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'98 GTP with dual climate control no heat on driver/ luke warm on passenger

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pigskinzen

New member
My 1998 GTP has no heat on driver's side even when setting LED to 90 degrees; set passenger to 90 degrees and some warm air comes out of the vent. Both heater hoses going to the heater core are hot at operating temperature; however I flushed the heater core.

It only takes a few minutes to go from nothing to running at 230+ degrees F, but no heat. Low coolant light on, so I added coolant to overflow reservoir. I opened the radiator cap and started the vehicle adding one gallon of anti-freeze/coolant when it was running. Replaced cap and let it warm to 220+ degrees F, no heat.

Nothing that I have done has changed the fact that no heat is available. Today was record high of 65 degrees F but tomorrow it is forecasted as 35 degrees F for high and 20 degrees F for low.

Please help!
 


I'd make sure the blender doors are moving to allow the heat to enter the cabin.

Also make sure the middle vacuum line on top of the supercharger tree isn't broken anywhere as it enters the cabin. That vacuum line works with the HVAC system.

It would worthwhile to bleed the cooling system from the thermostat housing screw to make sure no air is trapped up high.
 
How do I make sure the blender doors are moving to allow the heat to enter the cabin?

How do I make sure the middle vacuum line on top of the supercharger tree isn't broken anywhere as it enters the cabin?

How do I bleed the cooling system from the thermostat housing screw to make sure no air is trapped up high?
 
Also, why was the low coolant light on? You either have an external leak somewhere or the LIM gaskets may be bad letting the motor slowly eat it, which if this is the case you need to fix it asap before you spin bearings and look for a used motor. Have the LIM gaskets ever been changed on it?
 
I believe that LIM indicates a "lower intake manifold" gasket???? If so, no I have never torn into the motor to replace gaskets. I have not seen anything unusual when changing oil that would indicate an internal leak of coolant that would degrade the viscosity of the synthetic oil that I use. In other forum posts I have read that the idiot light for low coolant was generally a sensor which commonly failed on 1997-2003 Grand Prix models.

I have never seen puddles of coolant or anything else that signals an external leak. Is there any other way of testing before I tear into the motor?
 


All things point to the blender door actuator on the driver's side which appears to be a b%@!^ to get too if you have the hands of an American male over the age of 12 years. I am concerned about the low coolant level especially if it is leaking into the motor oil. I guess that I will have to park it until the weather changes and then tackle this mess when we thaw.
 


i wear 3x gloves and got to mine more then one time. aka i got huge ass hands and sausage fingers.

if you take the metal cover off under the plastic under the column you can peek in and see the actuator, then reach under and take its bolts off and its dumb little plug. you will need a light under there even in the day time.

once its off you can turn the knob by hand to make it give heat or cold air, the knob only moves a 1/2 inch or so. dont try to force it.
 
pull the oil dip stick if its just oil its fine. its the na engines that eat the coolant via a failed upper intake.

top it off, keep an eye on it.

if its full the coolant sensor in the rad could be dirty and tossing a false signal too.

when topping it off it might be best to run it cap off till the fans come on, this way you know the t stat is open and coolant is flowing through the engine. when th et stat opens i could take more coolant. then check it cold the next morning, it should full to the top of the cap maybe even spill out a bit.

also make sure the over flow tank has coolant in it too. if it leaks, theres your coolant loss.
 
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Thanks, all good ideas. I was suspecting that the overflow reservoir was a possibility but I have never seen any puddles underneath the vehicle. I am praying for an "easy" fix so that I do not have to tear into the motor. I'll update the thread after testing this weekend.
 
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