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Discussion Starter #1
Hello I have a 2004 Forenza that has an over heating problem in the summer/spring and runs at half the normal operating temperature during fall and winter. When it over heats it is running at about 120 km/h and running at about 3500 rpms. This car has a standard transmission and has no a/c. I am beyond confused and frustrated with this thing and any help with it would be greatly appreciated. I am out of ideas!
 

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Could be a combination of things..

Running too cold is usually caused by a stuck open thermostat. A stat that is sticking or slow in any manner can cause both undercooling and overcooling - its a cheap place to start your investigation. I would try replacing this first.

Also as Max mentioned... you could have a clogged / dirty radiator that isn't transferring heat efficiently enough to keep the car cool when the temperatures are hotter outside. Combine a poorly functioning stat with this and it would create the problems you are talking about.

Have you ever put any of those "stop leak" (or any other) additives into your cooling system? They can really make a mess internally and degrade the overall efficiency of cooling.
 

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Discussion Starter #7
No I have never ran anything like that through it. I guess I will try the thermostat. I have repaired the Heater core in this car twice in two years and have struggled to get the air out of the system. Just seems like air just keeps turning up in my cooling system so I actually have had to loosen off my overflow cap just a touch so my system doesn't pressurize so much. Could this be attributed to some form of intake leak?
 

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Could this be attributed to some form of intake leak?
Or cylinder head (combustion pressure) leak. :(

I still wouldn't rule out the radiator too, with regards to the high speed overheating. #1 cause!
 

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Something else that piques my curiosity is the need for you to have "repaired" the heater twice.

The core I assume, which leads me to believe that the coolant system has suffered from lack of anti-freeze maintenance (fresh inhibitors, flushed ever? resultant debris build-up).

Your thoughts? :)

How many miles on this vehicle?
 

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Discussion Starter #10 (Edited)
Well I have changed the heater core twice, first time may have been from a lack of maintenance and I think the second time may have been when I installed the heater core it was a real pain in the ass to get in so it was jammed in there pretty hard. So the antifreeze now has been changed several times since last winter. When you say combustion leak are you suggesting the head is cracked, head gasket blown or both? I have tried multiple times to purge the air from the cooling system but it just keeps finding it's way back in there. There is no antifreeze in my oil and I don't seem to be losing any antifreeze. I have right around 180000 km on this vehicle.
 

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I think that a coolant system pressure test is in order, to rule out leaks.

 

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theres definitely some kind of a problem with they system. you should be getting ZERO air in it. its considered a closed system which basically means little to no maintenance for the life of the car. the other thing that i find strange is your need to have the overflow cap loosened. the coolant overflow tank needs to be the highest point in the entire system . this allows for any air to be purged from the system through the pressurized cap on the tank. i would definitely try the pressure test and try a new thermostat. im starting to wonder if the problem isnt with the water pump
 

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well if working to hard or has a broken piece it could be churning up the water. maybe the water tank cap isnt working and releasing the air as it should. but in theory the air should still be in the tank and not in the system. maybe there is a problem with how the hoses are and theres a high spot in the system or a hose with a kink in it. check the firewall connections and make sure theyre tight. you mention youve had to bleed the system, you really shouldnt have to it should do it itself. try removing the water tanks cap and inspect the water tank neck and cap, make sure theyre not cracked or split. check the service manual and make sure all the hoses are hooked up to the correct inlets/outlets.
 
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