Overheating problem

I have a 98 Grand Am GT. The damn thing keeps overheating. I replaced the water pump about a month ago to fix a leak. It worked, but it kept overheating. Then I blew a head gasket. I used K&W Block Seal and it sealed it up. But it keeps overheating. So I tried pulling the thermostat out. I didn't replace it, I just took it out. It's still overheating, but not at such a dramatic increase in temp. There's no leak at all and I know this for sure because the reservoir is still retaining coolant.

The only thing I can think of that it might be is that when I used the engine block sealant, it sealed up something else that it shouldn't have. So I think it's just a pressure problem because if I pull over while it's overheating and remove the coolant reservoir cap, the temperature goes down some. I also disconnected the hose that connects to the overflow pipe from the reservoir. It seemed to not be overheating as quickly as before. That is what leads me to believe it's a pressure problem. So any ideas on the problem/solution? Please and thank you.

You could try flushing your cooling system a few times. That sealer might have clogged the radiator and or heater core.
Since its overheating with the thermostat out you have some issues ! Could have a cracked head.

Idealy you would want to replace the head gasket(s) and have the head(s) inspected thoroughly.

Good Luck.

First off, you want a thermostat in it. The water will cavitate without the restriction there, you get air bubbles in the system, and you overheat. Test your thermostat. If it opens at 192 degrees, it's fine and can be reinstalled. As cheap as they are, however, I would put a new one in as long as it's out.

And yes, flush that sealer crap outta there!

So I think it's just a pressure problem because if I pull over while it's overheating and remove the coolant reservoir cap, the temperature goes down some. I also disconnected the hose that connects to the overflow pipe from the reservoir. It seemed to not be overheating as quickly as before. That is what leads me to believe it's a pressure problem. So any ideas on the problem/solution? Please and thank you.

Try replacing the pressure cap, it does sound like it may be too low on pressure, which can also cause the water pump to cavitate.

That hose you disconnected... it's the one that's about 4" long and has an open end hanging down? Removing that should make no difference whatsoever. If you mean the hose/pipe that goes from the thermostat housing to the reservoir, you just found your problem. That's an air bleed and is needed to get all the air out of the system. Normally, coolant constantly flows through it. If you removed it, and you don't have coolant pouring out of it, find the restriction and correct it.

Another thing, are you sure it's overheating? Check the actual temperature and compare that to the guage. If you removed the cap while it was overheated, you probably would have been burnt by the steam and escaping coolant, which makes me wonder about the guage. Also, if it was actually overheated, the coolant would have boiled over when you removed the cap. The pressure in the system allows to coolant to be at a higher temperature than it is capable of at atmospheric pressure, removing the pressure from the system would make the water go from 260 degrees to 212 degrees instantly, which makes all the coolant in the system boil to release the heat that it cannot hold.

And yes, flush that sealer crap outta there!


Try replacing the pressure cap, it does sound like it may be too low on pressure, which can also cause the water pump to cavitate.
Is there something I can flush it with that'll work better than water?
I did replace the pressure cap. So that's not it.

If you mean the hose/pipe that goes from the thermostat housing to the reservoir, you just found your problem. That's an air bleed and is needed to get all the air out of the system. Normally, coolant constantly flows through it. If you removed it, and you don't have coolant pouring out of it, find the restriction and correct it.
That is the one I disconnected. There is coolant flowing through it and air is coming out. That's why I disconnected it.

Another thing, are you sure it's overheating? Check the actual temperature and compare that to the guage. If you removed the cap while it was overheated, you probably would have been burnt by the steam and escaping coolant, which makes me wonder about the guage. Also, if it was actually overheated, the coolant would have boiled over when you removed the cap. The pressure in the system allows to coolant to be at a higher temperature than it is capable of at atmospheric pressure, removing the pressure from the system would make the water go from 260 degrees to 212 degrees instantly, which makes all the coolant in the system boil to release the heat that it cannot hold.
How can I check the temperature?
Another thing, when I did remove the cap, it did steam and coolant did boil over. And it did hurt. I just unscrewed the cap little by little until I could take it off.

We use a flush kit from BG, it's not very expensive, but you really should use their machine with it to make sure you get all the cleaner out, so you may just want to go with water. It won't get any deposits out, but at least you won't be sealing up any more coolant passages.

That hose is the automatic air bleed, it needs to be connected to the reservoir or you'll have air trapped in the system. The coolant is pulled back into the system from the bottom of the reservoir, so all the air gets separated out. If air keeps coming out of it and never slows or stops, you probably have a bad head gasket or cracked block. If a head gasket is just beginning to leak, it can let exhaust/air into the coolant but not coolant into the cylinder. It's not necessarily a leak, it could just be air from the water pump cavitation because of low pressure or cavitation where the thermostat should be. If you want to leave the thermostat out, break out the springs and stuff in the center and install just the flat metal piece, that will provide enough restriction. I don't know for a fact that these engines need a thermostat in place, but I know a BMW I-6 needs one, and so do older GM V8s at high RPMs... I'd put something back in there just to eliminate that possibility.

I use an infrared thermometer pointed at the thermostat housing as close to the LIM as possible. Lacking that, I suppose you could put a cooking thermometer on the upper hose and wrap some foil around it :dunno:

You can buy cooling system flush products at your local parts store. 1-2 bottle should clean the system up , but some of that sealer may never come out even with a power flush.

Also I havnt noticed to much "overheating" when the thermostats are removed. I do this regularly when flushing the system so you dont have to wait for it to warm up to circulate. Though I dont drive it that way, it does get a little warmer sitting and running.

You can test the thermostat by placing it in some boiling water on the stove, should open rather quickly. As J-Ri said they are not that expensive.

Even trapped air will make it over heat. My GT just done this a little the other day untill it burped a couple times.

Good Luck rdeckert !

Also I havnt noticed to much "overheating" when the thermostats are removed. I do this regularly when flushing the system so you dont have to wait for it to warm up to circulate. Though I dont drive it that way, it does get a little warmer sitting and running.


It gets worse and worse the higher the engine RPM is, driving the BMW I refered to, it would overheat even with the RPMs below 2,000, but was fine at idle for 10 minutes then gradually crept up.

I originally used the block sealant to seal up the busted head gasket. If I try to flush all the crap out, will the head gasket just leak again? I would replace it, but I don't have the money to get it done. I would do it myself, but I don't have anywhere to do it because I live in an apartment complex.

I use an infrared thermometer pointed at the thermostat housing as close to the LIM as possible. Lacking that, I suppose you could put a cooking thermometer on the upper hose and wrap some foil around it
What is the LIM?

Lower intake manifold- LIM