thermostat makes it overheat?

[GreenMystChevy]

okay, i put a 350 in my truck from a friend but before I threw her in, I put on a new set of heads. We throw the motor in, start her up and everything is fine, until we watch the temp rise until it is just about hitting the other side. Shut that thing off, took out the thermostat and she runs cool as can be.

All great until now, when it gets cold in the morning going to work. I buy a new thermostat, put it in, same thing. Just heats up. All of the hoses get nice and hot except for the top one, the one with the thermostat. What gives? I need this thing to warm up, especially for the girlfriend.

Thanks for the help guys.

[boilrman]

Are you sure you are installing it correctly? and that you have a 180 or 190 degree thermostat.(I think that is what it is suppose to be)

All I can think is you are putting it in upside down.

Good Luck

[GreenMystChevy]

I know that i am putting it in the correct way, I even looked at the box it came in to make sure, putting the spring dealy on the bottom. And yes, the thermostat is the correct degree setting, I made sure of that too. This is frustrating.

[O'l Buck]

possibly t-stat is in upside down as stated above(copper colored sender thingy goes down)......a good way to test the stat to see if it's working properly is to fill a coffee can full of water, put a long bolt or something over the top of it and hang the t-stat off a string into the water, then, put it on the stovetop and heat the water to the desired temp (should open at 180 if it's a 180 degree stat), if it don't open at 180, give it a chance, might go at 185 or whatever.

quite possible you got a defective thermostat.

[Andy4639]

Did you fill the motor good with water and coolant. If you have any air in the lines it will do this. You need to bleed all the air out and make sure the water pump is pumping the water. When the air gets to the thermstat it will act like a pocket and not let the water flow.

Hope this helps Andy

[Longhorn Man]

Posible you have a bum temp guage and don't realize it. Get a cheap one from auto zone and install it either peminately or just for trouble shooting.

[GreenMystChevy]

OK, the thermostat is a 195 and that is what the guy behind the counter said when he looked in his book. I know that they screw up here and there so can you guys tell me which one i should get. Would it hurt to go a little lower, like a 180? Any other reasons why this does this?

Also, how do I clean out the system, you know, g et the air bubbles and stuff out?

Anyways, after I go pay for another one, if that does not work, I guess I'll spend the few bucks on a temp gauge. I hate this nickel and dime stuff. This is also a pain because it is my daily driver so I have to find time to do this stuff. Thanks guys.

[Fred T]

If you do not have the thermostat in, check the temp gauge by running the truck until it gets warm. Leave the radiator cap loose so you can open it when hot. You might need to block the radiator with cardboard to help warm the engine. Then put a thermometer in the radiator to get a temp reading, it should be pretty close to the gauge. If not, first replace your sending unit. For a thermometer I use a meat probe for grilling meat, cost is around $5. You can use one from the kitchen, just wash it off good and put it back without the wife knowing!

If you drain the coolant just enough to replace the thermostat, you shouldn't have to worry about bleeding the system. Easiest thing to do is to drill a small hole in the thermostat, which will let the air out. And I would run a 180 deg stat unless I lived where the temp never got about 70.

[bobs409]

I would follow longhornmail's advice. Buy a gauge with actual numbers on it and see what that reads. If everything is working correctly, the thermostat should open when it hits its listed temp. 195 for a 195 stat, etc.

BTW, about 245 is considered overheating in all reality. I doubt you hit that high as there would be steam for sure. I'd shut down by 230 myself!

[dmec]

while you are checking temp with a thermometer check to see if water is being circulated. maybe a bad water pump. removing t stat reduces restriction and requires less flow. just a thought

[jhow66]

Here is the way to get all the air out---take themostat and drill a small hole in the outer edge--this way as the water rises the air will bleed off thru this hole ( will not affect operation of themostat). Your engine is getting hot because there is a air pocket below the themostat--not hot water. Block water will boil before the themostat will open if it is this way. Hope this helps.

[Tink]

Whatever you do, definitely take FredT's and jhow66's advice and drill a small hole in the edge of the t-stat. I just did that the last time I put a t-stat in my S-10... it runs about 165-170 with a 180 t-stat in it and I don't have any problems with air pockets.

[71GMC_3/4T]

It's also a good idea to run 50/50 antifreeze & water. That will keep it from boiling too.
I agree with everyone else on the little hole idea. Air will get through that little hole real fast and go to the top of the radiator where it belongs. When the T-stat's closed, there won't be enough water getting through the little hole to make a difference.
And put some clothes on your girlfriend! No, wait, I think I see where you're going with this... "Whew, sure is warm in here! Maybe you oughta take that fluffy sweater off... There, that's much better!"