Chessie

Greetings -

2006 K2500 Suburban, 158K miles, 6.0 L motor - runs perfectly smooth and quite from start-up, but once on the highway for a few miles it will develop a noticeable ticking sound. Once I come off the highway and start driving on smaller roads at lower speeds, the sound will generally go away, though sometimes will still be present for a while.

I've searched and read quite a bit, and hear a lot about trucks that seem to have the opposite problem - that is, tick at start up, but quiet once warmed up. I can't seem to find any info about my issue. I'm thinking it may possibly be an exhaust manifold leak that gets worse with higher temps? Not sure, could just be lifter noise? Carbon build-up?

Anyway, any help or experience with this issue would be greatly appreciated.

Thanks -

-c

Rednucleus

Does the tick change along with motor speed?

Chessie

Yes, frequency of ticking increases proportional to engine RPM. If still ticking at idle its approx 4 ticks per second.

tech2

there were issues with 6L camshaft lobes and lifters.


get a mechanic stethoscope and try to see where the noise is loudest.




if you think its exhaust manifold, look for broken manifold bolts. pull the probe off the stethoscope so just the open tube remains. run the tube near the manifold when the engines idling....if its leaking you will hear air blowing past the stethoscope tube.

Chessie

Gentlemen -

thank you both for your replies. Here's a bit of an update/additional informantion for youL

Yesterday took the truck out for 20 - 25 miles on mixed roads. On the way out, hit highway speeds and heard the tick/tapping sound. Spent a few hours away from the truck. On restart all was smooth and quiet. Decided to drive home at speeds no greater than 50 MPH (may have hit 55 once or twice). Same exact roads and route home, but no tapping noise at any time during the ride. Only other vatiable I can think of is that it was a bit cooler out, so I did not have the AC running. I did flip the AC on for a few minutes, but no tapping. Anyway, is there any possibility the tapping noise I'm hearing is the AC compressor?

Thanks again for your help -

-c

Scotiapilot

had a similar situation and found it was an exhaust leak at the rear and only during hwy speeds would it open up. drive me nuts.