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Strange Overheating Problem


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10 replies to this topic

#1 phoenix1125

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Posted 13 April 2005 - 05:55 PM

My wife and I just made our first car purchase: a '98 Outback. We love the car, but recently started having trouble with it overheating. The problem started after we drove to the beach for an oyster barbeque: the roads were hilly and winding and I was driving faster than usual because we were running late. Anyway, when we arrived at the beach after driving for ~2 hours, we noticed that the engine was smelling a little. And when we left the beach some 8 hours later, the car quickly overheated after driving for about 15 minutes. At this point, the resevoir was full but not overflowing, and I noticed that it was thicker with coolant than usual. I also noticed steam rising from the area directly beneath the radiator cap. After the car cooled down, it took about one gallon of water to fill up the radiator and resevoir again. Once we did, we were able to drive home without overheating.

I took the car to my mechanic, whom I believe to be good & trustworthy, but he doesn't specialize in Subarus. He replaced the thermostat and radiator cap and pressure-tested the system, but didn't find any leaks. He also checked the coolant for signs of oil and the oil for signs of coolant but didn't find any. And I haven't observed any bubbles in the coolant. I was hoping that it might just have been the radiator cap leaking, but the following weekend I took the car on a long drive in hot weather and, after 3-4 hours of normal functioning, it overheated again.

It seems like it is functioning normally until it loses a certain amount of fluid, and then overheats. My mechanic thinks it might be that the radiator is partially clogged, but if that were true then I would expect the fluid to be overflowing from the resevoir. Is there any chance that the problem could be due to a loose or punctured resevoir hose? The hose feels somewhat loose/slippery where it meets the radiator, and there seems to be signs of radiator fluid/corrosion below that point (directly below the radiator cap; also where I observed the steam rising). Is there any way I could test to see if this is the problem? Are there any other ways the system might be leaking which wouldn't show up in a pressure test?

Also, I'm looking for instructions regarding how to "burp" the system. I tried searching the archives but didn't find anything; if you have any advice to offer or know of any good links, I would be much obliged. Thanks in advance for your time and assistance.

#2 brus brother

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Posted 13 April 2005 - 06:49 PM

Did you buy from a dealer?
This model is notorious for head gasket leaks. Apparently there is a hydrocarbon sniff test that can be performed on the coolant which may be more diagnostic than looking for oil in the reservoir.
The burping issue is mentioned many times on this site. Use the USMB search function in the bars at the top of the page.
I hope it turns out to be as innocuous as trapped air or a blocked radiator.

#3 Gnuman

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Posted 13 April 2005 - 10:17 PM

My wife and I just made our first car purchase: a '98 Outback. We love the car, but recently started having trouble with it overheating. The problem started after we drove to the beach for an oyster barbeque: the roads were hilly and winding and I was driving faster than usual because we were running late. Anyway, when we arrived at the beach after driving for ~2 hours, we noticed that the engine was smelling a little. And when we left the beach some 8 hours later, the car quickly overheated after driving for about 15 minutes. At this point, the resevoir was full but not overflowing, and I noticed that it was thicker with coolant than usual. I also noticed steam rising from the area directly beneath the radiator cap. After the car cooled down, it took about one gallon of water to fill up the radiator and resevoir again. Once we did, we were able to drive home without overheating.

I took the car to my mechanic, whom I believe to be good & trustworthy, but he doesn't specialize in Subarus. He replaced the thermostat and radiator cap and pressure-tested the system, but didn't find any leaks. He also checked the coolant for signs of oil and the oil for signs of coolant but didn't find any. And I haven't observed any bubbles in the coolant. I was hoping that it might just have been the radiator cap leaking, but the following weekend I took the car on a long drive in hot weather and, after 3-4 hours of normal functioning, it overheated again.

It seems like it is functioning normally until it loses a certain amount of fluid, and then overheats. My mechanic thinks it might be that the radiator is partially clogged, but if that were true then I would expect the fluid to be overflowing from the resevoir. Is there any chance that the problem could be due to a loose or punctured resevoir hose? The hose feels somewhat loose/slippery where it meets the radiator, and there seems to be signs of radiator fluid/corrosion below that point (directly below the radiator cap; also where I observed the steam rising). Is there any way I could test to see if this is the problem? Are there any other ways the system might be leaking which wouldn't show up in a pressure test?

Also, I'm looking for instructions regarding how to "burp" the system. I tried searching the archives but didn't find anything; if you have any advice to offer or know of any good links, I would be much obliged. Thanks in advance for your time and assistance.


phoenix1125, first off I live about 50 miles from you. My recomendation is to flush the coolant from the system and check the radiator for flow (also for cracks around the cap area, where you saw steam and the hose was wet/slippery). Shoot me a PM if you want directions to my place and I can help you burp the system. After you see it for the first time, you will be able to do it yourself easily.

#4 Setright

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Posted 14 April 2005 - 12:30 AM

Well, head gaskets are the weak link in this car, and your symptoms do point in that direction. Of course a proper flush and re-fill (Gnuman to the rescue!) would be a good place to start.

