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Can a leaking valley pan gasket cause small amount of smoke…

Can a leaking valley pan...
Can a leaking valley pan gasket cause small amount of white smoke from the tail pipe when starting the vehicle 2001 BMW 740i
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Answered in 20 minutes by:
3/22/2018
Matt
Matt, Engineer
Category: BMW
Satisfied Customers: 23,488
Experience: Mechanical Engineer with 20 years experience in the auto industry, 8 yrs in formula 1 engine testing
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Hello and welcome to Just Answer

if the gasket leak is allowing water into the engine (as the valley gasket will also seal the water way between the heads) then yes its can create white smoke as a little bit a of water gets into the engine and burns off as steam

it also possible that the white smoke is caused by overfuelling

as this too can create white smoke

so I'd also check for incorrect fuelling due to a faulty water temp sensor. If this is the problem then the ECU will be leaving the car constantly ' on choke' and not reducing the fuelling as the engine warms - so unplug the sensor and clean the contacts on both sides with some switch / electrical cleaner (not WD40) and inspect the wiring for any signs of damage to the insulation especially where it runs over other components and through the bulkhead- if this doesn't help consider replacing the sensor as they're not expensive

Check for exhaust leaks before the O2 sensor as if this has been experiencing an exhaust leak then it will have been running very rich as the sensor will see the extra air pulled in as fresh / lean fuelling and be adding fuel to compensate.

this can lead to catalyst failure as the extra fuel can re-light inside and melt the catalyst

The best way to find an exhaust leak is to run the engine from cold and feel around the exhaust joints with your bare hands - you'll have about 30 seconds before it all gets too hot and you should feel any escaping gas blowing over your fingers

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Matt
Matt, Engineer
Category: BMW
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Experience: Mechanical Engineer with 20 years experience in the auto industry, 8 yrs in formula 1 engine testing
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