Cooling system woes..... again...

[AtariMasta]

Still overheating.

Car only seems to overheat on the highway, when speed is constant. I can get the temp to go back down and stay back down by putting the heater at full-hot / fan on high.

Within the last year, replaced the thermostat, fan clutch and radiator.

Spent last week bleeding out air bubbles, and yet it's still overheating. Even went as far as raising the front-end 1ft above the back, quite a scene.

I'm questioning the water pump, although records with the car claim it was done about 3 years, 20K-miles ago. I still get good flow from what I can tell, maybe it isn't good enough? Maybe there's some blockage?

Opinions welcome.

Thx-
Luke

[kenika65]

maybe you are not overheating and your gauge is wrong

[BBY1104]

Bad temp sensor maybe sending a false reading? Or is it actually overheating in the engine bay, with steam and such?

[strad]

If you got any sealant in the bleed-through area on the therm housing, the system won't bleed properly.

Other thoughts are to check the water pump, check and see if oil in coolant/vice versa, verify temp with a temp gun (when it seems to be high of course).

[AtariMasta]

I have considered the sensor, its been fine for the past few days. It creeps up though like it is working properly.

No steam or signs of leakage that I can tell.

I bought a waterpump in the hopes I wouldnt have to install it..

-L

[AtariMasta]

Where is the coolant temp sensor? Is it the one on the head, infront of the intake manifold?

-Luke

[BBY1104]

I honestlydont know which one it is, I think it is connected to thermostat, which might also be bad

[AtariMasta]

Replaced thermostat, I cant find any sensor right around the housing. The Bentley I have refers to the previous 1.8L 4-cyl, the M40 but theres no love for the M42. Of which, the M40 i understand is like your M20 motors, having a sensor on the housing... IIRC

-Luke

[BBY1104]

The m42 will only be in a e36 book

[txleadfoot]

Last time I had an overheat, the plastic impeller on the water pump had disintegrated. Replaced with a new (metal impeller equipped) water pump and all is good.

[rallyegolf]

from what I understand is the metal impellers are the ones that carode and dissinagrate, so the plastic ones are better. If you have mineral free water, then the metal should be fine.

[E30nate]

the sensors are on the side of the head underneath the intake. the front one is for the ECu, the rear one is for the gauge. i think one is black and one is blue.