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Old 08-30-2008, 05:53 PM   #1
ssslagle6006
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Default Overheating, Top Hose and Radiator Cap Cold

My car has been overheating for the past month or so. It started doing it only at idle and would cool off as soon as air started running through again. Then it started doing it while running. The coolant system isn't leaking and I had the thermostat replaced just over a year ago. The weird thing is that the top hose is cold to the touch along with the radiator cap when the car is overheating. Any ideas?

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Old 08-30-2008, 06:45 PM   #2
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Air bubble in system... Run it and burp it by squeezing the top rad hose gently as it warms up from a cold start with the rad cap off, Add coolant if it drops lower then normal as it flows.
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Old 08-30-2008, 06:59 PM   #3
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even though the t-stat was replaced a year ago don't rule it out as a culprit.
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Old 08-30-2008, 09:00 PM   #4
ssslagle6006
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Quote:
Originally Posted by flstffxe View Post
even though the t-stat was replaced a year ago don't rule it out as a culprit.
yes, but if it was the thermostat it would be the bottom hose that ran cold. the top would still be hot. plus this is a crucial racing thermostat which is designed to fail open to prevent overheating.
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Old 08-30-2008, 09:10 PM   #5
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Quote:
Originally Posted by ssslagle6006 View Post
yes, but if it was the thermostat it would be the bottom hose that ran cold. the top would still be hot. plus this is a crucial racing thermostat which is designed to fail open to prevent overheating.

in that case I would go with wrxdrvr and the air pocket theory.
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Old 09-01-2008, 09:04 AM   #6
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I have been having a similar cooling problem this weekend while racing and the problem was an air bubble in the system. I purged it by taking the cap of the reservoir on the left side of the motor (facing it) and idling the car until it purged all the air. The problem is that it keeps doing it everytime I do a circuit on the track. Anyone have any ideals about what is going on. I did notice that if I pull the cap off 5 or 10 minutes after the car has been turned off, there is no pressure. It fills the overflow tank up and starts to pull it back into the system as it cools, but doesn't get it all back. Obviously, there is a pressure leak somewhere. I changed the radiator cap, but that didn't help.

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Old 09-01-2008, 10:15 AM   #7
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Quote:
Originally Posted by ssslagle6006 View Post
yes, but if it was the thermostat it would be the bottom hose that ran cold. the top would still be hot
if there is no flow, how hot do you think the upper line could get? Sure it will conduct some heat from the engine through the coolant, but it's also connected to the radiator, which will tend to bring that temp down...

Is the coolant level ok? If you remove the cap on the tank on top of the engine is the coolant right to the cap (as with the lower cap)? If the system was full before, the overflow tank is full, and now the system suddenly has an air pocket, then there is almost certainly a leak somewhere (the coolant can't just "vanish")... Is the water pump functioning?
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Old 09-02-2008, 02:32 PM   #8
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The WRX is really sensitive to air in the system and it will do all sorts of weird things if there's air in there. Definitely start the car when it's completely cool with the upper resevoir cap off and let it idle up to temp, adding water if the level drops in the upper resevoir to keep it full. When it's about at normal temp, crank the heater to run coolant through the heater core to get any air out that could be in that part of the system and add more water if necessary. This should get any air out and you can pump that upper hose a bit while doing it but typically it'll fix itself if you let the car run to normal temp this way. Then you can drive it around, get on the gas a bit, bring it back and let it cool then take that cap off and make sure it's still full.

Might want to check the upper and lower hoses to make sure they're nice and snug. Sometimes if they're not, they'll actually suck air into the system and they wont even leak coolant!

Other than that, the water pump could be suspect... it might not be circulating the coolant properly.

It really doesn't sound like a thermostat issue. If it failed and was shut, the car would just overheat straight away and that's that. It would not go back and forth, it would overheat no matter what. If it locked itself open like ours is designed to do if there's too much air in the system or the temp exceeds a certain amount, it wouldn't come up to normal temperature at all and you'd get a check engine light.

