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Should you wait until your car overheats to fix a blown head gasket?

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Dear Tom and Ray:



I have a 2002 Subaru Forrester. Upon my monthly check of fluids, I was shocked to see that there was no cooling fluid in the reservoir. I immediately took it to the shop, where they told me the head gasket was blown, and it would cost 2,000 dollars to fix. After doing some research, I found that Subaru had a service bulletin about this problem and advocated the use of a special Subaru additive for the coolant that could "possibly" stop the leak. So, I asked the mechanics to put the additive in my coolant. My mechanics then advised that I should just drive the car until it overheats, and only then fix my head gasket. So I have two questions: (1) Is it truly possible that this "additive" will fix my leak? And (2) if the additive doesn't fix my leak, should I really wait until my car overheats to fix it? Thanks. -- Catherine

TOM: It IS possible that the additive will fix your leak. For years, Subaru has had problems with its head gaskets "seeping." They would remain intact (i.e., not torn or broken), but would allow fluid to seep through or around them. And if your head gasket is just seeping, and not actually blown, the additive may work.

RAY: I've tried the additive on my scalp, but somehow bald spots are still seeping into the regions where I once had hair.

TOM: The fact that you check your levels every month is actually discouraging to us, Catherine. Because that means the coolant reservoir went from full to empty in less than a month. That suggests that the solution may involve your home equity line in addition to the additive. But by all means, try the additive first.

RAY: But don't just wait for the engine to overheat. That's bad advice.

TOM: Right. Let's say your head gasket really is broken. You try the additive, it doesn't work and the car overheats. If it overheats badly enough, you could crack or warp the heads or damage the block. Or you could degrade the oil so badly that you damage the engine's bearings, which will shorten the life of the engine considerably. So you really don't want the car to overheat, ever.

RAY: Instead, now that the additive is in there, check your coolant reservoir every day for a while. See if you can assess whether the level is continuing to drop, and if so, how quickly. If it stops losing coolant, then have your garage do a pressure test and, hopefully, proclaim the problem solved.

TOM: But if the coolant level continues to drop, you want to find someone to fix it before the car overheats. And I'd suggest that that person be a different mechanic.

RAY: Right. Your current guys didn't know about the Subaru additive, and they gave you bad advice about what to do next. Ask friends who own Subarus who they use in your area. Or check out The Mechanics Files at www.cartalk.com. And let us know how it works out, Catherine.
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