Overheating.... Thermostat or Head Gaskets?

[mikeamondo]

Can't believe my luck.... our 03 is sitting with a smushed snoot, and now my daughter's 95 legacy is overheating..... 2.2L AWD auto, 90k miles.

 

About a week ago, she noticed some coolant on the ground, and I took a look see.... added 1/2 gallon or so and ran the car till it got warm, looking for leaks.... found none. I think now that it may have overflowed when she got home the previous evening, rather than slowing leaking overnight.

 

Today, she drove it about 5 miles and then noticed the temp guage pegged at H. She pulled off and I came out to check it.... the overflow jug is filled to the top, and 1/2 hour after shutting it down (when I got there), the radiator cap was cool and could be removed. She also said she tried to cool the engine by running the heater, like I had told her to do if it ever ran hot.... Good Girl, Maisie!.... but only cold air came out.... no heat.

 

The engine was cool, so I had her drive about 3 miles to our mechanic's shop... closed today, Sunday.... she said it registered normal until coming up a steep, fairly long hill, (Easton Hill for you Morgantown folk), when it shot up to H. On the level again, it dropped back a little, but still almost to H.

 

I'm heading back into town, going to move the car to my office where there is a garage, and go buy a new thermostat to try.... I'll check back here before I dig in to see if any of you have any advice. Once I drive across town, I'll check the upper hose to see if it's hot... I understand that would indicate thermostat stuck closed.

[GeneralDisorder]

You can *try* replacing the radiator cap - that's about the only thing that would allow it to throw all the coolant into the overflow bottle if it were bad other than the head gaskets.

 

But I hate to tell you - that's almost a sure sign of head gasket failure. You can probably borrow a bit of time by punching the guts out of the thermostat and driving it without one. Also leaving the radiator cap loose or buying a lev-r-vent cap and leaving it open..... that will vent the exhaust gasses that are pushing the coolant into the overflow bottle and allow it to be driven at least.

 

What's happening is exhaust gasses are leaking into the cooling system from the head gaskets - that causes the system to go over it's intended operating pressure of 13 PSIG - the radiator cap opens and the exhaust gas escapes and takes a quantitiy of coolant with it. Over time that results in a loss of coolant - it's volume being replaced by exhaust gasses. There is a tipping point in the system where enough coolant has been lost that the water pump can no longer circulate coolant through the block - it just can't push it past the exhaust gas bubble - that's when the gauge spikes and you pull over - finding the overflow bottle full and with bubbles in it. After it cools it sucks all the coolant back into the system and drives normally again till the cycle repeats.

 

This is very common with the 2.5's of simlar vintage but I've seen a few EJ22's do it as well - when the gaskets blow they seem to blow the same way as the EJ25D's but it just happens very rarely on the 22's.

 

Both hoses should be hot when running and the thermostat open. Though I have seen situations where bad head gaskets would cause overheating quickly enough that the thermostat didn't open - resulting in an overheated engine and a cold lower hose.... sounds weird I know but I've seen it.

 

The fact that it was driven for a week after the first overheat would seem to point to a bad radiator cap as a possible culprit..... but then again the overheating could have damaged the head gaskets as well so it's really hard to say at this point.

 

GD

Edited November 14, 2010 by GeneralDisorder

[idosubaru]

you could still have a leak or clogged radiator, you'll need to investigate further. if they overheat the coolant will boil over into the overflow reservoir.

 

so - you're going to want to properly fill and burp this thing and make sure it's not loosing coolant or overheating due to the radiator.

 

i have a car right now that was boiling the coolant into the overflow reservoir. new radiator, it's fine now.

[GeneralDisorder]

Yeah - if the radiator is bad it could be overheating - how does the coolant look? And how does the radiator look? I know in some parts of the country the radiators look about as good as the wheel wells by that age .

 

GD

[mikeamondo]

It's not boiling over.... no bubbles, etc. And, it never gets sucked back into the engine.... as though once it came out and filled the bottle, it could not get back in.

 

Just now, I drove the car about 7 miles, part of it interstate. Had to pull over once and let it cool down, after it pegged H. It heated up like you would expect, but kept on going into the Hot range. When I got to my office, I popped the hood...

 

All the fluid was still in the bottle, and it was cold. I could stick my finger in it. The top hose was hot to the touch. The bottom hose was cold. The fans were not running, and it seemed to me they should have been.

 

So, what does that tell you?

[GeneralDisorder]

Pull the radiator and thermostat - flush the radiator and look inside with a flashlight and see what it looks like.

