Popping Sound at Highway Speeds

[snelson]

I notice recently when driving at highway speeds (70 MPH or higher), every minute or so, I hear a popping sound from the engine compartment, fairly loud, can be heard above radio. If this were a gas engine, I might call it a backfire, or perhaps a leaking exhaust manifold gasket. The higher the speed the more frequent the popping. At first I thought it may be a loose piece of wiring or some desbris flapping in the wind, but the chassis is clean. The more I listen though it sounds like a small explosion. Any ideas?


1999 Suburban 6.5 stock engine

[noelb]

It could be a sign of a Headgasket problem. A compression test should confirm this.

[snelson]

I will have that tested, but engine was completely rebuilt in March of this year new heads installed, fewer than 6000 miles since rebuild. But anything is possible.

[Bnave95]

And your sure there is no air in the system.

[snelson]

I will look into that as well. Thanks

[Robyn]

Hmmmm
Only at high speed?
I am suspect of an intake valve hanging a bit allowing the equivalent of a backfire.
Could be a failing valve spring. Unfortunately there is no easy magic way to check it out.
If the engine is running fine at lower speeds this would be my best idea.
Let us know.
Robyn

[snelson]

Thanks for your suggestion. The truck will visit the doctor next week. I will give the diagnosis. Thanks