Skip the auto shop - Our mechanics make house calls

Q: Heavy exhaust smoke on the right side at cold start which disappears after some 15 minutes of motor running

asked by on

At the same time hear a piston knock also at the right side which gradually will also disappear. What could be wrong and how to repair. Thanks for your answer

My car has 30000 miles.
My car has an automatic transmission.

A: Hello. From what you describe, it would app...

Hello. From what you describe, it would appear that your vehicle may be experiencing more than one issue. A common cause for smoke that goes away after a short period of driving is an oil leak.

If one of the engine’s gaskets leaks oil onto the exhaust manifolds it may cause smoke as a result of the oil burning up once the manifold gets hot. The smoke will go away once all of the oil residue is burned up, and will return once more oil has collected on the manifold as a result of the leak.

I would carefully examine the exhaust manifold as well as cylinder head on the right side of the engine for any traces of oil. If you are hearing a piston knock sound that may be a sign of mechanical issues. Usually a knock will be produced as a result of worn pistons, cylinder walls, or bearings, or if the oil is low.

Continuing to drive the vehicle with the engine producing a knocking sound could potentially lead to serious engine damage. I would check the oil to make sure that it is not low, which may be possible if there is a leak. If you’d like to have an expert diagnose the knocking sound, consider YourMechanic, as a certified technician can come to your car’s location to pinpoint the problem and advise you on repairs.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Short Squeaking heard from the engine.

Thanks for writing in about the squeaking sound coming form your 2007 Porsche Boxster. Typically this type of noise is related to a loose alternator or serpentine belt, but commonly appears during acceleration as opposed to deceleration as you're...

Q: Car independently accelerates - 2013 Porsche Panamera

Make sure to stay in touch with Porsche on this issue. It is possible the Idle Air Control valve, which "adjusts" engine idle speed, is faulty, or is receiving an incorrect signal to raise the engine RPM (say for air...

Q: Engine knocking noise in 2003 Honda Civic

A knocking noise is never a good sign on an engine. If the sound appears once, then the engine is started and gets louder when you rev the engine then it may be a rod knock meaning that the engine...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...