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2001 Subaru Outback
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Discussion Starter #1
Hi I’ve been trying to pinpoint the overheating problem I’ve been having lately. It’s getting to 100 degrees here in vegas so this issue just started to appear.

So far I’ve done.

-Coolant Flush + Subaru coolant conditioner
  • OEM Thermostat (old one was aftermarket) I was hoping this would solve the problem.
  • OEM radiator cap
The car runs fine at operating temp for a long time under normal driving conditions, it first started to overheat when eating at a food truck, and running the ac with the car in park for about 30 min straight.. perhaps I trusted the car too much... lol it started to rise towards the H and I immediately cranked the heat with ac off and the temp returned to normal. I was unable to turn the ac back on the rest of the trip home because it would start to rise in temp again.

When I did the flush the fluid looked clean with no signs of anything mixing in there that shouldn’t...

All fans are turning on so that isn’t the problem.

My next hunch is the radiator being clogged???

I’m going to attempt to burp the system again with a spill free funnel. Because I burped it without the funnel and it felt too easy to do... considering I’ve read how hard it is on these cars...

I am at a loss to be honest. I really hope it’s not the Headgaskets, I’ve seen a couple threads suggesting that. But I’ve also seen that these HG leak internally so there’s not much I can do until I get it fixed.

I’d appreciate any help I can get guys!


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Discussion Starter #2
More context, it is overheating under the same conditions before and after all the parts were replaced above. Only difference is today when overheating under the same circumstances I noticed the overflow spilled over. But I believe I overfilled the tank on the initial fill up. There is still bubbling in the overflow tank when looking at it. But not all the time. (Only when the stat is open? I’m not sure)


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Outbacks, SVXs, XT6, 4Runner, Celica, Brat, E150s
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Running hot at idle is a very abnormal head gasket symptom. It's usually much worse under load.

Running hot at idle is usually an airflow problem. The H6 fans are 2 speed, are they running on high? Plug in the diagnostic connectors and see if they run at 2 speeds.

The radiator is a tighter matrix than the A/C condenser. So debris can travel through the condenser and clog the radiator. I'd pull the radiator and rinse it (back to front) out really well with a hose. And inspect the core for any signs of corrosion or damage.

Also worth doing, would be to have an OBDII reader/dongle in the car to check the temperature through the ECU when it acts up just to verify it. Although it sounds like the symptoms are pretty consistent, so it's probably accurate.
 

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Discussion Starter #4 (Edited)
I’m pretty sure the fans are turning on both speed but will double check it.

I have a feeling it’s the radiator purely through process of elimination lol. I’m getting the spill fee funnel and obd scanner this Saturday so I’ll be able to burp it while seeing the temps.

When I flushed the coolant I ran a garden hose through the radiator from the upper radiator hose to the lower. And water came out... could the radiator still be clogged? I’m not familiar with the internal details of radiator, are there different sections that could be clogged? Specifically the section that’s needs flow when the ac is on?
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Check the front of the radiator for obstructions/debris.

Over time a build up of debris accumulated between the air conditioning condenser and the radiator and partially blocks the radiator so it cannot “breathe” properly.

Seagrass
 
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The clog I'm thinking would be debris in the fins that would block airflow, like this:


That's an extreme example (just from a google image search), but you see what I mean.

I don't know if it's worse on Subarus than other vehicles, but we saw it many times at the dealer where I worked. Visual inspection of the cooling package looks fine (you can only see the condenser) in the car, pull the radiator and it's packed with debris. This would obstruct airflow, which would be most evident when not moving...
 

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Discussion Starter #9
Took out the radiator and cleaned it. Definitely was some debris I could see. Got the pressure washer and got all that off. Hopefully when I test drive it it’ll make a difference



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Yuck....that wasn't working very well.

Hope it works better!
 

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Discussion Starter #11
Yuck....that wasn't working very well.

Hope it works better!
Yeah it seems to have helped. Although it has cooled down outside a bit. I’ll have to make sure I have no problems when I gets back to 100+ degrees soon!


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Discussion Starter #13
So the car started to overheat again today while waiting in line at the sams club gas station... not sure what else I could do. Cranked the heat and floored it to cool it. Got it on the highway and traveled across town with no overheating on the highway. Back to city driving and after sitting at a long light it got hot again.


Any ideas on where to go from here?


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Discussion Starter #14
Checked the overflow tank and it was filled to the top... not much went back in to the radiator at all. It actually spilled over. Other than that I see no visible leak that’s losing coolant. Radiator was Loretta low though so I got the turkey vaster and put some in from the overflow then topped it off.


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2001 VDC/SC One of a Kind
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Seems you need a new radiator cap. When the overflow fills up and doesn't get sucked back in to the radiator when the car cools it indicates a bad cap. Same thing if you see a radiator hose flattened after the car cools. The cap is holding the vacuum created when the coolant cools down and contracts instead of pulling the coolant from the reservoir.

Did you get the system burped good?
 

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Discussion Starter #16
I purchased a new OEM cap from the dealer about 2 weeks ago, at the same time as the tstat. I’m sure I burped it correctly had the spill free funnel and scanner. Watched temps as the thermostat opened and closed multiple times. Ran heat as well


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Then I suggest you check the hose in the reservoir. It may be sucking down to the bottom of the reservoir. To remedy this you would cut the bottom of the hose at a 45 degree angle.

The engine could be overheating under pressure due to an internal problem; head gasket breech. At idle the coolant doesn't circulate as quickly and heat and pressure build in the block faster. The pressure escapes via the cap to the reservoir.

Don't see many HG issues with the H6, but it does happen when there are repeated overheating events, or one long one.

What you described with it overheating at idle and staying cool while running is also an indication of a low volume of coolant in the system, or cooling fan operation issues.

In the case of the fans, check the battery condition and alternator output. Low current flow will not allow for the fans to operate at high speeds. Make sure both fans are working.
 

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Discussion Starter #18
Then I suggest you check the hose in the reservoir. It may be sucking down to the bottom of the reservoir. To remedy this you would cut the bottom of the hose at a 45 degree angle.

The engine could be overheating under pressure due to an internal problem; head gasket breech. At idle the coolant doesn't circulate as quickly and heat and pressure build in the block faster. The pressure escapes via the cap to the reservoir.

Don't see many HG issues with the H6, but it does happen when there are repeated overheating events, or one long one.

What you described with it overheating at idle and staying cool while running is also an indication of a low volume of coolant in the system, or cooling fan operation issues.

In the case of the fans, check the battery condition and alternator output. Low current flow will not allow for the fans to operate at high speeds. Make sure both fans are working.
If the fans cycle through all speeds when plugging in the diagnostic cables below the dash then they should be operating correctly when running right? I will verify if they kick into high speed today though


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Discussion Starter #19
So both fans are working... cut the coolant tube at an angle. Drained the coolant to the cold indicator on the overflow and topped off the radiator.... took a semi long city drive and while it didn’t overheat, the overflow was near the top again. Waited a night for it to lower... its still at the same level.


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You have a leak/hole somewhere that is allowing air to be sucked back into the radiator instead of coolant from the coolant overflow bottle.

You mention you have a new radiator cap so there could be a hole in the coolant overflow hose or the overflow hose may not be making a good seal to the radiator. Of course you could also have another faulty radiator cap too (but unlikely)

Seagrass
 
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