Temp gauge and heater

I have a 97 Gt with 126k. I noticed that when ever my temp gauge reads 150+ the heater starts kicking out cooler air. The lower my temp gauge reads like at or below 150 the hotter the air is. Also the temp gauge constantly varies from 140 to 210 degrees, so I have hot air one minute, cool air the next. What's going on?

You can check calibration of the ECT - Engine Coolant Temp sensor. How old is your thermostat? Do you still have the original UIM Plenum and intake gaskets? Check for air or combustion byproducts in the cooling system.

You can check calibration of the ECT - Engine Coolant Temp sensor. How old is your thermostat? Do you still have the original UIM Plenum and intake gaskets? Check for air or combustion byproducts in the cooling system.

1. Still have the original UIM plenum and intake gaskets and don't plan on changing them. This car is 14 years old and already has many little problems not worth the money. If I don't have them change could they "outlast the car"?? Another small problem is the car burns oil. It burns about 45% of the only in 3k miles so I guess it doesn't matter if it burns oil because I get it changed anyway??

2. Thermostat is 3 years old, so a broken tstat could be the problem????

You can check calibration of the ECT - Engine Coolant Temp sensor. How old is your thermostat? Do you still have the original UIM Plenum and intake gaskets? Check for air or combustion byproducts in the cooling system.


My temp gauge can go from 140 to 220 in a matter of 5 seconds, do you thing this is more of a tstat issue?

YOur stat could be sticking closes. Once the temp builds past 140, it just keeps on going up until coolant starts to boil. I'd start cheap and replace the stat. Make sure you bleed all the air out of your coolant system when you get done. Also it may not be a bad time to flush your heater core.

YOur stat could be sticking closes. Once the temp builds past 140, it just keeps on going up until coolant starts to boil. I'd start cheap and replace the stat. Make sure you bleed all the air out of your coolant system when you get done. Also it may not be a bad time to flush your heater core.

Well I just got my oil changed and the service tech said my coolant was bone dry. This is obvs the reason my temp gauge was going way up. My dad put coolant into my radiator probally 1 month before this. He had me start the car and turn the blower on, is this the right way to add coolant?? ............ I guess my best bet now is just to keep a eye on my temperature gauge.

you're going to have to change the intake gaskets if you don't want to blow this car's engine up. You most likely need a new UIM as well as they were a known issue on the 95-98 Vik-K 3800's. There is an issue with the EGR stovepipe melting the UIM, causing internal coolant leakage. There is no repair, replacement is necessary. If you're in it this far, you'd be best served to change the lower intake gaskets as well, because if they aren't blown yet, you're on borrowed time and it's only a few more bolts to get the lower intake off while doing the UIM.

you're going to have to change the intake gaskets if you don't want to blow this car's engine up. You most likely need a new UIM as well as they were a known issue on the 95-98 Vik-K 3800's. There is an issue with the EGR stovepipe melting the UIM, causing internal coolant leakage. There is no repair, replacement is necessary. If you're in it this far, you'd be best served to change the lower intake gaskets as well, because if they aren't blown yet, you're on borrowed time and it's only a few more bolts to get the lower intake off while doing the UIM.

How much do the UIM parts and lower intake gaskets cost if I buy them online? And how long should the job take for an experienced mechanic?

you can get an aftermarket UIM from Dorman for around $100, and the lower intake gasket set should run you about $50.

you can get an aftermarket UIM from Dorman for around $100, and the lower intake gasket set should run you about $50.


How long should this UIM and lower intake job take a qualified mechanic?

the last one I did took me between 3-4 hours total (including all the clean-up).

Hey guys back again with temp gauge issues. Let me first say that it has been close to 90 degrees where I live. The temp gauge when driving fluctuates from about 210-225 degrees. When stopped the gauge creeps up to almost the boiling point marker. Any ideas ??

Also my service engine soon light came on, could they be related ?? Usually the light is an error message (piece of carbon on some part I was told) and goes away in a few days. The light has only been on 1 day so I will keep that updated.

Hey guys back again with temp gauge issues. Let me first say that it has been close to 90 degrees where I live. The temp gauge when driving fluctuates from about 210-225 degrees. When stopped the gauge creeps up to almost the boiling point marker. Any ideas ??

You had a coolant leak over a year ago....what was done to fix that ?

Also my service engine soon light came on, could they be related ?? Usually the light is an error message (piece of carbon on some part I was told) and goes away in a few days. The light has only been on 1 day so I will keep that updated.

A pice of carbon has your SE light on? Who told you that crap? If the light is on, a code is set....you need to have the code read, to know what direction to go in next.....