#5 phoenix1125

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Posted 14 April 2005 - 08:16 PM

Thanks for the helpful responses; I'm new to USMB & really appreciate the warm welcome and good information. After reading a bunch of posts yesterday, I took a look at the radiator and found the bleeder plug -- and found that it was snapped at the neck and leaking fluid. This would explain the fluid loss and air pockets, but I don't understand how it could have passed the pressure test (& how my mechanic failed to notice it). Maybe it was the radiator cap at first, and then they accidentally snapped the bleeder plug when putting it back in? Still, I don't see how they could have snapped the plug without noticing it... As an aside, is $300 about right for "rodding" a radiator (or whatever it's called)? I just want to cross-check my mechanic's prices.

Anyway, I bought a new bleeder plug and also an OEM thermostat & gasket (my mechanic installed a Stant), so this will be my first (hopefully minor) repair. With regard to burping the engine, this is what I've gathered: park the car with the front uphill, let the engine cool down (pref. overnight), open the radiator cap & bleeder plug, start the engine & blast the heater, keep adding 50/50 water/coolant until full, maybe bounce on the bumper a little, stop the engine when the thermostat opens & the coolant starts overflowing, then top off & replace radiator cap & bleeder plug. Does that sound about right? With regard to changing the thermostat, I'm planning on following the Haynes manual, but is there anything I should watch out for? From the posts, it sounds relatively straightforward...

Gnuman, thank you very much for the generous offer; I may take you up on it if I can't figure it out how to do it on my own. Thanks again to all!

~Chris

#6 Setright

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Posted 15 April 2005 - 12:57 AM

Bleeding: The secret is to fill the engine with coolant through the top radiator hose. Do a site search for "coolant replacement", you'll find my detailed description of the whole procedure.

Thermostat: Clean the mating surfaces to avoid leaks, and use a new gasket. Those tiny bolts and the aluminium water pump can't handle much torque, so be careful when tightening them. Give the threads some copper grease if you plan on removing the thermostat again some day.:)

#7 phoenix1125

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Posted 15 April 2005 - 04:21 PM

Well, I replaced the bleeder plug and it turns out that it was only a secondary problem: the car is still overheating. What seems to be happening is this: when the engine is under a heavy load, like when it is driving up steep hills, the radiator seems to be pushing fluid out of the resevoir tank (I saw evidence of this last night when I took it for a test drive). However, since replacing the bleeder plug, the radiator now sucks back coolant from the resevoir (just like it did the first time). Therefore, I suspect that my mechanic either broke the bleeder plug after pressure-testing the system or that it broke on its own shortly thereafter.

My mechanic was suggesting that this behaviour could be caused by a clogged radiator; could this be the problem? If so, would you recommend buying an OEM radiator or are there any less-expensive (but still high-quality) aftermarket radiators you'd recommend?

Are these symptoms still consistent with an HG leak? Specifically, I'm thinking about the fact that the radiator passed the pressure test and that it is sucking coolant from the resevoir tank. Anyway, I'm planning on buying a kit to test for hydrocarbons in the coolant; are there any other good tests you would recommend? Finally, if the symptoms are consistent with either a clogged radiator or an HG leak, which one seems to be the more likely culprit? Should I replace both parts or just start with one?

Setright, thanks for your help: I found that post you wrote about changing the coolant & also a lot of other good advice of yours on the boards. :)

Cheers,
Chris

#8 Cougar

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Posted 15 April 2005 - 04:43 PM

I would get a block check done. This will tell you if there is a HG leak more than a coolant pressure test. Your problem does appear to be a HG leak.

#9 Setright

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Posted 17 April 2005 - 12:09 AM

Yes, your symptoms are those a small HG leak. Compression gases are being pumped into the coolant and causing sudden vapour lock in the water pump. This leaves no trace of oil in the coolant.

My EJ22 behaved EXACTLY like your engine and I spent a lot of time and money replacing lots of other things before I did the HG's. Don't waste yours, replace the HG's.

(And thanks for the praise :) )

#10 mutant_dan

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Posted 18 April 2005 - 11:07 AM

Yes, your symptoms are those a small HG leak. Compression gases are being pumped into the coolant and causing sudden vapour lock in the water pump. This leaves no trace of oil in the coolant.

My EJ22 behaved EXACTLY like your engine and I spent a lot of time and money replacing lots of other things before I did the HG's. Don't waste yours, replace the HG's.

(And thanks for the praise :) )


Mine did the exact same thing as well. The hydrocarbon tests didn't show anything. I replaced the entire cooling system hoping that I could avoid the HG. Have the cylinders pressure tested and I would be willing to bet you have a leak.

Find a good Scooby mechanic to service your car. There is a Subaru Only or Strictly Subaru type mechanic in Oakland. I don't specifically remember the name. I like to stay away from the dealer, but that is just me...

#11 cookie

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Posted 18 April 2005 - 11:41 AM

They don't always show up on a hydrocarbon test, compression tests can't find them until they are really blown, and a leakdown test is iffy until they leak when cool.
If it were my car I would change them at this point.




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