Jeremy
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Old 09-02-2008, 05:18 PM   #9
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Headgasket for both of you? Especially for Serk03.
You might want to test your oil and coolant for cross contamination.
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Old 09-02-2008, 05:31 PM   #10
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Quote:
Originally Posted by DrD View Post
Is the water pump functioning?
how do i know if the water pump is functioning?
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Old 09-02-2008, 06:17 PM   #11
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Quote:
Originally Posted by Crucial Racing View Post

It really doesn't sound like a thermostat issue. If it failed and was shut, the car would just overheat straight away and that's that. It would not go back and forth, it would overheat no matter what. If it locked itself open like ours is designed to do if there's too much air in the system or the temp exceeds a certain amount, it wouldn't come up to normal temperature at all and you'd get a check engine light.

Jeremy
Since it is a crucial racing thermostat what would make it overheat then?
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Old 09-04-2008, 12:38 AM   #12
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update: i tried burping the system and refilling it. the top hose and radiator cap weren't hot because the coolant in the system was so low despite the overflow tank being full. i went and drove ti around and let it idle for awhile and discovered the coolant is coming out of the overflow tank. since it is very erratic i don't think it's the thermostat, so would this be a water pump issue or possibly the head gasket that linsavy suggested?

Last edited by ssslagle6006; 09-04-2008 at 12:47 AM.
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Old 09-04-2008, 02:44 PM   #13
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If you have coolant coming out of the overflow then that is a pretty good indication of a headgasket leak.
You should be able to get all the air out of the system so that you get some flow. Only after some driving would you get another air pocket. Get a funnel and stick it in the rad filler. Fill it up high so that when you burp it is the highest point. Look for lots of small bubbles coming out of the funnel when you rev the engine when it is hot.
I also think you need to get it to a mechanic really soon before you toast your bearings.
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Old 09-12-2008, 12:15 PM   #14
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Update: Car went to Subaru of Plano. They said it was just an air pocket and did the 90,000 miles service and told me it was fine. Picked the car up Wednesday. Today it started overheating and leaking coolant from the overflow tank again. From everything I've read on here it makes me thinks it's a small headgasket leak. Does that sound right?
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Old 09-12-2008, 12:52 PM   #15
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Quote:
Originally Posted by Crucial Racing View Post
, crank the heater to run coolant through the heater core to get any air out that could be in that part of the system and add more water if necessary.
Jeremy
coolant always runs through the heater core.

There isn't a separate heater control valve in any Subaru
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Old 09-12-2008, 12:54 PM   #16
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Quote:
Originally Posted by ssslagle6006 View Post
Update: Car went to Subaru of Plano. They said it was just an air pocket and did the 90,000 miles service and told me it was fine. Picked the car up Wednesday. Today it started overheating and leaking coolant from the overflow tank again. From everything I've read on here it makes me thinks it's a small headgasket leak. Does that sound right?
try changing out the rad cap on the coolant tank for a new one. OR what the dealer SHOULD have done was test the car for a HG leak. ie: either coolant exhaust test or oil.
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Old 09-13-2008, 11:04 AM   #17
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did they actually pressure test the cooling system? That would tell you if there was indeed a leak somewhere. Then, if they found a leak and couldn't find it anywhere, they could run the tests sideways suggests (e.g., look for oil in the coolant or coolant in the oil)
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Old 09-13-2008, 02:16 PM   #18
ssslagle6006
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they said they tested the system and that air must have been sucked in when coolant was being added
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Old 09-20-2008, 12:35 AM   #19
ssslagle6006
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so after having my car a whole week they said it was fine and gave it back to me. an hour later it was overheating with coolant coming out the overflow. turns out they never drove it very hard when test driving it to try and replicate my problem. it now seems that it only overheats if the turbo is in use for an extended duration such as a spirited 45 mile drive home from the dealership. advice? it's going back to SoP tomorrow.
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Old 09-20-2008, 11:31 AM   #20
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Quote:
Originally Posted by sidewayz View Post
coolant always runs through the heater core.

There isn't a separate heater control valve in any Subaru

turning on the heater would probably actually make it take longer, as you are dumping heat overboard instead of heating up the coolant system. just doublechecked the manual, it makes no mention of turning on the heater.
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Old 09-22-2008, 11:36 PM   #21
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bump.
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Old 09-27-2008, 11:02 AM   #22
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any updates?
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Old 09-27-2008, 02:28 PM   #23
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When are you going to have the headgasket probability checked? Your symptoms support that conclusion, and you haven't checked it according to the info here.
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Old 01-10-2009, 09:49 PM   #24
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I'm having the P0483 CEL. Will try this and see if it works. BTW, my car is running fine and it's NOT overheating.
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