Subaru Forester thirsty for radiator fluid

2001 Subaru Forester that glugs about 1 liter of antifreeze/75 miles. Has stumped my mechanic and the dealership – who offered to charge $2000 to explore their hypothesis that the leak is at the cylinder head gasket, but couldn’t guarantee the problem would be fixed. (My mechanic thinks that hypothesis doesn’t fit because the car doesn’t smoke/burn coolant.) Radiator doesn’t leak. Thermostat has been replaced (which solved initial problem of overheating). I think my mechanic has given up, and I don’t want to spend $2000 to POSSIBLY fix the problem! HELP!?!

Well it sounds like a head gasket to me. I would at least get a compression test. I would not rule it out even without seeing smoke etc.

It it is using a liter in 75 miles it is going somewhere. The cooling system can be tested with a pressure test and see what happens.

Also, a leak-down test will check the integrity of the combustion chambers. Both test can be done for far less than 2 Grand. Ask your mechanic about that, instead of the money-hungry dealer.

I agree with Joseph on the two tests. (The 2nd test is a coolant pressure test)

No smoke from the tailpipe, so the intake manifold gasket may be the culprit.

Wait a sec. The T-stat was replaced which solved the initial problem of overheating. Does it overheat now?

1L of coolant per 75 miles is a lot.

You’re certain the coolant reservoir hasn’t got a pinhole or tiny crack in the joint?

Is the coolant pressure test the same thing as putting the radiator under pressure to test for a leak? I know that was done and no leak was found.

The car has not been overheating since the thermostat was replaced (once we realized that we had to serve it coolant every 1-2 days).

Initially the reservoir wasn’t losing coolant at all; we would have to refill the radiator directly. My mechanic replaced the radiator cap b/c he said the rubber on the old one had worn off, and since then the reservoir is feeding the radiator again. The “check engine” light also went off after the radiator cap was replaced, if that’s worth anything.

Thank you all for your input. I will ask my mechanic about a compression test, pressure test, and leak-down test.

Yep. The rad can be isolated for a separate test if needed, but the coolant pressure test is usually done to ascertain if the head or intake manifold gaskets are leaking.

Whenever coolant is lost slowly but steadily and there is NO visible external leak, thoughts turn to the possible internal leaks.

These can turn into very expensive repair costs if not soon addressed.

$2000 to check the head gaskets? I would find a different dealer first. Also, a 2001 Forester should be covered under Subaru’s extended warranty for the head gaskets…something like 8 years/100,000 miles. There were all sorts of internal/external leakage issues up until 2002 (and some say post-2002 as well).

I actually found that warranty information recently, but when I raised the question with the dealership, they said it only covers external leak. Since mine is internal it wouldn’t be covered. But then they offered (through some agreement with their Subaru rep? – wasn’t clear) to halve the cost and charge me $1000. I’m thinking about that one now.