Mechanics

Exhaust Pipe Smoke - White

Easy step by step guide on why an automobile would omit white smoke or steam from the exhaust tail pipe, this information pertains to all internal combustion vehicles.

Step 1 - White smoke is a normal bi product of the combustion process, when the exhaust system warms up it evaporates the water before its seen. Before the exhaust is heated by the engine combustion process a small amount of steam will be emitted.


Evaporated Water

Step 2 - When an excessive amount of steam or smoke is present and stays with the vehicle as the engine warms up coolant is being allowed to enter the engine combustion process.


White Smoke or Steam from Tailpipe

Step 3 - Some intake manifolds distribute coolant into and throughout the cylinder head(s). If the gasket that seals the intake manifold to the cylinder head fails it can allow coolant to enter the intake port and then into the combustion chamber. Once the intake manifold has been removed inspect the gasket, if the gasket has rotted or has dilapidated areas between the intake port and the cylinder head it could allow coolant to transfer into the cylinder intake port. Learn more


Intake Manifold

Step 4 - When coolant is in the combustion chamber and the intake gasket is okay, the engine must be further disassembled to locate the failure. Coolant is circulated from the block through to the cylinder head(s). A headgasket is used to seal the cylinder head(s) to the block, when this gasket fails it can allow coolant to leak into the engine cylinder combustion area causing a constant stream of smoke from the exhaust pipe.


Coolant Ports

Step 5 - A cylinder head is constructed of machined aluminum and is susceptible to cracking when over heated, when replacing a head gasket be sure to have the head pressure tested for cracks on internal and machined surface areas, also have the head re-surfaced to help it seal evenly with the head gasket and engine block.

Helpful Information

The amount of steam produced from the tail pipe while the engine is cold varies due to outside temperature and humidity. Coolant/antifreeze is used to cool the engine during normal operation. If coolant is allowed to enter the combustion chamber, the engine will burn the coolant creating white smoke and steam. When this white smoke/steam is being produced it will be accompanied by a sweet, pungent odor and sometimes engine overheating. This condition will also be accompanied by engine coolant loss with no visible leaks.

Combustion chamber coolant leaks can be tricky because the repairs can overlap, and its difficult to know which one it is before dis assembly. Example: A repair shop has determined coolant is entering the engine combustion chambers, as they disassemble the engine they discover the intake manifold gasket failed. It's up to the honesty of the repair shop to alert the customer the repair will be less than quoted.

Or the opposite can happen.

Example: A repair shop has estimated a blown head gasket replacement job, once the dis assembly is complete they inform you the head gasket is okay, they sent the cylinder head out for testing and its okay as well. This only leaves the engine cylinder block as the failure, and must be replaced to repair the problem, and that is costly (new engine in most cases).

AUTHOR


Written by
Co-Founder and CEO of 2CarPros.com
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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Article first published (Updated 2015-05-13)