Normal temp gauge range

[blalor]

Morning, all. After replacing the engine in my '91 318is with another M42 (including the water pump and thermostat) it appears to be running a bit warm. The needle hovers between the 12 o' clock position and the next warmer mark. It seems to climb slightly higher when I'm cruising at around 80 and then drop a smidge when slowing down. I don't recall what it looked like before swapping engines, but this seems a bit high. I used the thermostat indicated by realoem.com, p/n 1153751158, which appears to be an 88 degree C thermostat. Is this gauge range normal for that t'stat? I'm thinking I should go slightly cooler.

Thanks,
Brian

[monty23psk]

Make sure it is bled very good. You might need to do it like 3 times.

[blalor]

I'll try bleeding again, but that's not really my question… :)

[blalor]

I'll try bleeding again, but that's not really my question… :)

[s_ribs]

In my experience, E30's never run past the middle mark when everything is dialed in. Typically the warmest the gauge indicates is ~one needle with to the left of the middle mark. Often the will run about halfway between 1/4 and 1/2.

On my M42, it always drops temp when coasting in gear - especially when going downhill. It never goes higher than a needle width shy of the middle mark.


Things to check/do:
-Make sure the system is bleed properly. This expansion tank style is more difficult to bleed properly. Once you learn the tricks they are easy but still a little more time consuming.
o Basic symptoms include inconsistent/weak heat through HVAC system
o Or, engine temp isn’t very consistent and changes a lot.

-How many miles since the last coolant change? How many miles on the motor? (In your case, it’s unknown with the engine replacement unless it’s a fresh rebuild.)
o Do a flush on the system, especially if the coolant change is overdue or mileage is higher.

-Check your fans
o Auxiliary fan/temp switch working?
o Fan clutch working?
o Do you have a fan shroud installed? It makes a far bigger impact when not moving than most think


Before replacing my water pump this past weekend I did a full flush on the system. Idled with it in the cooling system for 35-40 minutes per instructions and then ran water through until I was certain everything was out. Refill, bleed, etc. I never ran hot before but my temps fluctuated a bit. After doing this my temp has been very steady and doesn't move much. The only time it changes is when slowing down in gear and the temp drops.