my subaru radiator overheats after coming off of a long fast highway drive. Why?

Hi Span, Either you have a faulty guage (not likely) or your thermostat has gone bad. You can pick a new one up for under $10. It's usually located on the block side of one of the radiator hoses. There will be a housing with a couple of bolts. Hope this helps!

The best info i can give is..... Join the SVX world network at: www.subaru-svx.net The ppl there are very helpful and most questions have been asked, and we have our own "line" of upgrades. I am currently making sway bars for the group (well whomever buys them)

My ’98 Subaru Outback, with the 2.5L, had a similar problem, sometimes on back roads it would overheat too. The thermostat was replaced and it kept overheating. My mechanic pressure tested the car to test for a bad head gasket 2 times, but each time the test results showed that the head gasket was fine. Eventually the head gasket was replaced and never overheated again. From my understanding this was a very common problem with the 2.5’s.

I'd recommend checking out a bunch of different forums, that is definitely the best one, but there is more info out there on the others too. Just Google Subau SVX forums...

There is the definite possibility that your head gaskets are bad. Not a function of miles, but of age. These are becomming more and more common as these cars get older. Car may have normal operating temps and then the gauge moves uo into the red. May come back to normal by itself and rise again unexpectedly. I replaced mine in my 1996 Polo after similar symptoms. Car had only 125,000 miles. Has been running perfectly ever since. The bad news is this is about a 1300.00 job. Since the engine had to be disassembled and the heads milled, now is the time to replace timng belt water pump, spark plugs, and gaskets and seals

you need a new water pump, the impellor in your water pump has broken as a result when you drive your vehicle slowly the water is cooled sufficiently but when you use a faster road it can cool qhick enough due to the impellor unable to drive the warer around at a fast enough speed, quite,advise changing timing belt at same time, fatherbear

think your thermostat needs to be replaced, but while doing that, consider replacing your gaskets as well...