I have a question about a noise that I here coming from my 2006 Chevy
Silverado 5.3 liter. When sitting at a light or in park idling I
occasionally here a sort of bump. bump noise coming from either under the
truck or dash. At least that's where it sounds like it's coming from while
seated in the truck.
What I'm wondering is can there be air in the cooling system that I'm
hearing burping it's self through the system at idle? It almost sounds like
a vacuum vent door popping shut but I don't have climate controlled
controls, just the standard sliders for temperature, and I don't notice any
change in temperature or in air direction.
When the truck was new I had the dealer replace the thermostat under
warranty as the truck would only get to about 170 degrees and was sucking
gas out of the tank. I'm wondering could they have not bled the cooling
system correctly, and does the 5.3 liter usually require you bleed the
cooling system when opened up? The heat is normal, no cold spots, the
temperature gauge stays steady at 200 degrees when warmed up. It also does
this in summer weather when the heat isn't being used.
I've heard what you describe coming from my girlfriend's 2006 Tahoe.
It also sounds as if it could be coming from under the dash. Her
engine is the 4.8L V8, but I'm guessing, based on the fact that you
hear it too, that it may just be par for the course on these trucks.
Occasionally, right after putting it in Drive and taking off, I'll hear
what sounds like a rubbing, low-pitched squeak. Not sure what that is,
but it also appears to come from underneath the dash.
I hear that same noise as well, at lower RPM, it sounds like air rushing
going through a vacuum motor to me. If you give the truck just a little more
throttle or let off it goes away. That noise doesn't bother me that much,
it's the bump, bump that has me wondering, WTF is that.
Distributor bushings tend to make noise when worn. I've heard most describe
this as grinding noise, which eventually disapate as things warm up.
Not sure if this applies, but its a known source of noise.
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