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Overheated after a long drive?


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25 replies to this topic

#1 BSOD2600

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Posted 01 October 2006 - 07:10 PM

Got a 94 turbo legacy wagon. I just got back from a 215 mi drive and when I pulled into the gas station (right off the freeway), coolant started to spew out the overflow. Then I continued home and the temp gage was about at 3/4, which is a LOT higher than I've ever seen it. A few minutes later, I get home and coolant is still spewing / bubbling out the overflow.

I just did this 215 mi drive on Friday with zero problems. Any idea why this is happening?

#2 Manarius

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Posted 01 October 2006 - 07:27 PM

Air pocket in the system? Poor performing cooling system? Might be time to flush out that system and put in some new coolant.

#3 BSOD2600

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Posted 01 October 2006 - 07:55 PM

Ok, but why all of a sudden would this problem pop up? I've done several long road trips in the past 2 weeks and never had a problem. I used one of those coolant/antifreeze measuring devices and it's fine. Also, since it's been an hour since I got back, the coolant overflow tank is now dry -- I assume the engine sucked the remainder back in? That mean I should go get some more coolant and add it to the system?

#4 ericem

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Posted 01 October 2006 - 07:58 PM

Ok, but why all of a sudden would this problem pop up? I've done several long road trips in the past 2 weeks and never had a problem. I used one of those coolant/antifreeze measuring devices and it's fine. Also, since it's been an hour since I got back, the coolant overflow tank is now dry -- I assume the engine sucked the remainder back in? That mean I should go get some more coolant and add it to the system?


i dont know stuff just happens like with my subaru legacy, 9k CDN later

#5 The Dude

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Posted 01 October 2006 - 08:01 PM

Thermostat failure could be a possible cause. Also check the cooling fans. A defective radiator cap is another possible problem item. Whatever you do handle the problem quickly, because an all aluminum engine takes overheating extremely poorly.

#6 BSOD2600

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Posted 01 October 2006 - 08:19 PM

How does one test the thermostat?

The fans operate fine.

What could be defective about the radiator cap? Nothing seems to be leaking out of that...

#7 ericem

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Posted 01 October 2006 - 09:22 PM

How does one test the thermostat?

The fans operate fine.

What could be defective about the radiator cap? Nothing seems to be leaking out of that...


well sometimes the seals on thee rad cap create a airleak.. now the thermo stat is a unlikely problem because they usually make the engine not warm up when there jammed. I suggest u try a rad flush and nea rad cap.

#8 The Dude

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Posted 01 October 2006 - 09:36 PM

well sometimes the seals on thee rad cap create a airleak.. now the thermo stat is a unlikely problem because they usually make the engine not warm up when there jammed. I suggest u try a rad flush and nea rad cap.


No, when the radiator cap fails to seal it can not pressurize the cooling system. Pressure RAISES the boiling point of the coolant. No again, thermostats can, and often do, fail in the OPEN or CLOSED position. If the thermostat fails in the closed position the coolant in the engine block will not be able to circulate to the radiator and will overheat.

It is possible to test a thermostat by heating it to its' operating temperature. However, it necessary to remove the thermostat from the car in order to test it. Given the fact that the thermostat is already out, and a replacement is fairly cheap, most people just replace them without testing. If you replace the thermostat be sure to use a genuine Subaru brand thermostat. After market thermostats usually do NOT work well in Subarus.

#9 Virrdog

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Posted 02 October 2006 - 08:49 AM

Aftermarket Vs. OEM

Posted Image

Any questions?

#10 porcupine73

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Posted 02 October 2006 - 11:37 AM

Any questions?

Yes, are those for the same vehicle? Just kidding. Yes the OE looks like the Binford and the other looks, well, not so big. Anywho, make sure to get a new gasket with the thermostat (that rubber thing around it), my new OE didn't come with one but the parts dealer reminded me.

#11 BSOD2600

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Posted 02 October 2006 - 02:17 PM

I checked the coolant tank this morning and the sucker is dry. Going to buy some coolant this afternoon after classes. Obviously the green antifreeze is ok to put in -- what about the clear 'universal' stuff NAPA sells? After I fill it up, hopefully this overheating thing was a one time deal...

I'm still failing to understand how the radiator/coolant cap could be leaking. If it's under pressure from the system/heat, I'd expect some coolant to be leaking out; which I don't see.

