About an hour after I drove my car yesterday, I noticed a huge pool of auto transmission fluid on the garage floor. I quick look revealed that it is from the back near or at the reservor and the reservor is empty. The car never leaked at all before this, not even a drop. It also did not leak while I was driving, no signs of oil
blown anywere else on the car? It was not leaking immediately after I have driven it, must have happened after I parked the car. Any ideas? I did not fill the oil recently, so it is probably not as a result of overfilling. I planned to take it in to have the aircon worked on this Wednesday, I guess I should not drive it? (10 miles)
Sias
89 S4 Auto

 

mastertech@mastertechtrans.com

Steve is the man!

 

Sias, lekker om van jou te hoor man .... the reservoir attaches to the trans with a plastic donut cap-like thing to make a firm connection to the tube that leads to the trans IIRC. So that is likely leaking?

 

Sounds like a split pan gasket. The bottom of the reservoir is even with the pan gasket, so you probably can't add any fluids with it in that state.

You should not drive the car with the level that low.

 

MB changed the gasket in ...wait for it........94!!! Porsche still sell the superseded gasket!!! Look for posts in the lasy couple of months by 'Tails'. I have a 110kb pdf of his spelling out this problem - relevant IF this is your problem- give me an email addr and I can send it you . The gasket splits at one of the centre side bolts. MB changed the part no from 126 271 10 80 to 126 271 11 80, on "administrative message 27a94091". If you buy a Porsche kit, check the gasket before accepting it, or just go to an MB dealer....In Tails case a brand new gasket failed 220km/135mi from installation.
jp 83 Euro S AT (3spd) 50k

 

Use an aftermarket pan gasket. Costs less, works great.

 

Thanks for all the input. I guess it is good news bad news! The pan gasket wasn't the problem, In fact, I could not find the leak? The car is at a local Porsche repair shop for some air-conditioner work and the owner, who is an ex dealership person trained on 928's, could not find the leak either. The oil level is set correctly as per the handbook(engine running etc) It did not leak a drop since? I drove the car to the repair shop and they test drove the car as well. While I am very happy that everything is fine, I still wonder what caused the problem?

 

Sias do you suppose it could have been overheated fluid? How's flow through the cooler at the radiator? Or, it is very normal to lose some (though not that much) from letting her sit a long time ...

 

Sias,

You need to check the level with the auto transmission at cold and then again at operating temperature, that is, after the car has reached fully operating temperature.

Cold check.
With the car on a flat surface the level should be checked with the engine running at idle, hand brake on and the transmission in "n" . Let the engine run at idle speed for 1 to 2 minutes before checking to allow the torque converter to fill and the level should be level with the cold mark (68 to 86 degrees F).

Hot Check.
With the transmission at operating temperature (176 degrees F) flat surface, hand brake on the level should be between the two marks on the reservoir(Hot max and hot min).

Check your owners manual for the method of ATF level check for your car as various types of reservoirs fitted to various models.

What may have happened is that your transmission may have been overfilled, the ATF may have been overheated, foamed and spilled over through the vent when you stopped.

WSM 38-23 states:

If ATF is too low, oil pump will draw in air. which can be heard. ATF will foam and cause incorrect readings when checking ATF level. Stop engine until ATF foam dissappears (approximately 2 minutes). Add ATF and recheck ATF level.

Excessive ATF must be drained or drawn off, since otherwise transmission components would splash excessively and raise the temperature too much, until finally foamed oil is forced out through vent. This condition could damaged transmission on a longterm basis.

Tails 1990 928S4 Auto

 

Thank you Tails. Very good info

 

Tails,

You need to run the tranny through the gears with the parking brake on or you will get a false "full" reading.

With the E-brake on, put the shifter into each gear for about 5 seconds, put it back in Park, and then check the reservoir level.

 

Hi there is a chance that the one of your trans oil lines has decided to give up the ghost I would look at both of them if either one is wet then replace both of them, they will be hard to see as they are both above the heat shields for the exhaust and run next to the torque tube, this is based on the fact that you had a puddle and the pan gasket is good and so is the resivour and cap

 

Thanks for everyone's input. I checked the oil level again over the weekend as described in this post and everything was fine. Everything was dry, no sign of a leak and the level was good, hot and cold check.
The whole week everything was fine. I did not drive the car Wednesday and Thursday. This morning as I pulled out, a nice pool of transmission oil again! I drove it straight to the Porsche repair shop that looked at it last time. I think it is pushing oil out at the reservor cap? But only after it sits for a while?
Anyway, I thought the problem was solved, but it obviously is not?
Any ideas welcome...
Sias
89 S4 Auto

 

I hope the tranny is not being presurised by the cooling system. Any sign of strawberry milkshake. Is the oil level in the reservoir still at recomended level after it has been leaking onto the floor?