YACT: Engine overheats when at city speeds, but not highway speeds

[sciencewhiz]

First of all, my car is an 82 Subaru DL with 189k miles on it. I've already put $500 into it so far this year (more then the KBB value). All I want is for the car to last till the end of November, without putting any more money into it.

My commute to work is about 4 miles through LA. By the time I get there, the engine temperature is solidly in the red. If I let it idle for a minute or two, the temperature goes down to just above the half way mark. I don't actually overheat, because the times that I'm at stop lights lets the engine cool.

If I go on the freeway, at 70 or so, my temperature stays at just above the half way mark.

If I'm in constant slow traffic, like constant 10 or 20 (freeway at rush hour) the engine overheats.


Anyone have any idea what could cause this? I would have though at highway speeds, then engine would have to work harder to maintain the speed and thus overheat.

 

[notfred]

On the freeway you have a 65mph wind blowing cool air over your engine.

Is the fan spinning when the engine is running?

 

[Ryan]

But, at high speeds, more air is rushing through the radiator, thus cool the coolant more quickely.

 

[Kelvrick]

Are you also in a lot of stop and go? Does the temperature go down when you speed up?

I'm thinking your radiator fan is broken. I hate how those things cost so much.

Could also be your thermometer.

 

[Mr.IncrediblyBored]

Maybe check the radiator fans to see if they are working.

 

[Vic]

Check the radiator fan, sounds like it isn't working.

doh! beat by a minute ^^

 

[CraigRT]

COULD be an old rad... but likely fan or thermostat i'd guess.

is it getting worse? if so, you may be losing coolant...

 

[Mr.IncrediblyBored]

Also, some electrical systems will not turn on the radiator fans unless the engine temperature is over a certain threshold. If the thermostat for this is broken, the fan may never turn on. Not sure if this applies to your car, but I believe my motorcycle radiator operates like this.

 

[sciencewhiz]

The last time I took it into the shop, they replaced the radiator cap and claimed they fixed it, but it only got a little better.

I guess I'd need to drive it a bit, then see if the radiator fan is still running? How would I go about determining if it was the fan or the thermostat?

My commute is city traffic, the fastest I go between stop lights is 40 or so, and it doesn't cool down at that speed.

Edit: Also, is it ok to drive my car like this for the next month and a half, or am I going to completely destroy it?

 

[Mr.IncrediblyBored]

If the fan is running at normal speed after driving around for a while, then the fan is fine. I would check your coolant level and look for puddles of green liquid underneath your car. If the coolant levels are OK, then the radiator (or some other hose/pipe) could be clogged or the water pump may be broken.

edit: I'm not sure what would be the best way to test the thermostat. Maybe put the thermostat in some water and put the water on the stove and start heating it up. It should "open" before the water starts to boil.

 

[sciencewhiz]

Coolant level is fine.

 

[Analog]

thermostat is not opening fully, or bad fan/fan circuit.

 

[Thegonagle]

Electric fan?

My '88 Subaru's fan was belt driven.

For a car you're going to junk in December, I suggest the following:

If it's belt-driven, the fan clutch may not be working anymore. Find a way to "seize" the fan clutch, like by running nut and bolt through it at a strategic location.

If it's electric, test the motor by jumping it directly to the battery. If it comes on, connect the fan motor to a low beam wire (it should handle the current) and drive with your headlights on.

If the electric fan does not come on, well, it's not going to be too hard to fix, but locating a cheap used part may be a hassle, so in that case, roll down your windows and run the heat at full blast when the engine starts to get too warm.

(EDIT: Or you can decide to do nothing, and just roll down the windows and run the heat full blast when the engine temp starts to climb.)

 

[VirginiaDonkey]

It is your radiator.

All early/mid 80's Subarus have the problem of the fins separating from the tubes in the radiators, thus reducing the contact area for the air to cool the engine.

There are dual core radiators you can buy to fix that problem if you want to keep your car. Here is a great site for Subaru help. Lots of good people and cheap parts too.

Subaru site

I know this problem...I had a 86 GL and it had the same issue....especially in the summer

 

[RedRooster]

How's your tire pressure?

 

[Lithium381]

my 82 honda did that too.......the thermostat was broken, so it didn't know it was hot, so it never turned on my fan......:-\

 

[Evadman]

Originally posted by: RedRooster
How's your tire pressure?

Dude! his tires were only at 23 lb's instead of 25! OMG! That was it! He put 2 one pound cans of air into the tires, and the problem vanished!

 

[NutBucket]

Man, that really is a POS. My friend's family has an '82 Sub. wagon has had soooo many problems and it only has about 90k on it. Other then driving around with the heater on, I would say you follow the other suggestions and just wire the fan to be on all the time (pretty sure it has an electric fan, but I don't remember for sure).

 

[sciencewhiz]

The fan is most definetly on (checked it tonight)

My tires are slightly overinflated (although I can barely read the sticker on the door).

 

[toant103]

Originally posted by: sciencewhiz
First of all, my car is an 82 Subaru DL with 189k miles on it. I've already put $500 into it so far this year (more then the KBB value). All I want is for the car to last till the end of November, without putting any more money into it.

My commute to work is about 4 miles through LA. By the time I get there, the engine temperature is solidly in the red. If I let it idle for a minute or two, the temperature goes down to just above the half way mark. I don't actually overheat, because the times that I'm at stop lights lets the engine cool.

If I go on the freeway, at 70 or so, my temperature stays at just above the half way mark.

If I'm in constant slow traffic, like constant 10 or 20 (freeway at rush hour) the engine overheats.


Anyone have any idea what could cause this? I would have though at highway speeds, then engine would have to work harder to maintain the speed and thus overheat.

water pump?