Anyone try this Bar's Leaks Radiator Stop Leak on their car?

I know the thermostat has been replaced at the beginning of all this, but I'd change it again just to eliminate it. It may not be opening fully, which would cause overheating at speed. Other things can cause it, yes, but this would be a cheap and easy test. New parts can be defective, too.

But that wouldn't explain the volume of coolant he's losing.

If the coolant is boiling in the block, that would force coolant out the cap. But you're right, if it's not coming out the cap, it's going elsewhere - and the exhaust is white. My bad.

Yes, Subaru's did have this problem! The mechanic in the shop has alot of experience and has changed Subaru head gaskets in the past. He claims Bar's Leaks was recommended by Subaru and I really think I could not have driven the 90 mile drive home without it!

Ok, BeGreen

Here is what happened. We took the car back and had the head gasket replaced again under the warranty!
No cracks in the block or heads and the heads were resurfaced again. The thermostat was locked up closed which means when I just barely got the car home with no damage! It does seem that the T-stat freezing up was a RESULT of the overheating and not the cause, since it was working and it was new when they did the 1st head gasket replacement. So I am still a little puzzled as to what happened?

Any comments?

trade it, quick.

I hate to say Smoke, but you maybe right on!

A really good overheat or two (or five.... ) can easily cook a thermostat. Would probably vaporize the wax pellet beyond ever functioning again. Would've asked them to MagnaFlux the head(s) for cracks at this point too. Were they able to rule out the other head being a problem or confirm that the head that was repaired was indeed the one leaking again?

The mechanic shop sends the heads (Yes they did both - the Felpro gasket kit is a set of 2) to a machine shop. The machine shop checks them and if they are good, resurfaces the heads and sends them back. They sent them back and did not say they were bad. Do you think $120.00 would include the MagnaFlux of the heads?

Did you see the attached receipt? I copied the machine shop portion below.

Receipt show's Machine shop work
MACHINE SHOP SERVICE TO CHECK OVER 120.00
HEAD AND RESURFACE

It doesn't say heads, it says head. And 120 bucks sounds about right to magnaflux and mill 1 head. 2 heads and that would be a very good price indeed. They may be using the gasket kit with 2 gaskets in it but only doing one side or the other. The kit is still a good way to go as it would contain all the auxillary gaskets one would need even if you don't use both head gaskets.. It would be unusual for them to pull both heads unless there was a pretty obvious cause to do so.