Tap Tap Tap
08-22-2008, 06:23 PM
#1
TECH Resident
Thread Starter
iTrader: (4)
Join Date: Feb 2007
Location: Manassas, VA
Posts: 794
Likes: 0
Received 0 Likes
on
0 Posts
Tap Tap Tap My car has developed a Tapping sound when I start it. It's not an exhuast leak, I've already had one of those and this sounds different. It speeds up with the RPM's. Is there a common peiece in the valvetrain that will fail and cause this?
It did not go away after letting the car idle for 5 mins and driving it around my neighborhood a little bit.
EDIT: Also I've had what people told me was a weak lifter for a while. It's a knocking kind of sound that goes away once the car is warm, it doesn't sound like piston slap to me. My dads truck has piston slap and that sounds much different.
It did not go away after letting the car idle for 5 mins and driving it around my neighborhood a little bit.
EDIT: Also I've had what people told me was a weak lifter for a while. It's a knocking kind of sound that goes away once the car is warm, it doesn't sound like piston slap to me. My dads truck has piston slap and that sounds much different.
08-23-2008, 10:45 AM
#5
TECH Fanatic
Join Date: Apr 2008
Location: Shillington PA
Posts: 1,775
Likes: 0
Received 0 Likes
on
0 Posts
edit: and to the OP if it doesnt go away after its warm, id pull the valve covers and check everything out...
Trending Topics
08-24-2008, 08:39 AM
#8
Staging Lane
iTrader: (3)
Join Date: Aug 2008
Location: Texas
Posts: 54
Likes: 0
Received 0 Likes
on
0 Posts
I've had ticking noises that go away when warmed up. Always sounded like valve train to me. The piston slap noise is a little deeper; doesn't sound like ticking. Well it's hard to describe.
08-24-2008, 09:15 AM
#9
Teching In
Join Date: Aug 2006
Posts: 3
Likes: 0
Received 0 Likes
on
0 Posts
Certain late model vehicles have experienced an audible clattering during cold engine-start that is caused by the piston top striking the cylinder head after combustion chamber deposits build up to a level that exceeds the available clearance between the piston and the head. This clattering is referred to variously as "carbon knock," "carbon rap," "deposit induced noise," and "combustion chamber deposit interference (CCDI)." The audible clattering intensity increases with mileage as deposits continue to accumulate.
Recently, an audible clattering noise has been noticed in some vehicles during cold engine starts, mainly in the U.S. The clattering is referred to by various names, such as "carbon knock," "carbon rap," "mechanical knock" and "combustion chamber deposit interference (CCDI)." CCDI is believed to be caused by the deposit formation in the combustion chamber. In the research described here, CCDI was successfully reproduced in a 2.5-liter multipoint injection engine with a polyolefin amine gasoline additive. It was determined that the CCDI was caused by mechanical contact between the piston top and the cylinder head deposits. The vibration due to CCDI originated mainly at the thrust side of the piston right after top-dead-center on compression stroke and was characterized by a high frequency response.
http://www.sae.org/technical/papers/940385
http://www.circlebmw.com/service/bmw...n-cleaning.htm
Recently, an audible clattering noise has been noticed in some vehicles during cold engine starts, mainly in the U.S. The clattering is referred to by various names, such as "carbon knock," "carbon rap," "mechanical knock" and "combustion chamber deposit interference (CCDI)." CCDI is believed to be caused by the deposit formation in the combustion chamber. In the research described here, CCDI was successfully reproduced in a 2.5-liter multipoint injection engine with a polyolefin amine gasoline additive. It was determined that the CCDI was caused by mechanical contact between the piston top and the cylinder head deposits. The vibration due to CCDI originated mainly at the thrust side of the piston right after top-dead-center on compression stroke and was characterized by a high frequency response.
http://www.sae.org/technical/papers/940385
http://www.circlebmw.com/service/bmw...n-cleaning.htm
Last edited by hardball75006; 08-24-2008 at 09:25 AM.
