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overheating only when driving


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10 replies to this topic

#1 crazyeric

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Posted 16 August 2003 - 01:28 PM

i have a 1990 subaru legacy and if I start it up and just let it run it will be fine, but when I start driving it, after about a half mile the temp guage will start to go up and if i pull over and pop the hood, the rad. hose is rock-hard from pressure which led me to believe a problem with the thermostat. I put a new thermostat in and im having the same problem, i tried burping the radiator with the vent plug on the passanger side and just ended up getting hot coolant sprayed all over me. Has anyone had this problem or maybe know whats going wrong, it just seems like when i start driving none of the coolant is getting through the engine. Thanks alot, Eric.:banghead:

#2 frag

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Posted 16 August 2003 - 01:42 PM

Like I said on the old thread, your symptoms seem to point to cylinder pressure getting into the water jacket (head gasket leak, cracks...).
Look for air bubbles in the overflow thank or oil in the coolant.
Those that had this happen to them will certainly chime in.
In the meawhile, answering Subiegal would be helpful to those trying to help you: what do you mean by "my radiator blew up"? What symptoms? How did it happen?

#3 crazyeric

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Posted 16 August 2003 - 03:48 PM

i tried to reply on the old board but it wouldnt let me, anyway.. i drove it like 5 miles and when i got to where i was going smoke was pouring out of the hood and when i popped it there was lots of steam coming out of a 4 inch crack in the plastic side of the radiator. I was thinking of running it without a thermostat to see if that would work but i dont have time right now to try it out, well thanks again, Eric.

#4 theotherskip

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Posted 16 August 2003 - 04:20 PM

the system will normally be under pressure (around 12psi). if you open the system while it is pressurized, it will spray coolant. the safest way to open the system is to wait for it to cool (at least 3 hours), then open the radiator cap slowly.

after verifying that your radiator is full and burped properly, you should make a pencil mark on your expansion tank, then drive the car for a 20 mile run to get the system fully heated up and up to pressure. then check the expansion tank. the level should have risen. if you see bubbles coming from the tube connected to the radiator, either you haven't completely burped the system, or you've got problems (head gasket, etc).

#5 edrach

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Posted 16 August 2003 - 08:11 PM

Sounds like you have a couple of problems. The radiator cap should release at 13psi. If it doesn't you can build up enough pressure to blow a hose or radiator. Sounds like you already breached the radiator. Firstly, get a new radiator cap. Then investigate why this is happening. Starting with a cool engine, remove the radiator cap and start the car and fill with a 50/50 solution of water (distilled is best) and coolent. Keep topping off the coolent until you don't need to add any more. If you have a blown head gasket, coolent will gush out of the raditor and you won't be able to fill it properly. When the coolent is topped up (and assuming it's not gushing out), replace the radiator cap and test drive it. It's normal for the coolent to come out of the radiator through the cap and go into the overflow reservoir. After you shut the engine off and it cools, coolent is drawn back into the system. Judging from your other comments, I suspect you'll need to replace the radiator too.

#6 gotsubarus

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Posted 17 August 2003 - 09:29 AM

Hey, First of all your radiator is cracked on the front of the tank on the right side ( Passenger ) throw the radiator away and get a new one. Thats is the side that the hotest water returns to the radiator. If you get a used one you might get lucky and get a good one ( but remember your using a 10 to 13 year old radiator that you know nothing about how well it was taken care of )

When filling radaitor...Fill it till full with the radiator bleader screw out.. also fill it through the bleder screw side also. Fill it till fluid pours from both sides.

Did you get a new thermostat from Subaru? Some aftermarkets do not work very well.... Test your system by removing the old thermostat and cutting the center out of it and place back in ( you might have to replace the rubber O ring if it leaks when filling it... you can run it a few days or longer like that it wont hurt. If it runs cool replace with a new thermostat from SUBARU and replace the cracked radiator with a good aftermarket ( I use Modine )

Check your fans to see if they are working.. It is easy to check the AC fan .... just turn on your AC and the fans should start running

#7 crazyeric

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Posted 26 August 2003 - 10:00 PM

removed the thermostat today and left the rubber gasket as a seal. Temp guage doesnt get any more than a little under halfway. The check engine light came on but went off after a few minutes. There were a few bubbles in the reservior but they went away when i loosened the vent screw. Also coolant bubbles out of the vent screw when i loosen it. How long would it be safe to go without a thermostat for?

#8 theotherskip

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Posted 26 August 2003 - 11:20 PM

you can go forever without the thermostat. it will take longer to get up to temperature, and won't always stay warm, especially if it is very cold out. it only cost about $15 to replace it, so that is probably your best option...

#9 nickb21

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Posted 26 August 2003 - 11:30 PM

Not positive about a '90, but if the motor never reaches operating temp, the computer will stay in closed loop mode, which keeps the mixture rich..

#10 crazyeric

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Posted 01 September 2003 - 12:21 AM

i tried with both thermostats, the stock one that was in there and the cheap one from napa, both overheated, been driving it with no therm for 5 days or so and it doesnt give many problems except for a check engine light every now and then, ill just run it till i really need heat.

#11 subieman

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Posted 01 September 2003 - 12:52 AM

I don't know what it is about gen 1 Legacys, but after time they start to overheat. My 91 with 207k on the clock overheats like mad when I have the thermostat installed. To this day I have not figured out what the problem is. Replace the radiator, hoses and thermostat. But when the stat is in, the temp gauge rises to the top. I gave up, and I run without a stat now. Been that way for about a year. During the winter months I stick a piece of cardboard in front of the radiator to keep the motor warm. Maybe it's a blown head gasket, but it shows no signs other then overheating.

Good Luck




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