'90 Legacy overheating demons

[fj401968]

'90 Legacy 192,000 miles. Runs well. Doesn't appear to be using oil or coolant. I am not seeing visual signs of oil in my coolant. I've used a radiator flush product and back flushed the radiator as well. Nothing funky came out. I've replaced thermostat. Electric fan is working. Waterpump isn't leaking. Heater works fine so the heater core isn't clogged. Most days the temp is slightly below half on the gauge. If I head up over Teton pass the needle heads to the red in a hurry and I know it isn't just a faulty gauge because the engine runs pretty doggy too and I have to stop several times to let her cool down. I just noticed this a few mos ago.

 

Oddly, most days driving to work she's fine but some days out of the blue the temp will jump right up there. Now here's the funny part. If I stop and let the car idle the needle stays up there... however, if I give the motor a pretty solid 4.5k-5k rev the needle will instantly drop back to half. The occaisional overheating on flat land is seldom and random. Overheating while pulling my small cargo trailor is guaranteed now days especially if A/C is running. Running the heater does not seem to have much of an impact on the situation.

 

Initially I was suspecting a slightly blown headgasket that is introducing bubbles into the coolant and compromising the coolant's abilility to do its job since the thermostat and radiator seem to be doing their jobs. However, I'm not really seeing other signs of a blown headgasket... no white smoke and like I said, no real change in fluid levels, no sludge in oil etc... The engine runs fine. I've put several thousand miles on it since this problem surfaced expecting to see the problem worsen if it was indeed a head gasket issue. It hasn't though.

 

Is it possible the waterpump is slipping on the shaft or something? The serpentine belt is fairly new and properly adjusted so there is no slip there but I was wondering if it is possible for the impellor to be slipping somehow... is there a keyway that could be wore down and allowing the impellor to slip a bit on the shaft and to not work optimally which is why a rev of the engine has such a dramatic effect?

 

It would be a real bonus if I could eek another 50 or 60,000 miles out of this car but I really don't want to sink big money or time into it. This is my fourth Subaru and it's been a bit of a lemon. The transmission went out at 110,000. It cost me $1500. The tranny is starting to act a bit clunky again after 80,000 on the rebuild so I've been babying it. Also, the AWD got real sloppy and finally quite working about 30,000 miles ago so it is 2 WD now. Despite that, the car is comfortable... good A/C, cruise, moonroof, Alpine stereo, drives well and it has a new set of tires on it that I'd like to wear out. It gets me back and forth to work really well.

 

Any ideas??? Suggestions???

 

Thanks in advance!

 

Tracy

[drewd]

I had almost the same symptoms on my old Bronco...kept thinking it was a leaky HG, but it turned out to be an air pocket in the cooling system...sometimes the temp pegged high at idle out of the blue...soon as i hit the throttle it went right back down again. Took some time, but i got the air out and the temp doesn't get pegged anymore.

[fj401968]

Thanks for the reply... If I'm towing my small trailer on a hot day with A/C running or heading up over Teton Pass, revving the engine doesn't help. The needle creeps up into the hot range and stays there. Something is definately compromising the cooling system. What doesn't make sense is the consistency when under a load and the randomness of the problem when I'm running on flatland. Often weeks will go by with no problems then out of the blue the needle will climb to the hot zone in a hurry.

 

Tracy

 

I had almost the same symptoms on my old Bronco...kept thinking it was a leaky HG, but it turned out to be an air pocket in the cooling system...sometimes the temp pegged high at idle out of the blue...soon as i hit the throttle it went right back down again. Took some time, but i got the air out and the temp doesn't get pegged anymore.

[nipper]

I would say its one of three things, A- an air pocket, or B- a cloged radiator C- missing radiator fins. Radiator flushes over the counter dont really work all that well on a hige milage radiator. Also one other thing to consider. I had the same problem and decided it was time to replace the radiator. I ordered one of the net (www.radiator.com great people, they know cars). I pulled it out, and 30% of the cooling fins were gone. I could not see it because the AC was in front of the radiator. From the fan side the radiator looked fine.

 

 

nipper

[fj401968]

So am I to assume the water pump is an all or nothing item? It either works or not? Second, is there a way to eliminate the possibility the head gasket has been compromised? (is there a test that will verify combustion gasses are not in the coolant?)

 

Thanks,

 

Tracy

 

I would say its one of three things, A- an air pocket, or B- a cloged radiator C- missing radiator fins. Radiator flushes over the counter dont really work all that well on a hige milage radiator. Also one other thing to consider. I had the same problem and decided it was time to replace the radiator. I ordered one of the net (www.radiator.com great people, they know cars). I pulled it out, and 30% of the cooling fins were gone. I could not see it because the AC was in front of the radiator. From the fan side the radiator looked fine.

 

 

nipper

[nipper]

Water pump stator erodes over time. usually the bearing fails long before that happens.

