car getting warm only when in traffic

[Blacke30vert]

so i have a 91 325i and i just flushed the cooling system and put in new coolant, bled the system with the bleeder screw and drove around for about 20mins in 80+ degree weather and happily my temp gauge sat on the middle line finally. when i stopped at a light for about 2mins the needle started to rise just slightly over that line but when i started driving again it dropped below the middle line then went back to the middle.

does anyone know why this would happen? for the past year I've had to drive with the defroster on even after i changed the thermostat, drove around today with vac off with no issues other than the stop light. fan isn't loose when i wiggle it and I'm not leaking coolant from anywhere.

[87-325ic]

fan clutch?

[e30onBBSs]

My money is on a decent but not full bleed. But if it fluctuates just barely it's no problem and you shouldn't worry about it.

If it never did that before and you are super worried, re bleed imo. Don't replace any parts until you are sure it's bled 100% then start the diag if need be. Pour coolant into upper rad hose re install and squeeze, repeat

[dnguyen1963]

I always drill a small hole in the upper part of the t-stat to help remove the last stubborn air bubble that can cause this problem.

[ttrousdell]

would it keep creeping up if you sat at the light longer? The needle going slightly above middle is still well within safe range. Id keep an eye on it but not something I would be too concerned about. Does the heater work while the car is at speed?

[jlevie]

Try the rolled up newspaper test on the fan when the engine is normal operating temperature. You may have a weak fan clutch.

[willworkfore30s]

Bleed it again with the front of the car elevated. I bet you've still got some air in there

[TobyB]

...and I'm in for not quite enough fan...

but I've had a marginal (fulla crap) radiator do this, too-
there's so much more airflow at speed, versus a rather
weenie little engine fan at idle....

t

[Blacke30vert]

would it keep creeping up if you sat at the light longer? The needle going slightly above middle is still well within safe range. Id keep an eye on it but not something I would be too concerned about. Does the heater work while the car is at speed?

It'll go maybe an 1/8 to 1/4 inch past middle if I sit for like 5 minutes to 10minutes. And yes the heater works while driving, I used to have to drive around with the defroster on to keep it from overheating.

[Blacke30vert]

Try the rolled up newspaper test on the fan when the engine is normal operating temperature. You may have a weak fan clutch.

I'll try the news paper when I get my fuel pump that went out today fixed lol

[Yeltsew7]

I'm having this exact same problem. The car stays cool when I'm moving, but as soon as I stop, it starts getting hot. When I get stuck in traffic, or even if a light is especially long, I'll have to shut my car off to keep from overheating.
I tried the newspaper in fan thing and it just cut up the newspaper, and the fan is impossible to move by hand if the car is off and hot.

I'm going to try to bleed the system again some time this week, but it'd be hard to keep it idling if it keeps overheating.