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2002 Outback Sport
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Discussion Starter #1
My 2002 OBS is currently experiencing a overcooling problem. It does not reach operating temperature within any reasonable amount of time, and any heat it does gain is lost if I press the accelerator down. This occurs immediately, and even when the car does not accelerate rapidly enough to suggest cold air being the issue.
The frustrating part is that I've replaced the thermostat twice, once with and without an OEM part.
I've tried replacing the MAP sensor, the hosing, I've cleaned the IAC valve.
Nothing is working. I'm frightened the high revving caused by this will burn out my clutch, or worse.
 

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The subaru of many acronyms
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could try covering/blocking like 1/2 your radiator in the front with cardboard if you want a simple fix, worked for me when i had my rs in michigan and it wasnt warming up

as for the more complicated explanation of why this is happening? couldnt figure it out on mine so cardboard it is when temps get cold.
 

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2002 Outback Sport
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Discussion Starter #3
Honestly I would like to avoid doing that, but it may be the only option left to me. At least until I can find out what exactly is happening.
 

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2001 Coupe
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I'm frightened the high revving caused by this will burn out my clutch, or worse.
Please explain the above.

I'd start by running it cold with the radiator cap open to see if you have water flow. If so, it's still a thermostat issue.

If the flow doesn't start once the block is warmed up then I'd start looking for air in the system or a possible water pump issue.

If neither of verify your coolant temp sensor is working correctly and you have enough antifreeze in your system versus water.

If this is all something stemming from the recent sub zero temps I'd look for a way to keep some heat in the system. Cut airflow to the engine bay, especially if you have an rs hood, then block off a portion of the grill.
 

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2001 Impreza 2.5RS+T 2001 Legacy GT
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Is it possible for the thermostat in these to be installed backwards or just incorrectly at all? Because the way it sounds, you just don't have a thermostat at all.

If there was air in the system it would register at the H on the gauge.

If neither of those are the case, covering half of the radiator with a piece of cardboard is the way to go!
 

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2002 Outback Sport
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Discussion Starter #6
Please explain the above.

I'd start by running it cold with the radiator cap open to see if you have water flow. If so, it's still a thermostat issue.

If the flow doesn't start once the block is warmed up then I'd start looking for air in the system or a possible water pump issue.

If neither of verify your coolant temp sensor is working correctly and you have enough antifreeze in your system versus water.

If this is all something stemming from the recent sub zero temps I'd look for a way to keep some heat in the system. Cut airflow to the engine bay, especially if you have an rs hood, then block off a portion of the grill.
What I meant is that, until the car warms up properly, the car will idle high and also not drop down to idle when the clutch is depressed. I'm afraid it's doing damage.
I've already verified I have enough antifreeze, but I haven't tried leaving the radiator cap off and seeing if there's flow. The problem is that wouldn't a lack of flow cause overheating, not overcooling?
 

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2000 2.5RS/C BRP
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What I meant is that, until the car warms up properly, the car will idle high and also not drop down to idle when the clutch is depressed. I'm afraid it's doing damage.
I've already verified I have enough antifreeze, but I haven't tried leaving the radiator cap off and seeing if there's flow. The problem is that wouldn't a lack of flow cause overheating, not overcooling?
If, before you start driving the car, you gently touch the accelerator pedal, the RPM should fall to normal idle.
 

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2002 Outback Sport
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Discussion Starter #8
If, before you start driving the car, you gently touch the accelerator pedal, the RPM should fall to normal idle.
It does, but during driving it will not fall down to idle, and will sometimes actually climb.

I just went out and ran the car with the radiator cap off and the results were confusing at best.
The coolant rose from the radiator cap opening and overflowed. I put the cap back on, and let the engine heat up.
Here's where it gets good. The top hose and the radiator itself? Nice and hot. The hose from the thermostat? Dead cold.
I revved the engine a few times, and any time it rose above 3k the temperature dropped like a stone. This is while stationary.
 

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2000 Impreza RS
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It does, but during driving it will not fall down to idle, and will sometimes actually climb.

