A blown head gasket will cause the car to overheat easily, and coolant viscosity may increase. This may also indicate a leak in the cooling system, but a simple pressure test should be able to tell you if that is the case. The white smoke may be coolant burning. I’m not sure of any definitive tests for it, but it will be even more expensive if you try to drive with a blown head gasket so it is best if you get an opinion from a trained mechanic before you do anything.

Sometimes the coolant in the exhaust will condense on the way through the exhaust system, and your tailpipe may drip, but that is far from definitive, since by that time other damage has already been done. If it were my car I would take it in for service.

Get a compression check. This involves removing a spark plug and inserting a gauge in the socket. It’s a fairly quick test that any shop can perform. If you are mechanically inclined, you can pick up a compression gauge and do the test yourself.

The bad news is that it could be worse than a head gasket. You could have a crack in the cylinder block.

If the smoke is a bluish white, it’s probably your head gasket.
Bummer.

When my Subaru did this, (due to the bastards at Jiffy Lube) I got a $800 replaced engine from Japan, and just put a new one in.

if your oil on the dipstick looks like chocolate milk after letting the motor run for a couple of minutes, the head gasket is bad or the head is warped or cracked.. The other symptoms you described can be attributed to a blown head gasket or a cracked or warped head. If the car was overheated and the head is aluminum, the the head could be warped. Expensive fix either way. Good luck.

Thanks to everyone for their responses so far! I’ve managed to get my local mechanic friend to come round tonight, and he has mentioned doing some pressure test on the cooling system as well as a compression test.

My phone call to Subaru for a cost for a replacement gasket = ”...about a thousand quid all-in.” Gulp! :(

There will be 2 headgaskets in your case i’m afraid. If you really like the car (who wouldn’t) You will already past halfway there to go ahead with a rebuild and a more.. uh.. performance cam. Add that bit of off-the-line ‘grunt’. Done it, glad I did. essentially a brand new engine!