M54 thermostat replacement

x-driver

x-driver

Active member
 Slovenia
Yesterday during a trip I suddenly noticed that engine temperature had dropped.
I already checked for part number and found out at Hubauer and Leebmann that the part is unavailable.
If I can't get an OE part, what brand should I choose?

Should I also replace the water pump? What brand to go with here?
The car has 145k km (90k mls).
 
If you are doing one I’d do the other while you are there

Don’t buy a plastic impeller pump go metal only
 
The temp gauge can also drop because you have lost all your coolant. Check that first.
 
As I had to drive home and I was far away, I could monitor the temp gauge behaviour. It would rise uphill and with slow driving. And it would drop downhill and while driving fast.
I'd expect the temperature to rise if losing coolant, air pockets to appear...
I looked under the bonnet and there was no coolant spill visible. Also no strange smell or smoke from exhaust.
 
bigwinn said:
If you are doing one I’d do the other while you are there

Don’t buy a plastic impeller pump go metal only
Click to expand...

OE water pump has a plastic one if I remember right. Is it not worth buying then?
There is always a risk for leaking or early failing with aftermarket. Which aftermarket is safe to buy?
 
My symptom is only movement of the temp gauge between halfway between cold and working temperature position and vertical position (working temp). No overheating.
I didn't notice any temp changes through air vents, but I wasn't heating the interior anyway, so maybe there would be a change but I didn't notice.
 
Temperature going up when the engine is working harder (going up hill) and dropping when doing little (coasting down hill) or getting big air flow is classic thermostat stuck open.
 
So, an OE thermostat is unavailable, meaning aftermarket is the only choice.

Which is better from your experience, Mahle-behr or Wahler?
 
Behr was very probably OE. Wahler seems to be a big name in thermostats - I'm pretty sure that's what i bought when I did my water pump and stat about 3 years ago (N52, FWIW) and all good so far

These days choice of parts is very limited due to the age of the engine. Almost all companies are supplying Chinese parts but are hopefully paying for the good versions over the ones that end up as no-name eBay specials. I recently bought a few M57 bits and noticed that there's not the choice there was just a few years ago.
 
Hmmm... I askes the same question on slovenian BMW forum. 2 users stated they had issues with mahle-behr thermostat (one said it lasted 2 months, the other one replaced 3 in 3 years). One also recommended Wahler.

I think I'll give Wahler the first try :unsure:
 
x-driver said:
Hmmm... I askes the same question on slovenian BMW forum. 2 users stated they had issues with mahle-behr thermostat (one said it lasted 2 months, the other one replaced 3 in 3 years). One also recommended Wahler.

I think I'll give Wahler the first try :unsure:
Click to expand...
Ah well, everyone has different experiences. No doubt now you have just jinxed the one on my car. :rofl:
 
Funny thing though, for last 2 days it seems the thermostat works back again. Is this normal behaviour for when it's going out?
 
Possibly it had stuck open and has released itself again. You could see if it stays working but, if it's original, it's worth changing as thermostats get lazy and open early as they age.
 
A new one is on its way (y) I will also replace the water pump and hoses, both OE, hoping for them to work for ages 🙏
 
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