Block Test
PERFORMING A BLOCK TEST
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.
Steps to perform a block test:
- Remove the pressure cap from the radiator or expansion tank, check to see that the coolant level is low enough to prevent any coolant from getting into the test equipment (approx. 3″ below the fill hole). It may be necessary to drain enough coolant out to prevent the contamination of the test fluid.
- Warm the engine, and allow it to idle during the test. Coolant must be circulating so the exhaust gases can enter the cooling system while this test is in process.
- The color of the test fluid before pouring it into your test equipment should be blue. If the fluid is green or yellow, the fluid is too old and should be replaced with blue test fluid.
- Pour test fluid into a glass tube to the fill line.
- Insert the cone of the test instrument onto the neck of the radiator or expansion tank, ensure there is a tight seal.
- Insert the squeeze bulb into the top of the test instrument and squeeze it for about a minute to pull radiator gases through test fluid. If exhaust gases are present, the test fluid will “sniff” the gases as they are pulled through the fluid. If the blue fluid turns yellow or green, exhaust gases are leaking into the coolant system, and a head gasket repair is required.
- If fluid remains blue, exhaust gases are not present in the cooling system.
- If a blown head gasket is suspected, but the block test passes, it is possible that the head gasket breach is between the cylinders. Sometimes a vehicle can still have a blown head gasket without exhaust gases leaking into the coolant system. A compression test will be required. Call Ideal Head Gasket Repair for help in diagnosing a blown head gasket.
Compression Test
PERFORMING A COMPRESSION TEST
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.
Steps to perform a compression test for a blown head gasket:
- Remove the engine’s spark plugs.
- Insert a compression gauge to a spark plug opening.
- Crank the engine to observe the maximum gauge reading, write down that reading.
- Repeat the procedure for the rest of the remaining cylinders.
- Compare the results of each cylinder. If the reading on two or more adjoining cylinders is much lower than the rest of the cylinders, the head gasket is damaged.