Coolant tank question
 

Leaking coolant tank and after trying poor fitting tanks off and on I managed to break the thermostat where the tank mounts?

Critical to have this thermostat in place or can I get by without until I can find a replacement. Nothing more than grocery trips planned.

Thanks.


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AFAIK that is the transmission thermostat so I don't think there should be a problem not having it in place (unless maybe there is a chance of coolant mixing with trans fluid??) I have never had that apart so just am educated guess on my part so if someone else knows more they should chime in. ;)

Yes, that thermostat regulates flow of coolant to the ATF cooler, which is the thing attached to the radiator that looks like a bunch of aluminum plates stacked together.

No chance that removing it would allow mixing of ATF and coolant.

I agree that it would probably be OK for short trips at least.

I don't know how that thermostat is supposed to control ATF temp = open when cold, to allow faster warmup of ATF? Open when hot to keep ATF from getting too hot? But then when is it closed??? :dunno: Can't imagine it is complex enough to be not just monotonically opening. Very curious myself, so if anyone knows ...

Here's a pic of the M54 cooling system in case that helps.
Attachment 82832

Oldskewel, that schematic is fantastic. Where did you find it, and is there one for the 4.4/4.6 motored x5s?

Not sure where I got it, but just now I used the google machine to search for "bmw m54 cooling system" and that was one of the first things it found.

Usually I find that great schematics like this make things crystal clear and logical. But some times, like this, the system may be so complex that it takes a bit more before things make sense.

Not even updating my search, but following some nice pics, I found
https://www.bimmerworld.com/About-Us...g-System-Tech/

which included this pic, which I have no idea whether it is the sort of thing you are looking for:
Attachment 82833

I ran mine without the trans t-stat for about two weeks while I waited for a replacement. Mine was broken when I pulled the tank. I had not issues.