I have a 97 subaru outback. has about 180k miles on it and i was driving on a 3 hour trip.

10 minutes before the end of my trip, I filled up gas and when I restarted my car, the temp gauge was all the way up.

I started driving again and the temp went back to normal.

when I arrived at my destination (10 minutes later), the temp was going up again.

I shut off the car and then white smoke came out of my hood.

seems like a cooling problem to me.

so i took it to a shop and they idled the car for a bit. about a minute into idling, the car started reving by it self from about 1k to 1.4k and back down to 1 on and off.

what would this idling be?

first thing we noticed is one of the cooling pipes that should be hot, wasn't. so the mechanic said the cooling wasn't circulating.

so my initial thoughts are either thermostat or maybe water pump?

mechanic thinks it might need a head gasket?

defitneily overheating problem?

any thoughts? especially the wierd idle?

I have a 97 subaru outback. has about 180k miles on it and i was driving on a 3 hour trip.

10 minutes before the end of my trip, I filled up gas and when I restarted my car, the temp gauge was all the way up.

I started driving again and the temp went back to normal.

when I arrived at my destination (10 minutes later), the temp was going up again.

I shut off the car and then white smoke came out of my hood.

seems like a cooling problem to me.

so i took it to a shop and they idled the car for a bit. about a minute into idling, the car started reving by it self from about 1k to 1.4k and back down to 1 on and off.

what would this idling be?

first thing we noticed is one of the cooling pipes that should be hot, wasn't. so the mechanic said the cooling wasn't circulating.

so my initial thoughts are either thermostat or maybe water pump?

mechanic thinks it might need a head gasket?

defitneily overheating problem?

any thoughts? especially the wierd idle?

Take my advice/comments for what they are worth....I am not an expert.

Do you have carbon flakes in the coolant?
Is the reservoir bubbling?



I would start by replacing the thermostat....it is cheap and easy to replace. This is one you can do yourself in the driveway.

Also would look at replacing the radiator cap.

But chances are you have a headgasket leak. Best way to determine this is to do a leakdown test. This test basically determines if the piston chambers are holding compression. They are supposed to be airtight. But if there is a leak in the headgasket or in the valve seals...then you will lose compression.

This is a test you can do yourself. You can buy the gauge w/ hose attachment at any local parts store. You basically remove your spark plugs and screw the attachment at one end of the hose into the spark plug hole. You then crank the engine and take readings off of the gauge. Two basic things you look at...(1) How far does the needle on the gauge move up (how much compressions builds up) and (2) Does the needle start to fall (is the chamber losing compression du to a leak)

You can do a google on leakdown test or compression test....or you can search this sight as well; for better directions.

You will also need to do research specific to the Subaru engine...because they have their own peculiarities. Sometimes these engines seem to pass the test, but still have a leak.

Here is a blog write-up that has pretty good info.

http://home.comcast.net/~skipnospam/Head_gasket_replacement.html

But chances are you have a headgasket leak. Best way to determine this is to do a leakdown test. This test basically determines if the piston chambers are holding compression. They are supposed to be airtight. But if there is a leak in the headgasket or in the valve seals...then you will lose compression.

This is a test you can do yourself. You can buy the gauge w/ hose attachment at any local parts store. You basically remove your spark plugs and screw the attachment at one end of the hose into the spark plug hole. You then crank the engine and take readings off of the gauge. Two basic things you look at...(1) How far does the needle on the gauge move up (how much compressions builds up) and (2) Does the needle start to fall (is the chamber losing compression du to a leak)

Just an FYI, what you just described is a compression test. Before anything is done, the ignition and fuel systems must be disabled. The ignition system can be disabled by unplugging the 3 wire harness to the igntion coil on the top of the intake manifold. The fuel system can be disabled via removal of the fuse or relay going to the fuel pump. I haven't peformed a compression test on my Subaru, so I can't say which fuse/relay box it will be located, but I would think it would be in the box under the hood.

The throttle should be open to allow airflow into the combustion chamber. I would suggest having a second person sit in the car with their foot on the throttle pedal, but you could probably rig something up.


When you do the test, note that all the cylinders should be at least 100psi, and should not vary from eacy other more than +/- 10%. If the car fails this test, squirt about 1tbs of oil into the cylinder, crank the motor a few times to distribute it, and retest. If the car now passes this test, you could have much bigger problems than a simple head gasket leak.

If the car failed both tests, you should then go onto a cylinder leakage test. Unless you have the tool (or made one yourself) as well as an air compressor, I would suggest taking the car to a local garage and have them perform the test. This involves pressurizing the cylinder, typically to 160-175psi, and the cylinder you are testing (the one that varied more than 10% from the rest) should be at TDC on the compression stroke. The tool is fitted into the spark plug hole, and the cylinder is pressurized. You would then check for hissing/etc.

If the engine hisses out of the exhaust, the problem could be a burnt exhaust valve.
Intake - burned/non seating intake valve
Between the head and block - head gasket
Coolant bubbles - head gasket, cracked cylinder head, water jacket leak
Dipstick - blowby (rings/pistons)
Adjacent spark plug hole - head gasket

Some of those situations wouldn't contribute to your overheating problem, but I included them for completeness.

Have fun. I would start with what Mike said, the thermostat and radiator cap as they are your cheapest options. Even so, the idling problem suggests something more serious, such as a head gasket.