Coolant Problems

Hi, I recently purchased a 93 suburban 4x4 with tow package that has 90k miles on it. This past weekend I took it up to the mountains to go skiing. Every time I went up a mountain pass the temp. gauge went through the roof. A couple of times I could here the coolant boiling in the over flow resevoir. As soon as I backed off the gas and nursed it along the temp dropped right back down. At times it would even drop down to 120 degrees.?.? I am not really sure where to begin with this problem, if anybody has any suggestions I would greatly appreciate your input.

thanks in advance
sean

Is the radiator full of coolant? Is the fan belt tight and in good shape? Does the fan turn fast enough?
Is there trash, leaves, etc between the radiator and A/C condensor? How does the engine run? Any misfire, water (other than normal condensation) coming out of the tailpipe? Is there a thermostat in the engine and is it working properly?

Answer these for starters.

Sounds like a head gasket.

another thing to look at //// rad core possibly plugged

thanks for the replies. i have checked all the fluid levels and replaced the thermostat. i was driving around town today and the temp. shot through the roof. no hills or anything just pancake flat driving. do you think flushing the system might work?

i am having the same problem with my 88. i have tried every thing with the best results coming from replacing the fan cluch, though i am now suspecting a blow head gasket

i actually had blown a head gasket, and then later found out that i had cracked the head. that one hurt the wallet.

I am having the same problem with my 93 suburban. It overheats quickly when ac runs but overheats also when ac is off, just takes a little longer. I have taken out the termostat and replaced water pump with no luck. How do I check to see of the radiator core is plugged? I dont see any debris on the front of the radiator. I have had a problem with my front heater core breaking (4 times since Jan) so could a new radiator solve my problem? Thanks!