So, as I'm sitting in the drive thru line with the heat blasting to try to ward off 14* cold, I realized that the air that had been hot 2 minutes ago was now freezing. I blipped the throttle and voila - warm air. Until it wasn't.
Basically, it seems that at idle, I'm not moving enough water thru the heater core to keep up with what the air is drawing away.
Thoughts? I'm a bit concerned that this is a sign that my water pump is on the way out. Any other possibilities?
What car? The first thing that comes to mind is the heater flow control valve that all these "modern" cars seem to have.
Clem
Water pump... or some kind of valve stuck half-way in the diverter doohickey that routes water thru the heater core so its only going that way when under real pressure?
Or - if its a BMW, roll the selector on the middle vent until the red dot is showing otherwise you are flowing some degree of cold outside air straight thru past the core.
ClemSparks wrote: What car? The first thing that comes to mind is the heater flow control valve that all these "modern" cars seem to have. Clem
2002 WRX. I don't think it has anything fancy. The temp control is a knob that feels like it's a cable control.
Low on water/coolant. Always happens when I open up the cooling system until I get the air bubble out and fill it back up. Also happens when I let it get low due to small leaks and neglect..........
SVTF wrote: Low on water/coolant. Always happens when I open up the cooling system until I get the air bubble out and fill it back up. Also happens when I let it get low due to small leaks and neglect..........
Hmm. Could be. I did replace the radiator about 8 months ago. Burped it a couple of times in the first day after replacing it, but never checked it again. That's a thought.
Exact same thing happened to me last week in my 02 WRX, the radiator was leaking and it was getting low on coolant.
I say air bound. I've had that happen a bunch before.
In reply to DILYSI Dave:
Low coolant level is what I'd look for first, or air pockets in cooling system.
Had a Lexus that did the same thing anytime it was a drop low on coolant.
Naw, its none of those. Your engine is too efficient at turning the burning gasoline into power and not wasted heat. 
You need something that gets 8 mpg then the heater will blow nuclear heat. 
RossD wrote: Naw, its none of those. Your engine is too efficient at turning the burning gasoline into power and not wasted heat.
Even better: an anti-lag program tune to make the car produce boost at idle! Lots of heat an no more sneaking up on pedestrians!
Poor flow through the core at low engine speed. Fluid level first, second make sure its no more than 50/50 af/water, then pull the heater hoses off, flush the core with water, fill it with CLR and go have lunch. Flush it again and be warm.
Trust me. I'm from Saskatchewan.
Poor flow through the core at low engine speed. Fluid level first, second make sure its no more than 50/50 af/water, then pull the heater hoses off, flush the core with water, fill it with CLR and go have lunch. Flush it again and be warm.
Trust me. I'm from Saskatchewan.
I had a Ford Explorer that wouldn't heat at all.
The next chance I got I took the heater hoses off the core. I then used a garden hose to reverse flush it. Basically I put the hose on the output end of the core and shoved water through it backwards. I then watched a bunch of rust, water, and anti-freeze coagulant flow out the other end. I refilled the rad and enjoyed roasty toasty heat.
Be sure to check the level in the tank up near the intake. The overflow tank on mine was full but the main tank was low which caused it to not heat at idle.
I also would suspect low coolant level first.
That was it. And it wasn't all that low. Between topping it off at the radiator cap and the coolant tank, I probably added less than a quart. But it now keeps me toasty at red lights, so that was it.
My 944 and GTI both do that if they're a little low. It's a good thing on the 944, because it has a very slow leak (that I finally found) and the weak heat at idle was like my warning light, only it would happen way before any light or gauge would tell me anything.
Easy, don't stop driving
definitely low coolant. Make sure to seriously bleed the system when you refill it. to be done right in freezing weather typically takes about 30 minutes or so.
a little tip for hard to bleed cars: Lift up the nose so the filling point is above the dashboard.
a lot of modern vehicles have their heater core higher than their fill point which makes them harder to bleed all the air out of.
A modest wood stove installed in the back seat area would surely be a superior source of heat.
check for a weaping radiator. It took me a year to finally discover the problem in my civic.
I'd still look into adding a big block of some kind... Why only be warm when you could be slow roasting a pig?
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