Coolant tank question

[Oldmactech]

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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[80stech]

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.

[oldskewel]

Originally Posted by 80stech

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??? 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.

[Henn28]

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

[oldskewel]

Originally Posted by Henn28

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:

[Fifty150hs]

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.