I just went out and ran the car with the radiator cap off and the results were confusing at best.
The coolant rose from the radiator cap opening and overflowed. I put the cap back on, and let the engine heat up.
Here's where it gets good. The top hose and the radiator itself? Nice and hot. The hose from the thermostat? Dead cold.
I revved the engine a few times, and any time it rose above 3k the temperature dropped like a stone. This is while stationary.
it could be possible the radiator could be clogged. since removing the radiator is so damn simple, I'd take it out and run water through the top and see if it comes out the bottom. Plus you'd be flushing out the radiator so you'd do two things at once.

I'd say to check the piping from the waterpump to the heater core/ to the engine. if those two pipes are clogged it could cause some temperature problems, usually overheating but wouldnt hurt to burst some air in there to see if the lines are clear.

How is the pressure on the hoses? Are they crazy tough? or normal pressure where you only need a little effort to squeeze with one hand? If its real tough, you may have a kinked coolant hose closing off the hot water.

if all the water continues to pressurize outwards, you may have to check compression, usually when the water overflows through the radiator while its cold it means theres a compression leak into the coolant system.
 

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2002 Outback Sport
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Discussion Starter #10
if all the water continues to pressurize outwards, you may have to check compression, usually when the water overflows through the radiator while its cold it means theres a compression leak into the coolant system.
Which would imply a headgasket issue, right?

I only ever gave the top hose a squeeze, never thought to do more than touch the bottom hose. Next time I head out I'll check that. Hopefully it's something simple like a clog rather than a gasket.
 

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-a clog would overheat the car, the coolant in the engine wouldn't be getting moved so it would get overhot. Both coolant sensors are on the top side of the engine close to where the hottest coolant is leaving before it goes into the radiator.
-the sensor the engine reads from could be faulty (or unplugged), causing the ecu to THINK the engine is actually cold and keep the idle high

Is the gauge reading normal? The gauge has its own one wire sensor and the engine computer has an independent two wire sensor.

The top hose should be hot, that is the coolant leaving the engine. The bottom hose should be WAY cooler, it is after the radiator has cooled it and before it enters the block. The thermostat slows the coolant coming into the block and regulates its temperature.
 

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I mean reading in the middle of the temperature gauge...where it normally would be. This would mean the coolant is actually at operating temperature and not too hot or too cold. If you let it idle for about ten minutes (because its obviously super cold outside right now) does the coolant gauge get to the middle?
 

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That code apparently means the ecu thinks the coolant isn't warming up quickly enough, that is why the idle is staying high...because the ecu is making it stay high. If you already replaced the thermostat with an oem style, it should be staying closed and getting the coolant to warm up. You may have air in the system which could be allowing the sensor to read incorrectly, or the sensor could be faulty. If you have any type of coolant leak or if your coolant overflow line is loose it could be pulling air in every time the car is off and cooling down.

I worked on a chevrolet with a code that said the same thing, I changed the thermostat and that was it. It had an aftermarket thermostat that wasn't closing all of the way and not letting the coolant get warm fast enough for the ecu. Funny thing is, we used an aftermarket thermostat :lol: but at least it was a known good one.
 

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2002 Outback Sport
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Discussion Starter #15
It does eventually heat up but it takes quite a long time, and loses heat as the throttle is opened.
 

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Does the coolant gauge get colder, or just the heater in the car or both? If its both, I suggest an oem original new thermostat. Not a colder or hotter one, but the recommended exact oem one from the dealer. The quality is way better than aftermarket, it is rare for them to go bad.
 

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2002 Outback Sport
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Discussion Starter #17
I actually think only the guage falls, and not the heat from the vents. And as my first post said, I've already put in an OEM thermostat. This is the thermostat the car is currently using.
 

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2000 Impreza RS
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When the engine is hot, turn on your heat. If the heat inside goes away as you hit the gas then you def know you have a problem. If the heat stays the same inside as it cools off on the gauge then you can rule that the sensor could be faulty. Makes sense that this should let u know exactly what it could be.
 

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2002 Outback Sport
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Discussion Starter #19
I can tell you right now that the heat does not fall along with the gauge. Seeing as the sensor is one of two things I haven't check yet, it looks like I might have my fix.
 

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Remember, the dash gauge may run on a seperate sensor. Its likely the engine has a two wire sensor and the gauge has its own one wire sensor. If the car is throwing that code and the gauge is dropping, the temperature is actually too cold.
 
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