Strange "Bong" noise

shy_guy0324 · May 9, 2005

Hi..

Just new, and I've searched this forum for this problem but to no avail.

I have a 2000 Chev 1500 regular pickup and a 2001 Z71 extenda-cab. In the last 6 months both have developed a "bong" noise. It sounds exactly like a 50 gallon drum out in the sun. Obviously a piece of sheet metal flexing.

It can happen at any time, while driving, stopped at a light, or just sitting there after a period of time.

I have a client with a 99 Blazer and it does the same thing.

Anyone know what this is and if there is a fix?

Thanks!

facn8me · May 9, 2005

Muffler? The only thing all that has in common is the engine running. Just a guess without hearing it.

SS Crew · May 9, 2005

I have an '04 Silverado 2500 that the dealer replaced my muffler due to this problem. After the work was done a TSB came out that said not to replace the muffler, there are no fix for this problem. Well, this muffler sounded like someone was throwing rocks at the muffler when it heated up or cooled down. It did that for about 5,000 miles, now it's quiet. Now it's time for something a litte more macho sounding.

shy_guy0324 · May 9, 2005

Strange thing is, it will do this long after the muffler is heated up.

This is one big BONG!!! I've never heard a muffler do anything like this... It would have to be a hugh muffler.

Sounds like someone hit a 50 gallon barrel with a bat or sometime.. very low frequency..

SteveCZ · May 9, 2005

I have the same problem in my truck.... I still haven't figured it out.

The only work I've done on the truck is had the fuel sending unit / pump replaced, and replaced the brakes (front and rear) on it.

It started shortly after I had that done.... and it sounds like its coming from the drivers side on my truck, so whether its the gas tank, or my left rear brake rotor / parking brake drum assembly, I don't know. Or it could be something TOTALLY unrelated to that too...

When you find out what it is, let me know

MTmace · May 9, 2005

I have the exact same problem. I thought it was the gas tank but it happens even when I have plenty of gas.

Maybe it is the muffler but it sounds too deep to be the muffler.

Mine vehicle will also make this noise when the vehicle is not running. maybe up to 10 minutes without the engine running.

MTmace

bartlanz · May 10, 2005

My friends and I noticed this around 96, we figured it was becaue they had to make the gas tank a sealed system and inturn the gas tank is creating a bit of a vacuum. when the truck it turned off the vacuum is gradualy leaking.

DEV1ST8R · May 10, 2005

My friends and I noticed this around 96, we figured it was becaue they had to make the gas tank a sealed system and inturn the gas tank is creating a bit of a vacuum. when the truck it turned off the vacuum is gradualy leaking.

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That makes goods sense. I would have to agree.

SteveCZ · May 10, 2005

So, with that being said, did any of you guys who are experiencing this problem have your Fuel Pump or Fuel gauge sending unit replaced? Did it start shortly after that?

Just trying to get to the root cause here. Mine didn't start until I had my sending unit replaced for the fuel gauge. I'm wondering if some vent line got pinched when they put the tank back up in the truck. (cuz they most likely dropped the tank to get the pump out, instead of taking the whole box off).

Is there an easy way to check this, besides dropping the tank ?

shy_guy0324 · May 10, 2005

My friends and I noticed this around 96, we figured it was becaue they had to make the gas tank a sealed system and inturn the gas tank is creating a bit of a vacuum. when the truck it turned off the vacuum is gradualy leaking.

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That makes goods sense. I would have to agree.

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Makes sense for while the engine is off, but both mine do it while driving too, although I only notice it while stopped for a light, or shortly after I start to move.

Neither of my trucks have had work done on the tank or fuel system. Both have had brake work done though.

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JAMIEZ71 · May 10, 2005

It is your muffler expanding and contracting. I had a 96 and have a 2002 and the noise quit when I put after market exhaust on them. I heard it many times after arriving to my hunting location and changing boots at the side of the truck and here the "bong" you're talking about. I have a buddy that has an 00 truck it does it too. The cause is just a large amount of thin metal with no supports inside it.