G Man

My damn trans still leaks after I replaced the pan seal with the new MB part. I got an e-mail from Steve C the other day and he said look behind the neutural start switch at the reaction valve. I can find nothing with this name in my manual. This is a royal PITA since the exhaust and shroud have to come off in order to inspect and work on anything in this area. What really sucks is that the car has to be running in order for the leak to appear. It is rather loud with no mufflers hooked up. It actuallly looks like it may be leaking from the vac modulator area. I need figure out how to get a closer look. Maybe some inspection mirrors will help. Can someone tell me where in the pic the reaction valve is?

Podguy

You can do most stuff with the exhaust in place but the exhaust shrowd removed. The switch looks confusing at first glance, but is easy to deal with. The outer ring on the wiring harness twists about a quarter turn and then the cable pops off the switch. It is a good idea to clean these contacts while it is apart and squirt the swirch down with some DeOxIt. The shift cable pops off then the shift arm slides off after removing the bolt holding it on. Once off the switch is held in place with two bolts and then just slides off over the shift shaft. The switch has a small plastic piece that fits into the shift arm. Be careful with the plastic part because it can break. If it breaks you will have problems with the started lock out and lose your back up lights. I did this with the mufflers in place, but with things cold.

Around the shift shaft is a typical oil seal. It just pries off and slides over the shaft. Easily replacable.

It is much more common for the Mercedes mosulator valve to leak. I had this problem on several Mercedes transmissions. The mosulator is held in place with a metal half round clip that bolts to the side of the trans. If you look on the picture you posted you will see a bolt just in front of the trans switch. Remove this bolt and the clamp comes off. The modulator then just slides out. It is sealed with a $0.50 o-riing although I am sure Mercedes will charge you more.

The trans is a Mercedes 722.3 and all the parts from the Mercedes will fit the Porsche until you get into the differential.

You might look at the o-ring seal on the resevoir. The ring loosens up and fluid can leak there too.

Good luck.

Podguy

Sorry - two bolts on the modulator valve to remove the clamp.

Dan

borland

The trick to finding leaks is to clean and degrease the outside areas where you think the leak is coming from. Follow that with a water rinse. Yes, you need an inspection light and mirror.

After drying, inspect the areas for leaks, you should find everything oil/grease free.

Then take the car for a short trip. Reinspect with the light and inspection mirror. If you still don't see the leak, wait longer between trips. Eventually, you'll be able to tell if its a slow leak that develops with running the engine, or develops with the car just sitting.

As for the reaction valve, it's the one in the lower right photo with the arrow pointing to it, manual refers to it here as the "pressure unit B1". Photos don't show the plug/cover installed. On my 90'S4, the plug/cover is actually a temperature switch and electrical cable.

G Man

Thanks for the tips. I am going to degrease the area before I look for any more leaking. When the engine is running it leaks at the rate of one drip every five seconds. I'll put the exhaust back up without the shroud and see if I can work with it in place. If not it will come back out.

borland

That's quite a leak. So it's not likely leaks from static pressure (oil pan gasket, shift lever shaft seal).

I'd check the plugs for the pressure taps too; they are on the same side and shown in the above photos.

You also have the transmission cooler feed line which connects just above the B1 pressure unit.
That's the most likely pressure leaker if its the original hose.

Steve Cattaneo

Jim,

With the car safely off the ground in drive look for a leak or drip behind the neutral safety switch, that is were the B2 reaction valve lives. If the transmission only leaks running and not off, it’s not the pan gasket.