Thunk Thunk

[MWood]

99 GMC Sierra 4x4 - 5.3 / 65,000 miles

 

I am new to this site, but my truck and I have shared many years of good times. Recently, I noticed a noise (aka thunk) coming from what sounds to be my gas tank. It used to happen only after a few minutes after shut off. Now I am noticing it also a few minutes after start up. This is not a continuous noise/thunking/clunking.. just a simple clunk a few minutes after start up and again a few minutes after shut off. It is as though there is a little guy in there, thunking to get out. I do not notice anything else .. other than it is time for some new wheels and tires ;-) Ideas?

[txab]

Might be an emission part. Evap valve and all that.

 

Seems like recall hearing that the emission system can make a little noise

[MWood]

Well, I wonder if it is something to be concerned about. I replaced my fuel pump about five years ago, seems like that same noise came around before the pump failed. Hmmm... maybe I should focus on those new wheels and tires instead -

[Graya25]

I wouldn't think that it would be the fuel pump, when that goes it's more of a whine than a thunk. I'm going to agree with txab on this, it may be an emission part, but not too much to worry about. Check your connections around the tank and emissions system and make sure that everything is tight.

 

I say go for the wheel and tires

[exracer]

what happens if you pull the gas cap right after shutting truck off?......

[kollak01]

could be a broken baffle in the tank.