftrees

Love this forum

Well my mechanic got back to me. He explained that it is oil leaking and not transmission fluid. Here is his response to my initial questions:

"So this is a pic of the inside the bell housing area and the larger circle that you see is where the transmission connects to the back side of the engine and nothing is exposed until you drop the transmission out of the vehicle.

Two possible places for the leak:

The smaller circle is where the rear main seal is (behind the flywheel)
The line that you see that goes across is the where the upper oil pan gasket is.


The camshaft seals that you are referring to are way up top on top that is not a concern we would see them drip down (common and easy fix)
The transmission cooler lines you can see hanging in mid air and are not a concern and would leak trans fluid we are leaking oil.
The TC seal you are referring to is is an acronym for Torque Converter and this would leak trans fluid we are leaking oil.



The third thing that could be leaking is the rear main seal plate the holds the seal which gets replaced during the repair anyways that also cannot be seen without transmission removal."

Now I need to dig around my warranty contract.

alx

if you have a powertrain warranty you should be set. anything that is bathed in any kind of oil is part of the powertrain

Klinh

For home mechanic, the dye is the best method in term of sorting out the leaks.

Glyn M Ruck

Is that a picture of your car? Then you have a 722.6 5 speed transmission. I can see by the cooler pipe banjo & electrohydraulic bush hanging there. It's a CLK 500 - they never had the 7 speed. Only cars with M273 engine.

It will likely be the crank seal behind the flex plate. experience tells me that if the sump interface with the block is leaking it will leak outside the bell housing area as well.

Good luck!

Glyn M Ruck

Yes it probably is. The statement was that the "proper" way ____

I don't bite that.

Glyn M Ruck

Here is the seal installation procedure. A slight fiddle that needs to be done carefully.

BTW - we have it in the Wiki.

Pufftrees

Thanks Glyn! Sorry for the confusion, but that is a picture he found online to help illustrate my issue (since we haven't dropped my tranny yet). But overall I think I feel comfortable with the repair now.