 

If it's not a clogged radiator or bad cap then it's head gaskets.

 

An exhaust gas bubble will displace the coolant - even cold coolant - due to the increased pressure in the system. That same bubble will cause the engine to overheat and yet the fans won't come on due to a weird fluke in the way the temp probes are setup - the ECU probe doesn't see the temp change the same way as the gauge probe does so when the coolant level drops the gauge pegs and the ECU doesn't see the change and doesn't kick the fans on.

 

*something* is displacing the coolant - and usually that's from either severe overheating, or from exhaust gasses taking the place of the coolant. Coolant expands when hot but the fact that you have cold coolant in the overflow bottle doesn't lend credance to that argument.....

 

You are going to have to do some investigating. But it sounds like a HG problem to me - 7 miles on the interstate shouldn't overheat the engine even with a partially clogged radiator due to the massive airflow at those speeds - does the coolant look like mud? If it's clean and green then that's probably not the issue.

 

GD

[idosubaru]

when it's running do you see bubbles coming into the overflow tank? in general constant bubbles are bad and signal likely headgaskets - though a really hot coolant will boil and have "bubbling" too of sorts.

 

i and someone else just replaced a radiator this summer in EJ vehicles as new as 2000. i was just kind of winging it and couldn't verify the radiator with any test. i found one for like $67 new though so figured why bother wasting time testing it for such a cheap price.

 

two symptoms i had:

 

1. if i shut the car off and coasted for a bit (down a hill), then turned it back one, it would temporarily cool back down. that was the only way, turning the heat on wouldn't help.

 

2. with the bottom hose removed and a hose running to the cap, it would not flow all the water. it would flow some, maybe %50, but not all of it. a radiator in my garage would flow all of it.

 

i would suspect symptoms could vary based on how it's clogged, or water pressure of your hose.

 

not sure what style yours has but i have a couple used legacy/impreza radiators that i could let you borrow or try out. i have a legacy manual trans and impreza auto trans i think.

[mikeamondo]

Swapped the thermostat... started the car and as it ran, filled the radiator, with the air bleed plug at the top open.... when steam started coming out of the plug, I put it back in and continued to fill the radiator till full.... Idled for 20 miniutes or so and temp gauge came up half way and stopped. Fans came on and ran fine. Thought I had it fixed.

 

Headed up the road for test.... as I accelerated, the needle began climbing right away and continued steadily up to hot.... less than a mile down the road. Came back and shut it down.

 

No muddy or dark color to the fluid... nice and green. I've never seen any bubbles anywhere. The jug is just full of nice, green, cold fluid. In this last test, the lower hose never did get hot....

 

Plugged radiator?

[GeneralDisorder]

Maybe - remove the radiator and inspect as I noted above. Put a garden hose in one end and see how quickly it flows out the other side. If you only have a trickle then it's plugged.

 

Where is all this corrosion? It would be evident in the coolant - it would be full of crap if there was enough in there to plug up the radiator. I've drained muddy, brown coolant from a couple Subaru's and had them run fine afterward - so it would take a LOT to plug one. I highly doubt that's the problem or you would have seen evidence of it when changing the t-stat. Consider for a moment that virtually the entire cooling system is composed of aluminium - the engine block and heads, the radaitor, and the heater core are all nearly 100% aluminium and plastic. What is there to corrode and plug stuff up? There just isn't the neccesary components for that level of contamination. Usually EJ's are very clean from a cooling system standpoint. I rarely see anything but nice green coolant and I have yet to encounter a plugged EJ radiator - cracked plastic end tanks is what I typically see.

 

I say it's head gaskets - I've seen that behavior before and I've tried installing new radiators, thermostats, etc and it didn't help. Pulled the heads and found the problem.

 

GD

Edited November 15, 2010 by GeneralDisorder

[idosubaru]

Mine was so hard to tell, it was kind of annoying because i didn't want to guess. The water hose test, the infrared temp gun was inconclusive to me....nothing set it apart for certain.

 

I think the most convincing thing was how consistent it was. It would do the exact same thing every single time...i just knew it was going to overheat, when, and how long it'd take. Using A/C or driving up hills or accelerating just made it happen faster. and hotter days it'd happen quicker than colder days (like at night). i've never seen EJ headgaskets be that predictable....not saying it's not possible but all the EJ headgaskets i've seen have been more variable.

 

still a very unquantitative measure and i was never fully convinced until the new rad solved it.

