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Old 11-27-2011, 08:20 PM   #1 (permalink)
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Default 1999 Outback intermittent overheating

Hello,
I have a 1999 Outback just replaced the head gasket on drivers side. No oil residue or exhaust smell any more in coolant overflow bottle. Replaced thermostat, timing belt, cleaned MAF sensor. Car runs fine for 5 to 20 minutes then temp climbs and pegs at hottest setting. I hear a screech like a belt loose, and have compression/power loss. Sometimes temp stays hot and bubbles out overflow bottle....sometimes it drops rapidly to normal, stays for 10 minutes, and climbs again. I backfilled the upper hose, and bled the antifreeze at the radiator bleed valve when warmed up, although I did not do this on an incline or raise the front of the car. Heater blows hot, can't see any leakage at waterpump weep holes. Check engine light is on with codes P0106, P0325, P0507, P1507. Rather than just replacing the knock sensor and idle air control, I wonder if anyone can help me get a handle on it all.
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Old 11-27-2011, 08:53 PM   #2 (permalink)
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Many Gen-1 OBs, including mine, have a clogged radiator after a HG failure that can lead to overheating. The combination of hot exhaust gases and coolant can form a white pasty substance that clogs up the narrow passages. I pulled my rad and took it to a radiator shop where they did a flow test on it for $20 ... then I bought a new one ... overheating problem solved.

I'd get a handle on the overheating problem before worrying about the codes if there is no driveability issue.

EDIT: I must be getting tired to forget this the first time, but did you use a genuine Subaru thermostat? They really are different than aftermarket ones and seem to work much better in our cars ... highly recommended. A new radiator cap can sometimes work a miracle, too.
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Old 11-27-2011, 09:04 PM   #3 (permalink)
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Well firstly the compression/ power loss is because the engine is at max temperature which is not good at all. When you replaced the thermostat did you use a genuine Subaru part or was it an aftermarket one?......these engines just do not function well with aftermarket t/stats(I have no idea why). From experience I would say you still have some kind of head gasket issue. The bubbling of coolant into the overflow is a classic sign and the fact that it is "intermittent" is another classic telltale sign. Who was it that diagnosed a single head gasket and why were both heads not done? As RobLog said it could be the rad, and that would be a good first step. And yes you should be worrying more about the overheating than the codes.
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Old 11-27-2011, 09:59 PM   #4 (permalink)
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Thanks RobLog, I did not use a Subaru thermostat, so I will get one tomorrow and replace, as well as a new cap. If I still get the problem I will pull radiator and have it pressure tested. Side note: I broke the head off the pressure relief valve...the screw is holding the fluid in nicely, just may make future adjustments tricky!
Hey jc54bv, Thank you for your input. I do have bubbling in the overflow tank, but no exhaust or oil with it. I thought a blown head gasket problem did not produce an intermittent overheating problem, just a constant overheating problem...but I am new to Subaru s so I may be wrong. Oh, I forgot to mention when my mechanic (not a Subaru mechanic) replaced the head gasket on the driver side only (because he said compression ratios were normal in left side) the head gasket had not failed...one valve in cyl. 4 was warped and cracked producing zero compression in that cylinder. The valves in cyl 4 were really shiney silver, which he said was probably due to high heat. The valves in cyl 3 were normal tan looking.
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Old 11-28-2011, 07:08 AM   #5 (permalink)
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Sounds like you have a good mechanic...but I am surprised he didn,t change both as at that stage he would have had all the timing covers/accessories off. The reason I suspect a further head gasket issue is that the bubbling of coolant into the overflow is usually combustion gases at very high pressure, being forced through the cooling system. They then escape through the easiest exit which is the overflow.
Unfortunately...unless you have a complete gasket failure, it tends to be an intermittent problem on these cars. There are hundreds of post for people replacing T/stats, radiators, and much more, in the hope it is something simple. 9/10 its the H/G.
I hope it is not in your case, but it is good to be prepared for the worst.
Best of luck, from a fellow 99 owner.
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Old 12-14-2011, 06:54 PM   #6 (permalink)
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An update for anyone looking into this issue: I replaced the thermostat with a Subaru one (definately a better part than aftermarket), replaced radiator cap. I still had bubbles in the overflow tank for a few days, but that went away after several engine cycles. I jacked up the front end and put the car on a slight incline to get any bubbles out of the radiator through the radiator vent screw on the passenger side radiator...and I had quite a lot of air in there. It has been 3 weeks now and no more overheating since the air is out of the engine. Moral of the story, (1) always use a Subaru thermostat...the aftermarket ones will not work (2)make sure you bleed out air from the radiator after filling it. Thanks to all for your help.
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Old 12-14-2011, 09:30 PM   #7 (permalink)
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Quote:
Moral of the story, (1) always use a Subaru thermostat...the aftermarket ones will not work (2)make sure you bleed out air from the radiator after filling it.
Good advice. Congrats on the fix.
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Old 12-15-2011, 12:30 AM   #8 (permalink)
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awesome, glad it worked out to a simple fix! these things can be a bear to bleed, i've had a few throw curve balls at me and while it can't be logically speaking it seems random. one will bleed easily, without hardly doing anything more than filling, another will be a pain.

