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Over heating still :( radiator or Pump?


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Hi all,

I just drove from San Francisco to Vancouver with the heater on most of the way. my 87 gl was running within the top 3/4 of the heater gage most of the way. I replaced the thermoswitch in SF thinking I had found the ultimate problem, now I am wondering if the pump is shot or if the radiator is plugged.

 

Symptoms: Ran hot going up hills even at high RPM's. Grill was removed and fan switch was jumped to be on all the time the car was running. It would run hotter the faster I went. Around 60 it could take pritty well (bit over half my gage) when going 75-80 it was really hot and would get very close to red when doing hills in the middle of the oregan day.

 

I am at a loss with radiator/pump except that RMP's didn't make a very noticable difference, then again I am not sure how much it should make a difference. This is a test I was told for checking the pump????

 

Thanks for the help. Other than the heat she ran like a champ with a full load.

 

Pleasantly supprised with my new car,

Nathan Chase

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2 fixable possibilities: Air bubble (did you check coolant levels after stop/cooldown?) and plugged radiator. The radiator is pretty easy to get a feel for, literally: While the engine is running (careful!!!), run your palm from top to bottom of the radiator core, feeling for temp differences. This is more difficult if you have A/C. If the radiator is plugged you will likely feel hot and cold bands across the radiator. If there is a cold band right at the top of the radiator it COULD be due to low coolant level. If the radiator is evenly cooler than expected it could be a sign of flow issues somewheres else: T-stat or air bubble, maybe HG pressurizing the system.

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Sounds like a plugged or otherwise inefficient radiator.

 

More RPM's may speed up the cooling flow as the pump goes faster, but it also increase the power required, therefore the amount of heat to be dumped. To test the bad pump idea, you have to try running at the same speed with higher RPMs, not increase the speed at the same time. At 80 mph, you need roughly double the horsepower, therefore double the heat to dump, as at 60 mph.

 

To test the water pump with this more rpm idea, try going 50 mph in 5th for a while, then see if the temperature drops when travelling 50 mph in 4th.

 

Rob.

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87 GL so this is an EA81 not an EA82 right?

 

how old is the thermostat, it could be plugged.

are the fans blowing the right way?

any leaks or coolant loss? is the coolant full?

i'd guess the radiator is plugged then the water pump.

most older subaru's have bad radiators. not many that i see have what i'd call reliable and decent radiators. look for greeen corrossion.

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if you have the digidash, ive heard tell that you might have a faulty gauge reading as well.. you might want to look into that. harbor freight sells a little point and click laser guided infrared thermometer, my uncle has one.. handy for checking the radiator flow, too..

 

clicky for the harbor freight thermometers, 40 bux. nice tool to have around, and forty bucks for a chinamart one that might break, but with care and infrequent use (most of us) should last a while at least. the flexi-shaft one even comes with a case, so did my uncle's.

 

just a thought, its something that comes in handy when building your car. (thats what i think of fixing my subaru as.. strange huh?)

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