Heat problem

[GarrettM]

Driving my car, all warmed up, if I let the revs drop below 1500 or I'm sitting a stop sign/light, the heat considerable cools down. I think it even blows less. But when I am above 1500RPM, moving or stopped, it his on full blast. I checked the rad, and reservior (sp) and my blower works 100%. I am out of ideas at this point. Water pump?

[DaveSmed]

When was the last time it had a water pump installed?

[GarrettM]

Last time was probably at the factory.

[DaveSmed]

Sounds like insufficient flow. Could be crud build up in the core, valve, or lines, or maybe your waterpump isn't pumping like it used to.

[craig4ie]

sounds like something's clogged (flush system), there's bubble in the system (bleed system, might as well flush while you're at it), or you need a waterpump...

[BrewCity11]

Bumping this cause it's exactly what I'm experiencing.

Just did a heater core, valve, and thermostat swap on my car. Filled coolant, and bled it as well. At least I think i've bled it enough.

So yeah, same deal. Driving (above 1500 rpm) it's fine, but at idle it goes cold. I can feel the heater core, and it's hot as hell. Actually, almost too hot. So i know the coolant is flowing well. This rules out the core, valve, water pump.

Only two things I can think of are the temp control knob adjustment (which is in the Bentley), and it needs to be bled more. This weekend i'll bleed it on an incline, so that should help.

I'll post results here in case others would like a solution.

[1990m3]

air bubble -- run the system with the heat blasting and the reservoir cap off. It's a self bleeding system for the most part, should be pretty easy, but might take a while for the bubble to work its way out

[KenC]

air bubble -- run the system with the heat blasting and the reservoir cap off. It's a self bleeding system for the most part, should be pretty easy, but might take a while for the bubble to work its way out

word. give it some redline revs to blast the bubble through.

[DCColegrove]

Check and see if you don't have the heater hoses on backwards... Fit's your symptom to a tee.

The one off the back of the head (out) goes on the upper tube, the one that runs under the manifold (inlet) goes on the bottom...

Messed with the old guys a lot at BMW when the aux thermostat/bypass was retrofit on the e30s because it's the opposite from the older chassis.

[BrewCity11]

Roger that everyone. Thanks. I'll double check the pipes.

And re: the bleeder screw. When I was bleeding it, alot of coolant was coming out, along with all the bubbles. Is that normal? I was just expecting the trapped air to vent, but lost alot of coolant at the same time. Oh well, maybe some of the rats in the alley will suck on it.

[Money$hit]

I just had the same problem. Bled it and it pretty much went away.

[BrewCity11]

Bumping this cause it's exactly what I'm experiencing.

Just did a heater core, valve, and thermostat swap on my car. Filled coolant, and bled it as well. At least I think i've bled it enough.

So yeah, same deal. Driving (above 1500 rpm) it's fine, but at idle it goes cold. I can feel the heater core, and it's hot as hell. Actually, almost too hot. So i know the coolant is flowing well. This rules out the core, valve, water pump.

Only two things I can think of are the temp control knob adjustment (which is in the Bentley), and it needs to be bled more. This weekend i'll bleed it on an incline, so that should help.

I'll post results here in case others would like a solution.

Bled it again the other day, with the front jacked up. Ran it for 15-20 minutes, bled it from the bleed screw, revved it, all that.

Still no heat. Going to try the temp control knob adjustment. Maybe the flap isn't opening all the way for the heater core.