Head gasket is an easy one. Start the car with the radiator full and the cap off. Let the car warm up so the thermostate opens. If there are bubbles, then you have a blown head gasket. Tiny bubble will go away, these are from the onrush of radiator flow. Big bubbles from a blown headgasket will not go away.

 

nipper

[tcspeer]

The radiator may just need to be taken out and and have the fins washed out, with water hose. Be careful and not spray with to much force that it would bend the fins. This happened to my car at around the mileage yours has and that fixed it.

[fj401968]

The radiator doesn't look all that bad but who knows what's stuck between it and the A/C radiator. I did run a garden hose with a squirt nozzle carefully across all the rows the day I flushed the radiator.

 

It could still be compromised though either from the inside or outside which causes it to run hot under load... but what about the random temperature spikes? Can the coolant system *really* get persistent air bubbles like has been mentioned?

 

Tonight I'll run it with the radiator cap off and look for head gasket leak bubbles... I've done this before and couldn't really tell one way or the other. Also, I've read that a subtle head gasket leak can be the cause of the overheating demons and yet not produce visually noticeable bubbles from looking into the radiator.

 

I called a subaru shop in Idaho Falls a few weeks ago... admittedly I 'primed' him about the possibility of a head gasket issue and he said it was the likely culprit.

 

Of course I don't want this to be the problem because A.) I'm not going to put $1200 into the car. It isn't worth it at this point (that's what the mechanic quoted for *him* to do it). B.) I don't feel like doing that extensive of repair work myself on this car. I only have so much time and I have an '87 GL wagon that needs a clutch and is more worthy of the 'wrench time'. However, like I said, I'd love to get some more mileage out of this car so if it is something stupid-easy like a bad radiator, I'll suck it up and change it. If it's the head gasket, I think I'll just drive the car until it blows up and then junk it. It has been a bit of a lemon and is getting kind of beat up to boot.

 

I really appreciate the input folks!

 

Tracy

 

The radiator may just need to be taken out and and have the fins washed out, with water hose. Be careful and not spray with to much force that it would bend the fins. This happened to my car at around the mileage yours has and that fixed it.

[nipper]

Well the next easiest way is find a station with an exhaust gas analyzer. Let them sniff the radiator and see if they smell any exhaust gasses.

 

 

nipper

[1 Lucky Texan]

I vote bad catalytic converter.

[Setright]

My EJ22 did exactly as you describe when it blew a head gasket. Don't waste too mcu money on replacing radiators and thermostats and water pumps. FIx the HG.

 

Or, if you don't intend to spend that much on the car and are willing to run it into the ground: Fit a higher pressure radiator cap.

 

1990 Legacy will probably be 0.9 bar. Get one for a newer model at a dealer, and it'll be 1.1 bar. It'll slow the bubble process while you look for a new car :-)

[drewd]

I parked the bronco on a steep driveway, removed the radiator cap and let her run until the temp gauge was in the middle...that's where it normally is when i'm running the truck after a while. When the thermostat opens keep feeding it distilled water until it over flows a little...look for the bubbles...if nothing, turn the car off and put the radiator cap back on.

 

Some mechanics can tell if the HG has been leaking by looking at the exhaust manifold...when my Ranger blew a HG the mechanic told me he saw white streaks against the rusty manifold and that it was leaking for a long time. Maybe some people on the board can tell you where and what to look for.

[fj401968]

Yeah... I really do think this is probably the issue. The radiator looks pretty darned good and the problem surfaced suddenly and not gradually.

 

It appears to be getting worse recently too. It seems like a plugged radiator would present itself as a very gradually increasing, chronic problem.

 

Even though the AWD doesn't work anymore and the auto-trans is a bit clunky and the car is getting a bit beat up, it is still a comfortable car with fairly new struts all the way around (the air stuts died and I replaced them with standard struts) and good rubber. It has a working moon roof which I enjoy and drives well.

 

I'm reasonably handy with a wrench... should I just suck it up and pull the heads, have them flattened and put on new head gaskets on both sides? OR... should I say with a smile, I've gotten nearly 100,000 miles out of the car since I bought it, that's not too shabby and just drive it into the ground? Dilemna!!

 

History: bought car for $2500 (99,000) rebuilt trans at about 110,000. Cost: $1500. New struts $400-ish. Other maintenance along the way: Half shafts, brake pads and rotors, tires, alternator, tune-up, etc... The car has about 192,000 miles on it at present. Haven't done anything major to it for the past 60,000 miles.

 

Thanks,

 

Tracy

 

 

My EJ22 did exactly as you describe when it blew a head gasket. Don't waste too mcu money on replacing radiators and thermostats and water pumps. FIx the HG.

 

Or, if you don't intend to spend that much on the car and are willing to run it into the ground: Fit a higher pressure radiator cap.

 

1990 Legacy will probably be 0.9 bar. Get one for a newer model at a dealer, and it'll be 1.1 bar. It'll slow the bubble process while you look for a new car :-)