I have an knock that occurs only after the truck has been running down the freeway for about 5-10 minutes and it only lasts about 5-10 minutes. If i drive the truck to the store or around town stop and go it will not do it. The knock does not come back the rest of the day either. It is the strangest thing i have ever heard. BTW it speeds up and slows down with engine rpm as well.

Any help would be greatly appreciated.

Thanks

 

What year and model? Does it run sluggish when it does knock? Have you used the screwdriver to ear to hear where it is coming from? Sometimes a water pump or harmonic balancer that has gone bad will knock similar to an engine knock.

 

Mine is almost similar but the noise is like 2 metals grinding with each other. Normally it will start to make noise after 20 minutes of long drive. Then it will continue to make noise until the car will put to rest for at least 30 minutes. My friend told me that it has something to do with my dis-break. The noise is on the driver side by the way.

 

Sorry, The truck is an '05 Silverado HD with the 6.0L

and its definitely not a grinding noise at idle it sounds like somebody hitting a piece of metal with a hammer

No codes thrown btw

 

I've heard AC compressors sound like that. The suggestion of using a long screwdriver to probe different areas is a good one. Just press the handle up to your ear and probe the area you want to check. Works like a charm.

 

Yeah i was thinkin maybe the a/c compressor but i havent had a chance to get under the truck and do that while the truck is making the sound. i wish it wasnt so damn intermittent.

 

My friend it will take some time but once you start to pin point it for sure you will find what it is.