[Harvey Kreider]

On my 92 when the temp. gauge starts to rise (mostly at idle) the heater starts to blow cold air instead of the warm air it was blowing. Once the car is moving again the temp guage goes back to normal and the heater blows warm air again. What is the relationship? Blown head gasket or a cracked head or what. Any ideas on this? Appreciate any comments.

 

[B-Lo]

Try bleeding the cooling system and refilling, worked for me

 

[KNLNGUS]

Harvey Kreider - I agree with Blo.

If bleeding any air out of the system does not work, try buying bars stop leak and repeating the process before further diagnostic such as replacing the tube that leades from the radiator to the reservior.

Gotta jet. time to go home

KNLNGUS.

Good luck.

 

[Dv8]

Radiator Checklist

Check the radiator cap for any rubber deterioration underneath,

-if there is some visable damage to the rubber replace the whole cap.

-add water to the radiator till it tops off.

-bleed air valve(top radiator hose)

-Also check the heater control valve for leaks(back against the firewall below the intake manifold.

-if persistant Replace thermotat

-thermostat sending unit(on botom of radiator)

-Make sure your radiator isnt leaking

-check headgasket by doing a compression check and/or leak down test.

~Hybrid

 

[warren C]

Another DIFINITIVE test for Headgasket Failure

-check headgasket by doing a compression check and/or leak down test.

~Hybrid

Another sure-fire test for headgasket failure is to take the car to a mechanic who also does smog checks. Make sure the engine is fully warmed up...its even better if you've been driving for a while. Also make sure you've got a good radiator cap..no leaks allowed.

Your mechanic can use his smog "sniffer" to test for hydrocarbons (combustion gases from the cylinder) getting into the cooling system...he sticks the "sniffer" probe into the air space at the top of the coolant reservoir. If HC's are detected in the reservoir air...they can only get there by leaking past the headgasket.

To me this is a lot easier to understand than compression and leakdown tests. Leakdown can also be caused by rings and/or valve problems..and you or your mechanic really need to know what you're doing to tell what's really going on and know the difference.

There's also a simple chemical DIY hydrocarbon test kit that you can buy from most MAC or Snap-On tool trucks. About $55.

It's kinda' like a "turkey baster" thing ....a glass tube with with a rubber squeeze bulb at the top. Pretty simple device. You put a special chemical inside of the glass tube of the turkey baster ...it also has a fat hard rubber cone shaped nozzle at the otherend . Warm the car up to full op temp. Then jam the cone shaped end into the filler hole of the coolant reservoir and squeeze the rubber bulb....this sucks air from inside the reservoir into the glass tube and it bubbles up through the chemical.

If there are hydrocarbons in the air in the coolant reservoir...the chemical turns color (blue I think)....indicating HG failure.

Warren C