Again, still in the pursuit of finding the hose thats leaking I've discovered some interesting things in the cooling system of my 928. First of all, the ATF leak is coming from the front passenger side of the car and I have been told its the line that's right below the upper radiator hose.

What someone else told me in a previous thread is that if I have a line thats on the driver's side upper part of the radiator, than its a radiator used to cool oil...well now here's the big confusion part. Does my radiator cool 3 types of fluids!? ATF, coolant and oil??? pictures are below....

 

It is my understanding that the radiator for the Automatic Tranny sharks do cool the Rad Fluid - the tranny fluid and the oil. There is also an extra tranny cooler (Pre MY ?) - Someone please correct me if Im wrong.

Thanks!

 

Drewster what I don't get is why 928 Intl specifies my radiator as a 2-cooler radiator if auto cars cool all 3 fluids

BTW I added a PET diagram of the hose leaking. I hope that's the right one if thats leading to the leak.
Here's the link for my model, I think.

http://www.mailordercentral.com/928i...em=14&mitem=80

 

'2 cooler' means two EXTRA coolers, one in each side tank - ie tranny fluid and engine oil. Its not a count of the number of fluids being handled. Its assumed you know its mostly cooling engine coolant. Do you want to call a normal radiator (with No extra coolers) a zero cooler radiator when its doing 1 fluid?
jp 83 Euro S AT 48k

 

'Cuz the '2-coolers' are in the end tanks of the rad, specifically for ATF and engine oil: the primary function of cooling antifreeze mixture is just taken for granted.

 

so the 2-cooling means 3-cooling actually, including the radiator fluid. I feel really retarded now At least I can understand the cooling system on this car a little more. Next year my father turns full ownership over to me and my half becomes whole. The least I can do is study this car and do a better job at maintaining it since I will learn more about it.

Thank you very much you guys. For everything as usual.

 

Stig - rather than ordering new cooler lines - have your old ones rebuilt. There are shops out there that all they do is rebuild liquid lines. They take your old ends and install new hoses. I had this done on my 87924S when my a/c line was leaking. 300.00 vrs 35.00.

Also - thanks to everyone for the "inside" info on the cooling properties.

 

Well, I don't think that's quite the whole deal. Notice that the trans fluid goes through the hot side of the radiator. The oil cooler -- on mine at least -- goes through the cold tank on the radiator, implying that it is to be cooled. My understanding is that this configuration(which I've seen on many other cars) is intended to serve a dual purpose. I think you will find that the air-ATF heat exchanger is upstream of the water-ATF heat exchanger. If so, then I'll venture a guess that the one in the radiator was intended to warm up the trans fluid, especially after initial start-up in extreme cold conditions. This could be verified easily by mounting three thermocouples to the heat exchanger fittings and going for a drive. I imagine the one in the radiator would also help cool the ATF if the ATF were significantly hotter than the water temp, which might be the case in extreme high ambient temp or extreme driving conditions. Regardless, it's best to stick with the one in the radiator as a minimum, since there are a lot of benefits to getting the ATF warmed up quickly.

 

Generally engine coolant warms up quicker than engine oil or tranny oil, and stays at a more stable temp than the oils would otherwise, so intercooling them helps to stabilize the oil temps. Note that the engine oil lines have a thermostat to stop the oil going to the radiator cooler when the oil is cold at startup.
hth
jp 83 Euro S AT 48k

 

Good point jp, and I bet there is no thermostat on the ATF lines...

 

Thanks guys for all your help and the suggestion. Tomorrow I'll attempt to locate the leak with my buddy with the help of his rack at the shop he has.

 

toadally Dude!

 

toad-ally? Are you making fun of the car in his sig, expressing some sort of froggy 911 alliance, or what?

 

Dave I'm way too simple a creature to have thought any deeper than the original attempt to sound "OC"-ish

 

Andy,

The PET diagram is incorrect, in that it shows the short ATF hose connected to the transmission cooler (in front of the radiator) on the bottom connection. It's possible to install it there, but the service life will be reduced considerably due to the manufactured length which would stress the hose fitting near the radiator side.