Quote:
Originally Posted by shayes220 View Post
I thought a blown head gasket problem did not produce an intermittent overheating problem, just a constant overheating problem
not the case. there are multiple failures modes and these engines tend to have very specific failure modes.

EJ25D's randomly overheat every time.
Later EJ25's (like 2000+ OBW's) do not overheat because of the headgasket leak. (though they will eventually overheat if you let the coolant get low, but top it off and it won't overheat even with a failing headgasket).

Quote:
Originally Posted by shayes220 View Post
(because he said compression ratios were normal in left side) the head gasket had not failed.
compression tests are almost useless on an EJ25D. EJ25D's often pass a compression test when headgasket issues first appear because of the way they fail.

both headgaskets should be replaced. the problem is so prevalent there are websites devoted to the issue, this website even has a "headgasket" dedicated forum and headgasket log thread, and it's not much extra work to just replace the gasket while you're in there. while it's the next phase EJ25, Subaru came out with multiple headgasket revisions up until 2010 even, a coolant conditioner (stop leak), and had a 100,000 mile extended headgasket warranty on 2000-2002 EJ25's...they are prone to failure, i would take the opportunity to do both.

Quote:
Originally Posted by shayes220 View Post
the aftermarket ones will not work
aftermarket tstats work, it's not that 100% of them fail, OEM is just higher quality and has lower failure rates.
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Old 12-15-2011, 02:19 AM   #9 (permalink)
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My trick for burping the radiator is to repeatedly squeeze the lower radiator hose. This will send air up and bring water down. I will do it over and over, constantly adding coolant, until the water level no longer drops. Also do it to the upper radiator hose.
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Old 03-07-2012, 03:20 AM   #10 (permalink)
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Originally Posted by grossgary View Post
awesome, glad it worked out to a simple fix! these things can be a bear to bleed, i've had a few throw curve balls at me and while it can't be logically speaking it seems random. one will bleed easily, without hardly doing anything more than filling, another will be a pain.

not the case. there are multiple failures modes and these engines tend to have very specific failure modes.

EJ25D's randomly overheat every time.
Later EJ25's (like 2000+ OBW's) do not overheat because of the headgasket leak. (though they will eventually overheat if you let the coolant get low, but top it off and it won't overheat even with a failing headgasket).

compression tests are almost useless on an EJ25D. EJ25D's often pass a compression test when headgasket issues first appear because of the way they fail.

both headgaskets should be replaced. the problem is so prevalent there are websites devoted to the issue, this website even has a "headgasket" dedicated forum and headgasket log thread, and it's not much extra work to just replace the gasket while you're in there. while it's the next phase EJ25, Subaru came out with multiple headgasket revisions up until 2010 even, a coolant conditioner (stop leak), and had a 100,000 mile extended headgasket warranty on 2000-2002 EJ25's...they are prone to failure, i would take the opportunity to do both.

aftermarket tstats work, it's not that 100% of them fail, OEM is just higher quality and has lower failure rates.
Not quite. I am posting this as a warning to all, because I just went through an ordeal with not one but two aftermaket thermostats--a Failsafe and a Duralast--and neither one worked.

Both caused overheating brand-new, upon installation, exactly as described in the original post and as blamed on the head gasket. Gutting one of the 'stats and replacing the empty housing with the gasket cured the overheating immediately, so it is the aftermarket 'stat, not the gasket.

With all the overheating, the lower radiator hose was COLD, meaning the POS aftermarket thermostat had not opened.

So, to anyone experiencing this type of overheating, try running with a hollowed out thermostat first, before you go and spend $$$, and if that cures the overheating, go get an original Subaru thermostat from the dealer and put that in.

Yes, only Subaru thermostats work in Subarus.
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