96 Jimmy thermostat rising on idle

[TWW66]

Hello. I just bought a 1996 GMC Jimmy with a few issues. Since I'm not rolling in cash I'm hoping to manage some of the repairs myself. First out of the gate is the temperature problem that I didn't notice a couple days ago. The Jimmy starts smoothly and there are no strange noises coming from the engine aside from the serpentine belt squeaking which I will have replaced this week. At stop lights with/without foot on the brake the thermostat begins to rise and once got high enough to cause the check engine light to come on. Once The light changes and I drive a little ways the heat drops back down to normal. This reminds me of motorcycle behavior where the air-flow is needed to maintain a normal engine temperature. I have limited mechanical knowledge but I'm willing to learn. For reference, the last time I stuck my head under a hood to do anything more than fluid checks, vehicles didn't have computers. Any assistance at all would be greatly appreciated.

 

[Molson02536]

Hello. I just bought a 1996 GMC Jimmy with a few issues. Since I'm not rolling in cash I'm hoping to manage some of the repairs myself. First out of the gate is the temperature problem that I didn't notice a couple days ago. The Jimmy starts smoothly and there are no strange noises coming from the engine aside from the serpentine belt squeaking which I will have replaced this week. At stop lights with/without foot on the brake the thermostat begins to rise and once got high enough to cause the check engine light to come on. Once The light changes and I drive a little ways the heat drops back down to normal. This reminds me of motorcycle behavior where the air-flow is needed to maintain a normal engine temperature. I have limited mechanical knowledge but I'm willing to learn. For reference, the last time I stuck my head under a hood to do anything more than fluid checks, vehicles didn't have computers. Any assistance at all would be greatly appreciated.

Fan clutch could be bad and may need to be replaced or your radiator may need to be replaced cause of the crystal formation from the Dexcool antifreeze. Start with the simple and flush out your cooling system with Prestone radiator flush.

http://members.shaw.ca/betterthanyoutoo/dexcoolflush.htm

Keep us posted, at worst the water pump could be worn out and good luck.

Molson02536

 

[thechaz05]

I have the same problem. I also have to constantly put coolant in the radiator. the reservoir tank is always full, but the rad is not. I bought a new thermostat thinking that it was sticking, but when I tried to change it I could not get the bolts loose and broke my adapter in the process. Of course now it's dark when I leave for work and dark when I get home so I am hoping I can make it till this weekend. Could the thermostat be sticking? I am hoping to be able to flush and fill the system at the same time I change the thermostat.

 

[Molson02536]

I have the same problem. I also have to constantly put coolant in the radiator. the reservoir tank is always full, but the rad is not. I bought a new thermostat thinking that it was sticking, but when I tried to change it I could not get the bolts loose and broke my adapter in the process. Of course now it's dark when I leave for work and dark when I get home so I am hoping I can make it till this weekend. Could the thermostat be sticking? I am hoping to be able to flush and fill the system at the same time I change the thermostat.

If its not a bad leak, put 2 table spoon of common table pepper in your coolant. This should help stop any leak for now and and the pepper washes out of the system easy. Buy a bolt extractor to remove and replace the broken bolt you have. Just make sure your have a drill and the right size bit.

Try location where the leak is and inspect your engine oil and transmission fluid for any signs of coolant mixing in the system. If your lucky, the coolant is leaking from a frost plug or a slow leak from the weep hole from the water pump.

At worst, your intake gasket is leaking or worst your radiator has gone bad and the oil cooler or transmission cooler has failed and coolant is leaking through there and mixing. Also replace your radiator cap, sounds like its also seized up and not allowing the coolant in the reservoir to replace the loose of coolant.

Good luck and keep us posted.

Molson02536

 

[thechaz05]

If its not a bad leak, put 2 table spoon of common table pepper in your coolant. This should help stop any leak for now and and the pepper washes out of the system easy. Buy a bolt extractor to remove and replace the broken bolt you have. Just make sure your have a drill and the right size bit.

Try location where the leak is and inspect your engine oil and transmission fluid for any signs of coolant mixing in the system. If your lucky, the coolant is leaking from a frost plug or a slow leak from the weep hole from the water pump.

At worst, your intake gasket is leaking or worst your radiator has gone bad and the oil cooler or transmission cooler has failed and coolant is leaking through there and mixing. Also replace your radiator cap, sounds like its also seized up and not allowing the coolant in the reservoir to replace the loose of coolant.

Good luck and keep us posted.

Molson02536

Thanks for the reply Molson, we can always count on you.

To clarify though, what I broke was the socket adapter, not the bolt. Anyway, I was able to stop by my buddies shop to have him put the thermostat in and look at the problem. What we found was evidence of leaking from intake gasket (was not pouring out or anything like that, just evidence of coolant there.) He pressure tested it and it held pressure and was not losing pressure so I am good there. I need to replace the gasket, but I think I can wait till winter is over. We replaced the thermostat, the fan clutch seemed to be ok and was engaging. After replacing the thermostat my gauge was no longer fluctuating and it definitely was not overheating anymore. It actually runs cooler now.

Thanks again buddy