SMOKE COMING FROM TAILPIPE (Blue, Black, White)
by Lance Wright

SYMPTOM SUMMARY
The vehicle emits excessive smoke from the tailpipe.

USUAL CAUSE
Smoke from the tailpipe can be caused by several things depending on the type of smoke emitted.

DIAGNOSIS
The color of the smoke is an indicator as to what the failure is. Blue smoke is generally caused by excessive oil consumption that is being burned in the combustion process. White smoke can be normal on cold engines during cold ambient temperatures, but should diminish once the engine is warm. If white smoke is present after the engine is fully warmed up, the usual cause is water ingestion into the combustion chamber. This can be caused by a blown head gasket or cracked cylinder head. Black smoke is a key indicator that too much fuel is being consumed by the engine. This can be caused by anything from a computer malfunction to a leaking fuel injector. If the vehicle is emitting white smoke you should inspect the coolant level. If the coolant level is low or the vehicle also exhibits an overheating condition, the most likely cause is a blown head gasket or cracked cylinder head. In either case, the cylinder head(s) will have to be removed and inspected. Once removed, the cylinder head should be pressure tested and checked for cracks using special equipment by an automotive machine shop. Additional tests can be done on the vehicle prior to disassembly to confirm the diagnosis. A “Block Test” can be performed that will detect the presence of combustion gases in the coolant. This test consists of pulling some of the vapors from the radiator into a glass tube filled with a special chemical. A change in the chemicals color will confirm exhaust gases in the cooling system. Block Testers are available at most auto parts stores.

PRECAUTIONS, TIPS, and NOTES
The cooling system is under pressure when the engine is hot. Removing the radiator cap while the engine is hot can cause severe burns. Check the coolant when the engine is at ambient temperature. A complete functional test of the cooling system should be performed after any major engine repair. Often, a blown head gasket is the result of an overheating problem caused by another failure such as a defective thermostat, restricted radiator, or coolant leak. You should ensure the root cause of the blown head gasket diagnosed to prevent duplicating the problem. It is recommended that the thermostat be replaced during any major engine repair. If the vehicle is emitting white smoke you should inspect the coolant level. If the coolant level is low or the vehicle also exhibits an overheating condition, the most likely cause is a blown head gasket or cracked cylinder head. In either case, the cylinder head(s) will have to be removed and inspected. Once removed, the cylinder head should be pressure tested and checked for cracks using special equipment by an automotive machine shop. Additional tests can be done on the vehicle prior to disassembly to confirm the diagnosis. A “Block Test” can be performed that will detect the presence of combustion gases in the coolant. This test consist of pulling some of the vapors from the radiator into a glass tube filled with a special chemical. A change in the chemicals color will confirm exhaust gases in the cooling system. Block Testers are available at most auto parts retail outlets.