#12 grossgary

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Posted 02 October 2006 - 02:22 PM

radiator cap and thermostat are cheap and easy to replace so it's nice to rule them out right away and not risk further overheats for something simple.

for your instance, i'd say the cap sounds like it's doing it's job. any more problems after your refill and i'd replace the thermostat.

radiator, water pump then head gaskets is where we're going to go after that.

#13 ericem

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Posted 02 October 2006 - 03:16 PM

radiator cap and thermostat are cheap and easy to replace so it's nice to rule them out right away and not risk further overheats for something simple.

for your instance, i'd say the cap sounds like it's doing it's job. any more problems after your refill and i'd replace the thermostat.

radiator, water pump then head gaskets is where we're going to go after that.


u know what are u sure ur waterpump isnt leaking? On my subaru my water pump dripped like a rain storm, got it replaced, and the leaking stopped all together.

#14 BSOD2600

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Posted 02 October 2006 - 03:55 PM

u know what are u sure ur waterpump isnt leaking? On my subaru my water pump dripped like a rain storm, got it replaced, and the leaking stopped all together.


I'm quite sure. When I pulled into the gas station, I popped the hood and could see all the coolant bubbling out the overflow tank. Same with when I got home.

#15 Virrdog

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Posted 02 October 2006 - 04:03 PM

I'm quite sure. When I pulled into the gas station, I popped the hood and could see all the coolant bubbling out the overflow tank. Same with when I got home.

That would indicate the system has lost pressure (lower boiling temp). Have a Subaru familiar shop look at it. They should be able to find the leak in a minute or two just by looking at it.

#16 porcupine73

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Posted 02 October 2006 - 05:06 PM

If you aren't sure what type/brand antifreeze is in the system, before you add, you might want to drain it all and flush with water and then refill. Subaru specifies a phosphate, non-amine product, which is common of Japanese make coolants; I think a close match is G-05 (BASF licensed to Zerex I believe) and that's common in late model fords and some other vehicles. At the minimum if you mix coolant types I would change and flush it all out within a couple months. Color does not necessarily indicate coolant type.

#17 BSOD2600

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Posted 02 October 2006 - 05:54 PM

Ok, went and got more coolant and filled it up. Started the car and let it idle until the temp was in the normal range. Started to drive around the block and the temp gage climbed back up till it was overheating.

After I got back home, I felt the top hose that goes into the radiator -- it felt warm. The radiator and the bottom hose that goes into the water pump felt cold. Since I don't have a leak around the water pump nor any odd noises, I guess it's the thermostat thats bad?

Any tips to replacing it?

#18 porcupine73

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Posted 02 October 2006 - 06:31 PM

Based on those symptoms sounds like thermostat would be a good thing to look at. If it's not that, maybe radiator or something is plugged up, or for some reason water pump isn't working too good. Don't overheat the thing too many times or bad things will happen, hopefully they haven't already. If you crank the heater do you get nice hot air?

Not sure if '94 is anything like '96 but if it is thermostat is probably one of the easiest jobs you could ask for. Just (when cool of course) drain coolant (or not if you don't care about it dumping out like crazy), and remove the two bolts securing that plastic thing hooked to the end of the lower radiator hose and pull it down and the thermostat will either come out or be visible to be pulled out (it just goes into the bottom of the water pump).

#19 johnceggleston

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Posted 02 October 2006 - 08:22 PM

before i spent another nickle or any more time on the problem i'd have the coolant checked for hyrocarbons. this will tell you if you have a headgasket leak. if you do then you are wasting your time and money on other fixes. i'd go to a napa store or the like and ask about a test kit for exhaust in the collant.

hopefully it will not be there, but i've read a lot of threads that started as overheating fixes only to finish with headgasket fix. sure the t-stat is an easy cheap fix, but do a survey and ask how many people have actually replaced a t-stat and had that resolve their problem. my guess is the number will be low.

the only difference between an air lock/bubble in the collant system and an exhaust bubble / lock in the coolant is that no matter howmany times you burp the system to clear the air out of it, when it's an exhaust leak, it will keep coming back. you can put coolant in ti till the cows come home and it will just do it again.

get it tested first!!! then decide how to spend your repair dollars.

#20 BSOD2600

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Posted 02 October 2006 - 08:54 PM

Well I replaced the thermostat with a OEM subaru part... also got an aftermarket -- damn what a difference!

