Where is the transmission overflow?

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It is the black plastic cap on the top back of the tranny.

Thanks, is it this black plastic cap as indicated by red arrow?

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No, the back of the tranny on the other side.

It is this one

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

That is it.

I may be wrong, but I think its more to the left, towards the driveshaft end. Opposite side on photo, black round cap.

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

Nightmare.

Are you sure the brake piston cover above the red line you drew isn't leaking?

It might sound a bit daft but may be it is time to tape toilet paper to your car and see where the stains start to come through.

You'll look a bit silly - like you've cut yourself shaving - but hey it does work.

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

I degreased the trans a few times & once I see ATF on my garage floor, I jacked up the car & used paper towels to feel around (above the gasket) to see if the leak is from above....BUT still no luck.

Your toilet paper idea is very good, I'll give that a try. I'll degrease the trans once again & stuff toilet up above the gasket & just let the car sit over night...just to confirm if it's from above or the leak is actually from the gasket.

I had a stubborn leak issue on my car that turned out to be a leaking vacuum modulator... the green plastic item that is connected to the engine vacuum. The O ring on it was rotton.

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My first Mercedes Benz. 4/6/07.

1984 190E (201 024) 2.3L four.

I replaced my modulator last year. It was leaking into the intake manifold due to ruptured diaphragm.