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Discussion Starter · #1 ·
Hey all!

So I have been running without heat since last fall (which made for an AWFUL winter!!). I have tried a few things, and so far not much luck.

I flushed the radiator, but since it was winter, and bitter cold out, I was not able to run the hose through it to get all the junk out.. This made no difference at all. I changed the thermostat, still no difference. The car has never had a single issue with overheating, or even running on the hot side. Since it is finally getting warm out, I decided to flush the radiator again, this time I ran the hose through it until it seemed to run clear, I also took the hoses off the heater core and forced water through it to check flow, I ran the hose through each side until water came from the other outlet and ran clear. After that I put a bottle of rad flush in there and filled it with water, let the car run (as per instructions on the bottle), and then flushed it again, and refilled it with 50/50. The heater still doesn't seem to be working right.. It gets a tiny bit warmer than it used to, and it doesn't take as long, but it doesn't stay warm.

The symptoms of the heater are that if I have the controls switched off and turn on the vents with heat temperature selected, it will blow hot briefly and then cool off. The higher the blower motor speed, the faster it cools off and begins to blow unheated air. If I am idling, it blows unheated air, but if I rev the engine up to 3-4 grand and hold it there, the air gets hot. When I drive, it fluctuates from lukewarm back to totally unheated as I drive (seems to be based on the RPMs, more heat during acceleration, less heat while just cruising).

I know it's not a plugged heater core or bad thermostat.. I'm wondering if anyone can give me some advice on what to check next... I feel like it seems like a water pump issue since the heat increases with RPM, but it doesn't make sense that I'm not running hot or overheating. My other thought was a blend door actuator or vacuum leak. I'd like to see what some of you guys think.

Thanks!
 

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Discussion Starter · #3 ·
It is a 2000, and I must say, I did not open the vent plug to refill, just filled the radiator, the degas tank, then ran it with the cap off and a funnel inside with some 50/50 on hand to top off whenever it went down. I have had no issues with overheating, but I will bleed the system tonight and see where that leaves me. Thanks for that heads up.


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Discussion Starter · #4 ·
Well I've attempted to bleed the system a few times, never seems low, still no overheating A/C works great, and engine temp stays exactly where it should. After driving, the heater blows warm when first turned on, then slowly cools to whatever outside temp is. If I keep the blower on the lowest setting, it stays a little warmer and for longer, but eventually it cools down...


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Questions.

When the heater does blow HOT, if you adjust the temperature setting (blend door) does it make a difference? Trying to determine if the blend door is moving when the temperature is adjusted.

Does the coolant system maintain and hold pressure?

When you attempted to bleed the cooling system, did any air come out of the bleeder? I would assume that it did on the 1st attempt. My question is about the 2nd and later attempts.
 

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Discussion Starter · #6 ·
The temperature control knob does make a difference, if it's on the cool side it's definitely cooler and on the warm side is definitely warmer until it loses its heat.

The coolant system seems to maintain pressure, how would I test this to be sure?

It definitely had some air the first time, in fact it seemed like the upper hose had mostly air in it, now the hose appears to be filled with coolant as it should be, and the coolant level in the bleeder valve stays up.


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If the temperature control does make a difference this says that the blend door is moving.

I suspect that you will find a bad water pump bearing. Take the belt off and inspect the water pump. How does it feel when turned by hand? Check for excessive up/down and in/out play. Any evidence of coolant weeping?
 
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