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Ok so here I am again and getting driven insane!!! I love my subaru but am ready to trash heap it! lol 

 

 

1991 Legacy Wagon

 

intermitent overheating

 

Fluids look great, thermostat replaced twice by me, newest being OEM, Not losing water/coolent, yes the car is actually getting hot so not just the gauge, fans come on when ever I check for it, but a new development, this last time that it overheated for no reason the heat/ac fan inside the car sudenly stopped working! All fuses that I know of are fine ( both under the hood and under the dash).  So for the upteenth time yesterday it over heated, refused to cool off even after letting it coolf or a while and restarting it, so I left it sit overnight thinking I would have it looked at today. Instead I thought I would try to see if it would run, and *poof* not even hint of overheating on the 10 mile drive home!!! 

 

 

Could all of this be due to a bad computer? or would a bad heater core poss cause this? 

 

Help!! lol 

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My money would be on bad head gaskets. I had a 91 that did that, sometimes over heat, sometimes not. It had a mind of its own. Replaced the HGs fixed the problem.

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But why if its head gaskets would the heater fan studdenly stop? Or thinking is sepporate problems that just look like they are together?

Also I have checked and found no "bubbles in the overflow tank" that others are suggesting would be a sing of head issues, no oil in water or vise versa

Edited by MizzJesi

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Blower fan would be a different issue, nothing to do with the over heating. Sometimes when they blow head gaskets the heater will start blowing cold air, because of air/ exhaust gases stuck in the system stopping the coolant flow, but the fan would still work regardless.  When changing the thermostat to an oe, one did you burp the cooling system/ fill the engine first with coolant from the top radiator hose? There could still be air in system, some of them also have a bleeder valve in the top passeger side of radiaor, to help assit the burping procedure 

Edited by coolskaterkid

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Very important on these to get the engine and radiator full of coolant. Otherwise you run into issues with slow coolant flow which will cause the thermostat to close. If you didn't pour in at least 1.5 gallons of coolant the system is not full.

 

Clogged heater core may be possible but you wouldn't have heat if that's the case, and that wouldn't be intermittent.

 

The main cause of overheating due to bad head gaskets is because air and exhaust gasses displace the coolant in the system. Coolant is pushed out into the overflow and some is burned in the cylinder where the leak is. This causes a low fluid level in the system, which causes improper/slow flow of coolant. A water pump can't pump air, so any coolant that's stuck in the engine overheats because it is not moving out to the radiator to disperse that heat. As long as the system is kept full it will function, even with a bad head gasket, but when the level gets too low coolant flow is affected and the temp will begin to rise.

 

Blower fan is a separate issue. Usually a fuse. Possible the resistor block burned out, but that would usually leave you with only the highest fan speed.

Double check fuse for the blower (remove and test with an ohmmeter even if it looks fine. If not that possibly the fan motor just took the dirt nap.

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Very important on these to get the engine and radiator full of coolant. Otherwise you run into issues with slow coolant flow which will cause the thermostat to close. If you didn't pour in at least 1.5 gallons of coolant the system is not full.

 

Clogged heater core may be possible but you wouldn't have heat if that's the case, and that wouldn't be intermittent.

 

The main cause of overheating due to bad head gaskets is because air and exhaust gasses displace the coolant in the system. Coolant is pushed out into the overflow and some is burned in the cylinder where the leak is. This causes a low fluid level in the system, which causes improper/slow flow of coolant. A water pump can't pump air, so any coolant that's stuck in the engine overheats because it is not moving out to the radiator to disperse that heat. As long as the system is kept full it will function, even with a bad head gasket, but when the level gets too low coolant flow is affected and the temp will begin to rise.

 

Blower fan is a separate issue. Usually a fuse. Possible the resistor block burned out, but that would usually leave you with only the highest fan speed.

Double check fuse for the blower (remove and test with an ohmmeter even if it looks fine. If not that possibly the fan motor just took the dirt nap.

Agree, blower fan is a separate issue. When my blower fan quit, I went to replace it, and found old leaves and crud had washed down from the windshield to clog up the fan. Once I cleaned out the mess, the fan worked good as new. You would think the fuse would have blown, but no, the fuse was still good. Remove glove box to give access to the blower motor. Really pretty easy to work on.

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Ok thank you guys, coolent level is not low. So I guess to start I will empty and try to refill to make sure that I do not have air in my system. 

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If you're going to empty it, I'd put a garden hose to the radiator and be sure it's not blocked. If nothing else, you can often blow some gunk out ot there.

 

But yeah, keep adding coolant. Sometimes takes a while to properly burp the system.

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best cooling system purchase ever is a radiator filler funnel! locks in place so you can keep the cap off while filling and the engine is running. when I change my coolant I fill the block then the radiator turn the car on let it idle for 10 minutes while I add coolant till burped and topped off.   

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