Heat issue

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Dec 18, 2020 | 04:20 PM

Mr. Rogers

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Heat issue

1998 Navigator. Changed thermostat because engine wasn’t warming up and heater not warming up. Now car is heating up ok but heater both front and back not heating up. Any ideas?

Last edited by Mr. Rogers; Dec 18, 2020 at 04:21 PM. Reason: More info

Dec 19, 2020 | 10:34 AM

alloro

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Are the heater hoses too hot to hold onto or are they just warm?

Dec 19, 2020 | 01:40 PM

Mr. Rogers

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Heater hose barely warm. Has both front and back h after. Both cold. I’m leaning towards a blockage but not sure.

Dec 21, 2020 | 09:16 AM

alloro

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Quote:

Originally Posted by Mr. Rogers

Heater hose barely warm. Has both front and back h after. Both cold. I’m leaning towards a blockage but not sure.

Yes check for a blockage or a bad water pump.

Jan 11, 2021 | 09:39 PM

bnorwood

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Quote:

Originally Posted by alloro

Yes check for a blockage or a bad water pump.

Wait - if the water pump were bad, wouldn't the engine be overheating??

I'm having a similar issue in that I have NO heat whatsoever, although the engine heats up to temperature just fine. I used to get a small amount of heat *if* I kept the blower on "lo". Now, nothing. I had assumed that the blend door had finally stuck all the way shut.

The heater hoses get hot; I have never attempted to measure a temperature difference between the two, but I assumed that if I wasn't getting airflow across the core (blend door stuck in the 'cold' position) I wouldn't see a temperature drop. Is that a bad assumption?

Thanks!!

Jan 12, 2021 | 10:19 AM

alloro

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Quote:

Originally Posted by bnorwood

Wait - if the water pump were bad, wouldn't the engine be overheating?

More likely in the summer than the winter. But that aside, the water pump by design pushes more coolant through the engine than the heater system, which is why when the coolant is low the heat will blow cold even though the engine isn't overheating.

Jan 12, 2021 | 05:04 PM

bnorwood

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From: Mechanicsville, VA

Totally agree with respect to *coolant level*....but the OP said "a bad water pump". In any season here in the "lower 48" I would expect an engine to overheat if the water pump failed.

Brad