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Dear Rob:

I was told at the repair shop that my truck's 4.6 litre V-8 engine has a blown head gasket and that it will cost well over $2,000 to fix it, as the cab has to be removed in order to get the heads off.

I saw an ad recently that claims a product known as Bar's Leak will seal blown head gaskets. I suppose the size of the leak is a major consideration with respect to the efficacy of the product, but are you familiar with this product and is it worth trying?

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Thanks, Barry

Although it's true that Bar's Leak is a product designed to seal cooling system leaks, asking it to control coolant leaking across a combustion chamber is like trying use your hand to stop the fizzing from a two-litre bottle of soda. In other words, Bar's Leak wasn't created to seal combustion pressures – no matter how small the rupture in the head gasket.

The bad news is that you will have to have the offending gasket replaced and yes, Ford tucked the engine so far back in the chassis of their F-series trucks that the cab must be lifted off to gain access to the cylinder heads. But the good news is that most Ford dealer shops have this process down to an art so don't be afraid of this job. As a matter of fact, removing the cab provides so much access that the quality of the repair is often better than a similar repair on a vehicle that does not have the ability to remove the body.

Speaking from experience, reaching over the fenders and radiator support to remove and replace V8 cylinder heads is an extremely awkward and frustrating job. Not having full and clear access to the block surfaces to clean the old baked on head gasket doesn't guarantee a perfect repair.

Sometimes mechanics wish they were born with eyes at the ends of their fingers because with this type of job, the only way to "see" the work is to feel along with fingers.

Sorry it's not the answer you were looking for Barry.

Send your automotive maintenance and repair questions to Globe Drive experts at globedrive@globeandmail.com

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