K
kabhold
I have a 00 sunfire and it's overheating. Changed thermostat, and water pump. Still overheats but stable arounf two twenty. Radiator stays cool no matter how long it runs. ??
wde3477
Member
Are you sure the thermostat is opening? Some can be faulty out-of-the-box, particularly the bargain brands.
Are the radiator innerds clear - not fouled with corrosion or other gunk?
Could it be a faulty temperature indication? Does the motor 'feel' hot?
Has the coolant system been properly bled and is it full?
Are the radiator innerds clear - not fouled with corrosion or other gunk?
Could it be a faulty temperature indication? Does the motor 'feel' hot?
Has the coolant system been properly bled and is it full?
K
kabhold
I want to flush the radiator but thes no cap. So how would I do that?
K
kabhold
Ok nm. I did a flush, replaced the thermostat with yet another one, and changed the coolant sensor. Still overheating. Radiator never gets hot. Coolant is full. I'm at a loss.
______________________________
wde3477
Member
Always difficult to gauge a member's mechanical skill level in these forums - so don't be offended -
Essentially thinking of three main possibilities here - thermostat not working for whatever reason, water pump not moving the coolant, or there is a blockage in the flow path - with high suspicions toward the radiator.
Are you sure you put the thermostat in the right way - typically with the spring side facing / going into the motor? It will not work correctly if installed backwards. If you put the thermostat in a pot of boiling water - does it open up?
The next suggestion is a bit messy - but may want to remove the thermostat housing and thermostat, leaving the rest of the system full, and start the engine very briefly to verify the water pump is moving water. It should flat move quite a bit, at least until it sucks the radiator dry. If you try this, you may wish to drain and to save the antifreeze, and refill with water for this part.
Have there been any bypass hoses removed, rerouted, or capped off? Not sure what your exact vehicle has - but these bypasses as well as the heater hoses are important for circulating the coolant inside the block and through the water pump while the thermostat is closed. Helps to maintain a more even temperature throughout the engine, as well as give the thermostat a more accurate temperature to work with.
Is there any reason to suspect the fan belt is installed incorrectly, turning the water pump the wrong way?
If all checks out so far, would look hard at a plugged radiator. It sounds like you have the system where the pressure cap is on the coolant reservoir, so this makes things a little more tricky. Suggest to drain the radiator and to remove the upper and lower hoses from the radiator. Then stuff a garden hose in the upper inlet on full blast and see how fast it comes out the lower side. If you can figure out a way to put more water in faster, using a bucket and a large mouth funnel or the like, then go for it. If the upper inlet reservoir side fills up and overflows, you definitely have some core blockage. The water should easily come out the lower end as fast as it goes in the upper.
Hang in there - all problems are solvable - it's just that they can be really frustrating until the solution is found.
Good luck, and keep us posted!
Essentially thinking of three main possibilities here - thermostat not working for whatever reason, water pump not moving the coolant, or there is a blockage in the flow path - with high suspicions toward the radiator.
Are you sure you put the thermostat in the right way - typically with the spring side facing / going into the motor? It will not work correctly if installed backwards. If you put the thermostat in a pot of boiling water - does it open up?
The next suggestion is a bit messy - but may want to remove the thermostat housing and thermostat, leaving the rest of the system full, and start the engine very briefly to verify the water pump is moving water. It should flat move quite a bit, at least until it sucks the radiator dry. If you try this, you may wish to drain and to save the antifreeze, and refill with water for this part.
Have there been any bypass hoses removed, rerouted, or capped off? Not sure what your exact vehicle has - but these bypasses as well as the heater hoses are important for circulating the coolant inside the block and through the water pump while the thermostat is closed. Helps to maintain a more even temperature throughout the engine, as well as give the thermostat a more accurate temperature to work with.
Is there any reason to suspect the fan belt is installed incorrectly, turning the water pump the wrong way?
If all checks out so far, would look hard at a plugged radiator. It sounds like you have the system where the pressure cap is on the coolant reservoir, so this makes things a little more tricky. Suggest to drain the radiator and to remove the upper and lower hoses from the radiator. Then stuff a garden hose in the upper inlet on full blast and see how fast it comes out the lower side. If you can figure out a way to put more water in faster, using a bucket and a large mouth funnel or the like, then go for it. If the upper inlet reservoir side fills up and overflows, you definitely have some core blockage. The water should easily come out the lower end as fast as it goes in the upper.
Hang in there - all problems are solvable - it's just that they can be really frustrating until the solution is found.
Good luck, and keep us posted!
K
kabhold
The thermostat is in correctly and opens in boiling water. I haven't tried flushing the radiator with water yet. Why does the heater blow cold air when idling then hot when revying the engine or driving? Fan belt is installed correctly as per diagram on the car. As for hoses... i haven't changed anything and they all seem to connect one thing to another. idk. Ill try flushing the radiator with a hose tomorrow.
Thx for all your help!
Thx for all your help!
Last edited:
wde3477
Member
Low heater output can be a sign that all of the air is not out of the system. This may clear up somewhat as the engine RPMs rise as the water pump is turning faster. It can also be a sign that you have a vacuum line leak in your HVAC control lines, if you have a vacuum actuated temperature blending damper.
Again, not sure about your particular setup, but many times on engines that won't naturally pass air to the radiator, there is a bleed screw or the like by the upper coolant outlet of the engine to aid in getting all the air out. There may also be a special coolant fill procedure to follow - not sure if that would be in the owner's manual, or if you would need to grab a look at a shop manual such as Chilton's, Haynes, Motor, or GM.
If you haven't already - you may consider pulling the upper thermostat housing, and pouring coolant in to fill the block up. If it's possible, may as well pour coolant through the upper hose to fill the radiator, then connect everything back up. If when you pull the housing, there isn't coolant that comes out, or at least is full up to the top of the engine - you may have found your problem.
Again, not sure about your particular setup, but many times on engines that won't naturally pass air to the radiator, there is a bleed screw or the like by the upper coolant outlet of the engine to aid in getting all the air out. There may also be a special coolant fill procedure to follow - not sure if that would be in the owner's manual, or if you would need to grab a look at a shop manual such as Chilton's, Haynes, Motor, or GM.
If you haven't already - you may consider pulling the upper thermostat housing, and pouring coolant in to fill the block up. If it's possible, may as well pour coolant through the upper hose to fill the radiator, then connect everything back up. If when you pull the housing, there isn't coolant that comes out, or at least is full up to the top of the engine - you may have found your problem.
K
kabhold
Ya nm. It was my girlfriends car and we broke up. It got towed away. Thanks for your help though!
______________________________
wde3477
Member
Ouch! Well, I suppose that's one way to solve the problem. 