I have a 98 silverado for my work truck, and it had problems heating up and the temp gauge would rise all the way to the top, then it would drop all the way back down, then climb back up to where its supposed to be but it only spits out hot air from the heat vents for a minute then it turns cold again.. I am leaking antifreeze, and I do not know where it is coming from. My temperature continues to fluctuate between normal and hot while I use it but never show signs of over heating? It doesnt seem like anything is mixing in with the oil. I pulled the dipstick and it looks clean. What should I check on this thing to get down to the problem? Thanks

 

Sounds like your thermostat is on its way out...must be sticking. Check that . Is it leaking from your overflow?
Check around your water pump also for leaks. If it is wet around the water pump there is your problem......I would also change the thermostat at the same time.

 

i agree start with the thermostat and if it still does it after you change that it is time to move on the the next big thing which is the water pump. it may be possible to have a blown gasket but if there is no signs of antifreeze on the block then that is ruled out.

It is good that your oil is still fine also cause that rules out a blown headgasket which is a major pain.

i think you just have a bad thermostat with a bad gasket causing the leak.

 

^^ Ok thanks alot I am going to check it out when I get home and let you know what I find. I will check where the wet spots are when I get home.

 

One thing not mentioned is a bad freeze plug. Easy fix if you can get to it.

 

My brother had a silverado and was having this EXACT same issue. I'll get with him and see what he found.

 

If you have a blown head gasket you would know as soon as you start your car and drove it.... Big white smoke would be very noticable....not the smoke you see when your car is cold in the morning.....it would be 5x worse.

 

i thought about saying this as an option but you mostly can trace the leak to a freeze plug easily, as well as back to the thermostat housing. i dunno i got the flu and my mechanical thinking is not so hot right now

 

I figured I mention it because it doesnt seem like hes even tried to trace it other then looking at the dipstick. More options the better I guess.

 

Im not saying it is a bad option to check, but i do agree that he should get under the hood and take a real good look around and try to trace it down.