Anyone have experience with Mishimoto 70C "Racing Thermostat" for M54?

[1823alex]

Hey all, I was just browsing Mishimoto's site and it's lack of options for us E39 owners (especially the i6 owners) but did come across the M52, M54 and M56 thermostat that opens at 70C. I know lots of others on here have had success with the 88C conversion to keep temps low and prevent overheating & warping of the M54's aluminum heads. Has anyone used the 70C one from Mishimoto specifically or could give any reason why it would be better and or worse than the stock or 88C thermostat?

Also how would the electronics work with that?

Link to the product: https://www.mishimoto.com/bmw-m52-m5...hermostat.html

EDIT: Also to add I currently have the clutch fan deleted as it broke awhile back and I never decided to put it back in and haven't really had temp issues due to it lately.

[Mike WW]

I'm not above tweaking things or using non stock spec parts, but 70C is awfully low. Stock is what, 97C? Quick and dirty math says that's 50F cooler. The infamous buffered temp gauge may not show it, but that's pretty cold. I would expect MPG to suffer a bit. Not a ton, but a bit. I doubt it will set a check engine light, but it's not beyond the realm of possibility.

Many disagree, but I'm of the school of thought that a lower temp stat won't help on overheating, but a reread shows that's not a problem for you. It might make the plastic cooling system parts last longer and less likely to blow up radiators though. I wouldn't do it, but I doubt anything catastrophic will happen.

[mattmar1]

personally i wouldnt delete the clutched fan for any period of time (unless you replaced it with an electric), cuz you lose the aux fan as the backup, it becomes the primary. stuck in traffic on a hot day and the aux fails, youre done. kinda defeats any purpose of a lower temp thermostat.

[MotorMouth93]

I would go with the factory tstat or 88C tstat, 70C is extremely low.

[jicaino]

I have the 88°C and it's kind of on the low side (on both cars, the V8 and the I6). 70°C it's really really low, and in my opinion useless even for a racing car. 80°C would do fine for racing.

[1823alex]

Thanks for all the replies guys, definitely gonna stick with stock for now and maybe later on switch to the lower 88c one, but for now it's just fine. I was curious if anybody had experience with it, plus 70c is quite the drop from the 88c one.

[jicaino]

IIRC the stock one is 92°C which is already fine. I used the 88°C for the stupid reason that I got one for the 540i in 88°C from a diesel equivalent, so when I replaced the stat on the I6 I did the same, but it actually worked fine with the 92°C, operating at tops 95°C sitting in traffic. With the 88°C in the I6 I'm seeing the same operating temps range but worse mileage. In the V8 the operating temp range dropped back to "normal" (90/94°C) so it was an actually useful mod.