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Hi, 

My 1990 american legacy wagon I've just bought has an over heating problem. It drives fine and the coolant temp stays slightly below the centre of the gage on all flat and downhill roads no matter how much you thrash it. It's only when I drive up a hill that it slowly starts to overheat. If I pull over and let it idle it will go back to the normal operating temp in less than a minute, as soon as I start driving up hill again it starts to overheat. It doesn't seem to matter how much I accelerate, it seems like the only thing that makes it heat up is going on the up hill slope. Does anyone have any clue what could cause this? 

Thanks 

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Low coolant level

Clogged/compromised radiator.

 

100% predictable overheating symptoms are a sign of a reduced internal circulation rates or reduced efficiency of existing mechanisms.

and it makes perfect sense - climbing a hill is extremely taxing (just push/pull/carry something very heavy on flat land then try up hill - the difference is enormous) - it may be only then that a 50% capacity radiator can't dump enough heat.

 

in order of most likely to least likely this means:

1. compromised radiator (usually clogged)

2. stuck thermostat

3. debris impeding air flow from the grille to radiator

 

but guessing isn't always good so:

 

you can run a garden hose through the radiator. I like to compare it side by side with another radiator, but a good radiator should flow all, or most, of a garden hose turned all the way up but that's somewhat dependent on radiator and hose flow rate.

 

test thermostat in a pan of boiling water. replace with OEM.

 

1. verify coolant level *in the radiator* isn't dropping over a period of time.

an internal headgasket breech will eventually result in declining coolant levels.

2. verify no leaks

3. make sure radiator cap is functioning properly.

4. verify fans but you seem to think they're fine.

5. i've never seen this happen but just to be sure make sure the front of the vehicle, a/c condensoer, radiator fins aren't clogged/impeded by cardboard or debris.

Edited by grossgary

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Check level of coolant : check the rover tank is filled to the line.

 

Sharply squeeze the upper radiator hose. You should hear the giggle pin in the thermostat. You should feel water resisting the squeeze. You may hear air gurgle. If it feels or sounds like only air, that has to be dealt with. A normal good non leaking system should have no air at all, or maybe a tiny amount.

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Depending on the geometry of the system on your car, opening the radiator cap indruduces air, which is why I don't check by opening the cap unless there is no coolant in the upper hose.

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This is a classic symptom for which people spend way too much money on.  Its the radiator cap, pure and simple.  Its not holding pressure, just get a new one.

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If you get a thermostat, get OEM or high grade Stant.

 

Other cheaper ones have been known to cause problems.

  • Like 1

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I don't recommend the stant.  Either use the Subaru one, or you can go to NAPA and ask for their Altrom line.  That one is made by Tama, an OE manufacturer.  There is a significant difference in size and weight between those and your normal aftermarket ones.

 

Cap is worth a shot.  They're only designed to last about 5 years, and a lot don't even make it that far.  Especially here at higher altitudes, you can run into a problem where, without the added pressure on the system, the coolant can boil within the normal operating temperature of the engine.

 

Radiator is also a good place to start.  Make sure that air can flow through it as well, and that the fins aren't all flattened out.  Doesn't matter if the coolant is flowing good if the air can't flow over it to cool it.

Edited by Dj7291993

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Yes replace the cap. If the radiator is more than 10 years old just get a new one. Get a Koyo radiator and a good Japanese cap. Get the thermostat from the dealer or if you can find it, a Tama brand one.

 

GD

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