[the_bard]

For once, I've got something to offer, instead of just lurking .

 

I toasted a 2.5L in my '97 OBW under warranty, since the dealer I bought it from was convinced it wasn't a clogged radiator. When I say toasted, I mean burned. Overheated. Warped. Killed 'til dead. Over a two and a half month period, it'd overheat. The dealer claimed to have swapped one headgasket, water pump, thermostat, etc., prior to my having bought it. Every time I brought it back in, saying it was overheating again, he'd claim he couldn't replicate it. Like grossgary, it wouldn't act up all the time... stressing it by running up a good grade at highway speed wouldn't cause it to oveheat, but running on a flat grade at 40 would. Other days, the reverse would occur. Eventually, it died.

 

I limped it over to him (CEL flashing, blowing oil out the back), and he took a month to swap in a '95 2.2L. After that, I never bothered bringing it back in, and just dealt with it myself. It began overheating as I was pulling it back into my apartment's parking lot.

 

I never saw any sediment in the coolant. But when I pulled the radiator, drained it, and filled it upside down... I got a chunk of calcium (I assume) the size of my thumb falling out of the top. Several smaller chunks came out, too. I swapped the radiator, and haven't had a cooling problem since.

 

So I'd also recommend checking the flow through the radiator... it's better than simply replacing part after part (or in my case, having the dealer swap engine after engine...:-\ )

[mikeamondo]

Yesterday was a long day.... just realized I forgot one symptom. After I drove the car with the new thermostat and it overheated, I noticed it was leaking from under the cap, kind of in small surges. Does that mean a bad cap? And could that account for the symptoms? Could you give me a description of the function of the cap itself and how it relates to the system as a whole?

 

Also....

1. if i shut the car off and coasted for a bit (down a hill), then turned it back one, it would temporarily cool back down. that was the only way, turning the heat on wouldn't help.

 

2. with the bottom hose removed and a hose running to the cap, it would not flow all the water. it would flow some, maybe %50, but not all of it. a radiator in my garage would flow all of it.

 

 

Number 1 fits exactly with my car. And it's completely predictable like you describe. No bubbles that I've ever seen. It sounds like number 2 test can be performed with the radiator in the car..... is that right? If so I might try that this afternoon, before giving in and taking it to my mechanic....

 

Thanks!

Mike

[mdjdc]

I don't think you filled her properly. You said that you started the car and then filled her until there was steam coming out of the vent cap. You need to fill the car when it is not running. Put her on an incline with the nose up. Take out the vent cap and fill her until you antifreeze coming out of the vent, then replace the vent and start the car. Continue replacing fuid as it goes down and the thermostat finally opens up. Then you ar full. Put a new cap on her. They are cheap and then take her for a drive. If she overheats, check the flow of the rad, but they rerely go bad. My feeling is, that if she continues to overheat, you need to doa headgasket job. Don't keep running her as you will run the risk of damaging the rod bearings.

[davebugs]

Drain, then fill through the top radiator hose, reconnect it, then fill the radiator. Then start the car and continue.

 

If I have a car that's a problem I often pull it up on rhino ramps to get a little elevation to the front.

[mikeamondo]

SUCCESS! Backed the rear end over a small bank (snoot high) and removed the upper hose, filled the block from there and put the hose back on. Then filled the radiator with the air bleed plug out and started the car. Added a little more while he idled and then closed up everything. New I was on the right track, as the lower hose finally got warm. Took it for drive... about 5 miles... .up a steep hill and back... stayed cool the whole way!

 

Where's that dancing banana?!?! There he is! Dance, Banana, Dance!

 

Looks like it was a bad cap that led to low fluid and an air bubble. Sure beats head gaskets! Thanks for all the help!

 

--Mike

[vasy]

Drain, then fill through the top radiator hose, reconnect it, then fill the radiator.

 

This is how I fill the system: after draining, remove the vent plug on the top right side of the radiator. Find the smallest funnel you can get and attach a very small tubing to the funnel. Insert that tubing into the vent hole towards the top radiator hose until the end of the tubing is in the top hose. With the radiator cap off, pour coolant very slowly into the funnel until it shows up in the radiator cap opening. Do this with the front end of the car raised or on an incline. Replace the vent plug but do not over-tighten. If you damage it, about $15 to replace. This way you don't need to disconnect the hose - without any chance of over-tightening the hose clamp to damage the radiator neck. But it'll take more time to fill up because the funnel and the tubing must be small to fit into the vent hole.