Fanman12

Hi, I recently had a problem with a bad judder in reverse gear so decided to check fluid levels and found milky pink fluid.
I presume water contamination but where will it be from?
the new radiator was fitted end of 2022, I was told it was a genuine Porsche unit which it appears to be.
there does not seem to be any connection between this and the cooler or am I missing something?
are there any other possibilities?
car is a 1991 S4

thank you for any advice given.

Mrmerlin

look on the back of the radiator tank on the right hand side,
just below the top hose inlet ,
you should see two lines connected to the tank,
these are the trans cooler lines,
based on your description the right hand cooler inside the tank has failed.
NOTE is it possible that the transmission was submerged in water or power washed?
you will need to flush the trans out ,
and replace the trans cooler,
a good shop could remove the side tank and swap in a good cooler.

Fanman12

Thank you so much for your quick and knowledgeable reply, I can see the connection now.
the radiator was new when fitted by a “specialist “ last October, should it have failed so quickly?
My coolant level has not changed and is still green so hopefully only a slight leak!

FredR

The pressure in the ATF cooler is very low as in enough to drive the ATF back into the transmission sump. The engine coolant system is pressurised at up to 15 psig depending on the expansion tank level plus an element of pressure associated with driving the coolant round the system by the water pump. When the engine stops the cooling system remains pressurised until it cools down thus unlikely a leak path will develop back into the coolant. Different with the engine oil system that is a higher pressure than the cooling system when the engine is operating.

Once the radiator has been removed you can have the ATF cooler pressure tested for leaks. How one flushes the tranny is somewhat more puzzling. Short of filling with fresh ATF, running it for a short while and then changing it again I cannot think of any other way. For a relatively new stock radiator unit at the prices charged for these things to fail like this is disgraceful- maybe you can take it up with Porsche if this proves to be the problem.

As Stan says if someone has something truly silly it is possible for waater to get into the tranny via the breather connection on top of the body- thus why driving through standing water is not a good idea should the breather connection get flooded.

ZEUS+

This is a definite indication of atf cooler failure. I have seen this numerous times in various makes and models. Do not start vehicle, run engine or drive. The ethylene glycol in coolant destroys the clutches in an automatic transmission. Ethylene glycol can dissolve the adhesive that bonds the clutch material to the disc. Radiator or cooler replacement, cooling lines flushed, drain torque converter, transmission service with system flush until fluid is no longer contaminated. Hopefully no damage was done.

NoVector

100% agree. My '84 had a leaking cooler and that's exactly how the fluid in my overflow tank looked.

For the OP, you can rig your own line flusher with one of those cheap weed spray jugs: