heater control valve


Old 08-12-03, 04:44 PM
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heater control valve

Hi there i was just wondering if you could point me in the direction of the heater control valve?on 1990 3.1 chev cavalier 5 spd.Im having a bugger of a time finding out what my problem is.Everyone i talk to doesnt seem to think its the head gaskets.Instead the cooling system is air locked.I have no heat after changing heater core,thermostat,coolant,hoses.And still no heat.Today i started the car no het again reved it up under the hood apx. 5000 rpm's and voila heat.I figure BONUS.I go for a drive constantly checking the heat it was working fine then........No heat then......TEMP light and it overheated.PLEASE PLEASE help me......
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Old 08-12-03, 04:49 PM
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I don't believe it has one

Whoa Nelley. Have the radiator boiled out by a shop, that's #1. #2 change your radiator cap. #3 Make sure the water pump is in good shape. Look for signs of coolant stains/liquid at the weep hole.

#4 any shop can easily confirm a bad head gasket with a cooling system tester or a gas analyzer. Autozone can probably rent you the former if you want to check it yourself.

#5 Only use GM/Delco thermostats---you may have gotten a defect!
Old 08-12-03, 05:54 PM
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Join Date: May 2003
Location: USA
Posts: 1,459
It sounds like you have air in the system. Some cars can be difficult to bleed the air off. You might want to see if you can rent or borrow an airlift to bleed it. Barring that, what else have you done to the cooling system? I remember a little about your previous post, but not alot. Refresh out memory. Thanks.
Old 08-12-03, 06:37 PM
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90 cavalier

Hi there Billy,I have changed the cap,water pump,thermostat,heater core,and a few hoses.Its just getting a little frustrating now.Im open to any suggestions.The info i get from you guys NEVER does any harm.So let me have it...LOLBy the way my oil has no coolant in it thats visable,and vise versa.It has a sputter once in a while but i ve think i have a bad wire.Another problem another day.No biggie.
Old 08-12-03, 06:42 PM
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Getting the air out can sometimes be a majorP.I.T.A... Try squeezing the upper hose to try and move the air bubble, try doing this with the cap on but loose (1st position) that will allow the air to escape easier. As someone else suggested try elevating the front end.

If none of this works, take the thermostat back out and make sure it was put in right side up. Believe me it is an honest mistake and has been done before. Another old trick is with the stat out of the car put an aspirin in the stat to hold it open slightly. This will allow the air to move while the car is warming up, and the water will naturally disolve the aspirin.

Good Luck!!
Old 08-12-03, 06:49 PM
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Join Date: Jan 2003
Location: Arkansas
Posts: 469
Joe's right..No heater control valve..It's a constant flow, and "doors" turn on and off the heat inside the plenum..
If memory serves correct, there should be a couple places to bleed the cooling system on that car...One should be on the thermostat housing.. Small brass screw, or a 7mm headed "bolt"..
The other bleeding point should be on the bypass pipe right next to the water pump..again, a 7mm headed "bolt"..

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