Every head gasket repair comes with a written warranty.
There are various techniques that can be used to determine a blown head gasket. Be very careful when performing these tests, when a vehicle has a blown head gasket, the engine can overheat quickly. The cooling system can also build excessive pressure which could cause the cooling system to rupture. Even a very small breach in the head gasket (often the diameter of a paper clip) will allow exhaust gases to enter into the coolant system. If exhaust gases are present, a head gasket repair will be required. A very common method to test for exhaust gases is a block test kit, which can be purchased for around $50 or most auto parts stores will provide the kit on a “loaner” basis. You will usually have to purchase the test fluid, the price is around $10.
If a blown head gasket is suspected, performing a simple block test will often show exhaust gases in the cooling system. Sometimes a head gasket can be blown, but show no exhaust gases in the cooling system. If the head gasket has failed between two cylinders, a breach in the head gasket will let the compression of one cylinder leak into the second cylinder. This can be verified by performing a compression test. If there is a leak in the head gasket, typically white smoke will come out of the exhaust pipe & overall power will be lost.