Overheating? - Maintenance and Repair Forum

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Overheating?
Friday, January 15, 2016 11:38 PM
I was just wondering if anybody has had a heater core be the cause of overheating in a pre-ecotech cavalier.
I currently have a 99 that I'm on wits end with. I've done the radiator,cooling fan motor (with a trash autozone one that caused massive horrid vibrations) then again with an OEM motor that fixed that problem,water pump,head gasket,new coolant cap+ reservoir, multiple system flushes,and I've gone through about 8 thermostats. At this very moment I run it with no thermostat, so I don't have an overheating problem, I just have no heat at all. My last guess would be that the heater core has a clog in it, not allowing the thermostats to open. If I'm seeing it correctly, there is a separate pipe that splits off just outside of the radiator, before the thermostat that also loops back in, just before the thermostat. Is it possible that a blockage in the heater core would keep the cooler coolant trapped, until it's actually forced through, not allowing the thermostat to open, as all of the cold coolant temporary blocks the heated coolant from reaching the thermostat? Sorry if I seem a bit repetitive,I just don't have any other straws to grasp at, I'm just also trying to hype myself up for probably swapping my heater core, unless somebody can point me in another direction to a problem similar to this that they've had. If it adds any detail,I've also added one of those nifty little LED exact temperature gauges onto my dash, for a while I was able to run a 160 degree thermostat (slightly trimmed down) but often the car ran at 170-195, until it decided it would not stay below 200 furthermore. The guage also gets it's reading before the thermostat, and the branch off of the heater core, and often read the 170-195 as stated before. Any tips, or ideas in general are greatly appreciated.

Re: Overheating?
Saturday, January 16, 2016 10:11 PM
Have the same issue with my 99 cav. Never did get it fixed. Just turn ur heat on when it heats up. Been running 3 years this way


ReD RaiN
Re: Overheating?
Sunday, January 17, 2016 10:40 PM
I'm hellbent on fixing it now, since I've already gone so far, I just get no in between,not having a thermostat means I run at ~120F, and with it in, it jumps too ~220F in a matter of minutes. I'm just curious if anybody else has had this, or has any ideas other than what I've already done.
Re: Overheating?
Sunday, January 24, 2016 12:05 AM
Does your cooling fan turn on? It could be a heater core blockage, but it would be shooting the pressure somewhere. usually it would cause a coolant leak in the interior.

The pre ecotec 2.2's were also notorious for head gaskets. Have your engine cold, take off the coolant reservoir cap. Start er up, and see if you see any kind of bubbles inside the bottle. or if it starts to overflow.
Re: Overheating?
Friday, February 05, 2016 11:23 PM
Nicholas Reilly wrote:

Does your cooling fan turn on? It could be a heater core blockage, but it would be shooting the pressure somewhere. usually it would cause a coolant leak in the interior.

The pre ecotec 2.2's were also notorious for head gaskets. Have your engine cold, take off the coolant reservoir cap. Start er up, and see if you see any kind of bubbles inside the bottle. or if it starts to overflow.


The fan is a little funky, as in it sometimes turns on early, From all I've tested, never late, The headgasket has already been replaced, although I've never had any exhaust come up in that system, when I had the head off, there were no signs of a warped or cracked head or block. I've done a little bit of calling around, and have had a one guy encounter it being the heater core causing it to overheat,I'm almost convinced this is it, since it's the only thing left, but I guess I'll be back with updated when I finally get around to doing it, It's my luck that I bought the 1/1,000,000 cavalier that has this happen,lmao.
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