Engine overheating\ cools down when rpms get to 4000
Replaced thermal stat, still overheat, took it out, got second opion, installed another new one, ran good for about an hour, overheating again, but, this time i figured out that the higher the rpms got the lower the temp needle would go down. o.k. so canadian tire the first place said it's probably the head gasket and said if i want to run the car, but with no heat to take it right out and that's what they did. second guy said maybe a faulty thermal stat, doubted it was the heat gasket. he istalled the second thermal stat and i reported the high rpms thing and now he says it's obvious that the radiator is plugged. i have a parts car, so i can get that rad out or should i get the one thats in there now flushed. does anyone agree with the second mechanic? the car engine sound good and runs good with lots of power.
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Re: engine overheating\ cools down when rpms get to 4000
I would get a radiator flush and fill to make sure the radiator is clear and clean. it could be a head gasket if you were losing lots of water but i dont think thats the case.get it flushed out and go from there
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Let's start with the simple and make sure the coolant mixture was 50/50 and not 100% coolant. That will make it overheat.
Second, thing I would check is if there's a code for your catalytic converter or oxygen sensor. If your converter is clogged, then it builds back pressure that overheats the engine.
Hopefully that helps. That's all I can think about without actually having done the head gasket replacement myself or having inspected the vehicle. And make sure the heads were resurfaced and inspected as well.
First thing first, change your radiator thermostat, but make sure someone does it after the car is completely cooled down. Youll need to replace or top off the radiator fluid. If you are mixing the radiator fluid , make sure to use distilled water if it is concentrated fluid and asks for water. There are too many minerals in spring or tap water. If your car really is overheating,its a must to change your oil asap. A took an auto shop course where the instructor said that when a car overheats, the engine oil breaks down and deteriorates, and becomes no good. Everytime your car overheats= oil no good.
also check and make sure your radiator resevoir is full to the right line cuase maybe it just needs new fluid or if its been 50 -70k on the same radiator fluid, I would have it flushed, there could just be an air bubble in the line.
Was the engine overheating before you replaced the thermostat ? By not putting the cap on tight, you are not allowing the cooling system to build up pressure. So it could be a restriction somewhere like a radiator hose.
sounds like the air in the cooling system was not all bled out , it should correct itself after a few drive cycles, if not then there is more than likely a problem with the thermostat sticking in the closed position.if there is not sufficient coolant inside the cylinder head then the tempature at the thermostat will not be enough to open it therefore the cycle of the coolant will cease causing an overheat and possible engine damage.
Strangely enough,if you remove the thermostat in the Northstar engine, it will overheat, this is because the stat is both a thermostat and a pressure valve.I can't be bothered to explain in detail how the whole cooling system works but please understand that you need to put the stat back in,(or preferably a new one).As for the cooling fans,what you described is normal for the Northstar. Further to this, look at my profile,I have provided similar solutions for overheating problems.
I had the same overheating problem in my jeep ! My problem was finaly found out to be the clutch in my fan its a different kind of clutch system it work as this. When your jeep gets warmer the tighter your fan clutch gets .While cool your fan moves slowly. now to test your clutch just warm up your jeep and rev it up a bit if your fan dose not pick up speed then it is sliping.What will come out of this is that you fan will the seez and run full all the time. if you jeep dose not overheat wile moving then it is not your thermo stat period.