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I had the same problem. The answer to your problem is simple. You have an air pocket in your cooling system. Simple fix - take the radiator cap off of the radiator, turn the vehicle on and let it run for 1hr to remove the air from the system. Also, make sure your overflow container is atleast at the minimum level. Answer If your certain you have all of the air out of the cooling system the blend door inside the heater box may be stuck open.

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โˆ™ 2009-02-06 04:16:24
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Q: Why would a 1989 Chevy Silverado 350 heater only put out luke warm air even after changing the thermostat and back flushing the heater core?
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Related Questions

How come your heater blows cold air in a 2000 silverado?

The heater might blow cold air in a 2000 Silverado because the thermostat is sticking and not changing from cold to heat. The thermostat is usually located in a hose that leads from the radiator to the motor.

Your truck does not produce heat its warm at first then cools down you already replaced the thermostat?

Try flushing heater core Try flushing heater core

Why no heat on 1990 silverado heater core I've changed control and thermostat.?

Have you flushed the heater core?

How do you change a heater core in a 1998 jimmy?

Before CHanging the Heater Core, have you tried flushing it? I have a 99' Jimmy and have to do this every year to get my heater to work.

Why does heater still not heat up on 2000 Chevy blazer after flushing and changing termasate?

Heater Airbound? Heater control cable not working? Heater core plugged?

Silverado heater blows cold air only?

possibly thermostat stuck in the open position?

Why wont the Heater on 2000 Chevrolet silverado get warm but not hot i have changed thermostat?

What temp. thermostat did you put in? Try a higher temp. one. or check to see if heater core is clogged

Why is my s10 blazer not heating?

could be a bad thermostat try replacing it answer try flushing out your heater core also

What would cause you to lose heat in your 1999 Chevy silverado if your thermostat and heater core are both good?

Your heater relay switch may be bad

Why won't my heater blow hot after a coolant flush and changing of the thermostat in a 2000 Taurus?

probably the heater core is clogged

2000 silverado heat wont work not thermostat not heater core not controls whats wrong?

try the bend door

What if your 2004 silverado temp gauge runs above normal in town and the heater blows cold but runs at normal temp on the freeway and the heater works fine What is the cause?


How do you know if your thermostat is shot?

If the engine is overheating, the thermostat is stuck closed. If the heater is not putting out enough hot air the thermostat is stuck open. Change the thermostat as a normal part of maintenance when changing coolant.

How do you fix a heater that is blowing cold air on 93 Buick Le Sabre?

start by changing the thermostat

What would cause a vehicle heater to blow warm air when blower on low but blow cold when blower turned up?

Poor coolant circulation from a plugged up heater core. Try flushing the heater core and replacing the thermostat.

Why is the heat only hot when press on the gas on the Infiniti G35X?

Could be low on coolant or the thermostat is stuck open.Could also try flushing the heater core.

After flushing coolant and replacing thermostat heater now throws out cold air on a 2000 Toyota celica?

Flushing sometimes frees up mineral deposits that then clog up your heater core. My mechanic told me to never flush a Toyota as the heater core was low in the engine. That is, only drain and fill when doing a coolant change to prevent dislodging the deposits.

Why would the coolant light come on and the heater blow cold air in a 1985 Cadillac Deville 4.1 even after you tried replacing the thermostat and flushing the radiator?

Heater core (radiator) needs to be cleaned or changed

2000 silverado 4.8L No heat thermostat replacement?

Try the thermostat, second see if the heater core is plugged up if that's not the problem see if the engine is even running hot enough

Why does a heater in a 1999 Chevrolet silverado blow cold air with thermostat on hot?

more than likely the coolant level is low otherwise check that the thermostat is functioning properly. if neither of those seem to be the prolem than you possibly have a blocked or bad heater core

What stops a car from heating up?

Normally this is caused by a thermostat that is stuck in the open position. Replace the thermostat. If you are only referring to the heater reaching the correct temperature it can be a bad thermostat or the heater core can be clogged . You can try back-flushing it to remove any clog but may end up having to replace the core which is always a time consuming job.

Why cant a 1999 ford expedition get heat after changing thermostat antifreeze water pump still no heat?

heater core....

Why does a 2001 Chrysler 300m has no heat after changing water pump and thermostat?

The heater core is bad that's why you do not have any heat

Heater blows cold air change thermostat warm air comes from right side cold air left side?

had a similar problem with dodge caravan, tried all sorts of thing like changing heater core, thermostat ,heater control valve and pulling radiator and flushing entire system turns out the the fins on the water pump were worn down and wouldn't pump the coolant didn't think it could have been pump as it was replaced not even a year ago hope this helps good luck

Where can one purchase a heater thermostat?

A heater thermostat controls the temperature of water in a heating system. A heater thermostat can be purchased from companies such as Hygiene Supplies Direct and Alibaba.