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I have a 2001 silverado 5.3l 4x4. My heater blows warm air sometimes and then blows cold air. My thermostat stays at a steady 200 degrees when warmed up. I filled my coolant and didn't have any leaks, does anyone know why I am not getting heat constantly?

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Sounds like air in the cooling system. Try taking radiator cap off and letting the vehicle run with heater on high. As bubbles come out add coolant. This may take 20 minutes to a half hour.

Posted on Nov 25, 2013

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Posted on Jan 02, 2017

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brainyass
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SOURCE: heater only blows warm air.

The hoses from your heater core should be very hot to the touch. Check the hoses going to the core from the water pump. It should be very hot. The return hose should also be very hot. Now check the hoses going to the core. If they are not the same temp, then your heater control valve is not working correctly or the vacuum is not working. At any rate, locate the vacuum line going to the heater valve. Remove the silver bar on the valve from the plastic plunger arm. You will have heat all the time now if it was only a vacuum problem. You can fix it later when it's warmer out. BTW a 200* thermostat will make your heater even hotter.

Posted on Nov 21, 2008

JMMARRERO59
  • 77 Answers

SOURCE: 1998 Dodge Durango no heat when using heater.

BLEND DOOR STUCK OR BROKEN. NEEDS TO REMOVE DASH AND HEATER/EVAP CORE BOS TO REPAIR REPLACE.

Posted on Jan 08, 2009

emissionwiz
  • 76846 Answers

SOURCE: heater blows cold air ac blows warm air

Your problem is the air temp control blend door actuator is defective and not controlling temp u set. to change/access this part the dash assembly must be removed from the car.

Posted on Mar 24, 2009

juncro
  • 467 Answers

SOURCE: Air conditioner blows alternate cold and warm air

check the freon level

Posted on Jul 16, 2009

  • 108 Answers

SOURCE: blowing cold air via the heater

Assuming that none of the Electrical/Electronic controls were disturbed when changing the Thermostat it seems to me that you have an "Air Lock" within the heater. One must purge all the air out of the cooling system as close to the highest point as possible after the system has been partially or fully drained. Most of the time one will find small BRASS Bleeder Valves located somewhere near the highest point. Open each one while the system is pressurized and let Air escape until some Coolant escapes. Sometimes it may be necessary to loosen a Heater Hose and bleed the air at that point. Remember that the system MUST BE PRESSURIZED to accomplish the Bleeding of Air. Many auto parts stores sell hand pumps with a pressure gauge for this purpose and leak testing. These pumps typically replace the Radiator Pressure Cap temporarily. The system does not have to be at normal operating temperature to bleed the air out. Once the Air has been bled you will have to refill the radiator to normal full and make sure that the Coolant Recovery Tank level is also brought up to recommended level. A quick check is to remove the Radiator Pressure Cap, Start the Engine, Rev the engine suddenly (A short Jab) and see if the coolant level falls rapidly in the radiator. If it does it is definitely an AIR LOCK situation.

Fastest Robe

Posted on Nov 19, 2009

Testimonial: "Thank you, I'll do the quick jab test to determine the air lock and proceed with bleeding"

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1 Answer

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Sounds like a thermostat and/ or the system is low on coolant.
Its probably not going to reach 200 degrees when the outside air temp is below freezing, but you should get plenty of heat if the system is working correctly.

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Heater isnt blowing warm air in 2003 grand caravan


Assuming the radiator is full of coolant, you are describing a faulty thermostat. The thermostat is closed when the engine is cold to restrict coolant flow until it warms up.

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My 99 pontiac montana has a heater problem.after engine is warm the heater blows warm air for a few minutes and then blows cold for a few minutes and then warm again. sometimes it blows warm for a few...


I would change the Thermostat. if that doesn't fix it? I would buy a Radiator flush and follow the directions exactly you will be surprised how much junk comes out. That should fix all your heat problems.

Jan 07, 2011 | 1999 Pontiac Montana

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I have a 2001 dodge stratus and the heater only blowed cold aire now we changed the thermostat and it blows warm air when idling but when driving still blows cold need some help please


where did you buy your thermostat? if you bought a fail-safe style thermostat it could have been no good before you even put it in. also is your tempeture gauge coming up to operating temp?? if it isnt your thermostat may be stuck in the open position allowing the coolant to circulate freely and not actually warm up. i would also check the lines going into the heater core. if one line is hot and the other line is cold than your heater core is probably in need of a flush or replacement.

Dec 01, 2010 | 2001 Dodge Stratus

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When my car warms up the heater blows out warm but gradually gets cooler and cooler after about 10 min. It will stay cold ( about three degrees above outside temp.) It does this on cold days. And after you...


It may be the valve that controls the amount of water entering heating core but I'm wondering if your engine thermostat isn't stuck open. This is what controls the coolant temperature in your engine. It closes off while engine is off. It will remain closed after you start your car until the water warms to a certain temperature then it starts to open enough to keep your car at the proper operating temperature. If it stick open then it will take a lot longer for the engine to heat up and on smaller cars might never heat up enough for your heater. If you live in very cold climates such as where I live in Wyoming, we have to change to a higher degree thermostat so we have a good heater when it's 30 below zero.

Be very cautious here but one way you can check this is to put a piece of cardboard in front of your radiator and stop the airflow that cools your engine coolant. THIS WILL CAUSE YOUR CAR TO HEAT UP AND CAN CAUSE ENGINE DAMAGE IF IT OVERHEATS. Don't completely cover the radiator but if your heater warms up when you put the cardboard in front of radiator it's a good sign that your thermostat is stuck open and needs to be replaced.

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2 Answers

Heater blows cold air. also, the temperature gage


A thermostat stuck in the open position can cause both of these problems

Nov 12, 2009 | 2002 Chevrolet S-10

1 Answer

Heater blows cold air


With the car warmed up,feel the heater hoses,are they both warm/hot near the firewall in the engine compartment?If they are both warm/hot,then the heater core should have circulation through it and it may be a "blend door" issue in the heater a/c assembly.If they are not warm/hot then the heater core could be dirty and plugged up and needs to be flushed.
If the above does not help,a drain and vacuum of the cooling system and vacuum refill will remove any trapped air.
Sometimes,clamping off the top rad hose and holding the engine rpm at 2000 rpm will force trapped air out of the heater core.(Watch temp gauge when trying this)
Lastly,a NEW thermostat doesn't mean its working correctly.

May 18, 2017 | 2005 Lexus SC300

1 Answer

Heater only blows warm air.


The hoses from your heater core should be very hot to the touch. Check the hoses going to the core from the water pump. It should be very hot. The return hose should also be very hot. Now check the hoses going to the core. If they are not the same temp, then your heater control valve is not working correctly or the vacuum is not working. At any rate, locate the vacuum line going to the heater valve. Remove the silver bar on the valve from the plastic plunger arm. You will have heat all the time now if it was only a vacuum problem. You can fix it later when it's warmer out. BTW a 200* thermostat will make your heater even hotter.

Nov 21, 2008 | 1998 Jeep Cherokee

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