Aftermarket on the left and OEM on the right:
Posted Image

Anyways after getting the new one installed, I left the car idle for 5 minutes. After a while the fans kicked on but I still didn't feel the upper radiator hose getting warm. A few minutes later the temperature gage crept up past the 'normal' mark and sure enough the car was overheating again! Oddly enough this time the engine didn't suck/blow any coolant from the overflow.

Guess my water pump went bad? A new one from Subaru is $114, plus who knows how much for labor. The subaru dealer is 3.1 miles away from my house, think I should risk driving it there or get it towed? Also, I plan on having them do the hydrocarbon sniff test, just in case the engine is on its way out.

#21 ericem

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Posted 02 October 2006 - 08:58 PM

Well I replaced the thermostat with a OEM subaru part... also got an aftermarket -- damn what a difference!

Aftermarket on the left and OEM on the right:
Posted Image

Anyways after getting the new one installed, I left the car idle for 5 minutes. After a while the fans kicked on but I still didn't feel the upper radiator hose getting warm. A few minutes later the temperature gage crept up past the 'normal' mark and sure enough the car was overheating again! Oddly enough this time the engine didn't suck/blow any coolant from the overflow.

Guess my water pump went bad? A new one from Subaru is $114, plus who knows how much for labor. The subaru dealer is 3.1 miles away from my house, think I should risk driving it there or get it towed? Also, I plan on having them do the hydrocarbon sniff test, just in case the engine is on its way out.


drive it there, subaru will fix ur car then everything will be alright. Just be sure to pull over every so often. Not worth the money to tow it.

#22 BSOD2600

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Posted 02 October 2006 - 09:11 PM

drive it there, subaru will fix ur car then everything will be alright. Just be sure to pull over every so often. Not worth the money to tow it.


I really don't want to warp the engine block or anything. Plus I've got towing on my USAA insurance.

#23 The Dude

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Posted 03 October 2006 - 08:36 AM

You're getting close to the end, but did you check the radiator for obstructions? After running the engine, the surface of the radiator should be uniformly warm with no hot or cold spots.
When was the water pump last changed? It's rare for a genuine Subaru water pump to fail under 100,000 miles.

#24 BSOD2600

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Posted 03 October 2006 - 01:30 PM

How exactly does one check the radiator for obstructions -- stick a hose to the top and see of water comes out the bottom?

Went out this morning and removed the coolant cap and heard a sucking sound. Noticed the coolant level dropped so I added more... a lot. Kept massaging the upper radiator hose and adding more coolant to the tank. Then started the car and let it run with the cap off. The level slowly went down. Eventually when the engine reached the normal operating temperature, coolant started to continuously come out. I decided to then put the cap back on. Sure enough, more slowly this time, the temperature crept up back to overheating. This time though, the upper radiator hose was hot, while the lower was still cold.

Turned the car off and then took off the smaller hose that goes from the coolant tank to the upper radiator area (right above the large radiator hose). Soon as I took it off, a lot of air/steam came out. Let the car cool down for 10 min and then put coolant in that small tube. It didn't take much before it wouldn't really drain down any more water.

I left the small tube disconnected and up in the air. Turned the car back on and let it warm up. Steam kept coming out the smaller tube. Once again the car slowly got to the overheating temp and I turned it back off.

I've got a CEL that I need to find out. Also once it cools down, I plan on taking off the large upper radiator hose and see if there is any coolant in the radiator -- if not, filling it up. If all of that doesn't work, then I guess it's off to Subaru I go... *sigh*.

#25 BSOD2600

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Posted 03 October 2006 - 04:58 PM

More news...

An hour after my last post, I went out and started messing around again. Right away I noticed the coolant overflow tank was dry! Yay, that means the engine sucked all the coolant in there up. I started up the car again with the coolant cap off and let it warm up. Once it reached the normal temp range, coolant started to come out the coolant tank on top. I capped it and let it idle for a while longer. Temps seemed to be ok. Went for a drive around a few blocks and the temp stayed normal. YAY!

Drove back home and let it idle some more in the driveway. Then the temp started to climb back up to the overheating point. Turned it off and let it sit for 2 hours. Came back and put more coolant into the top coolant tank and did an errand on the way to school -- the temp stayed normal.

So I guess, there was a giant amount of air in the system which caused the coolant not to flow properly? I plan on checking the coolant levels every day the rest of the week to continue to get rid of all the air.




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