Odd sound after shutting off

[bombutt71]

Is there something in the fuel system that would cases a groaning sound to be made after shutting the motor off? It might last 10-20 secs and appears to be from the top of the motor. Thanks

 

[firefighter407]

Maybe the air ride pump?

 

[Racenut]

Is it only when you have been running the A/C? If so it is the rest of the pressurized liquid refredgerant flashing over to a low pressure gas. If this is the case you will hear it next to the fire wall mainly on the passanger side. In other words its normal. Just a thought.

 

[bombutt71]

Nope on both accounts. I don't have air ride and I haven't used the A/C or defrost for months. It is sometimes worse than others and have yet to figure out what I do differently.

 

[Racenut]

Have you done any mods (ie: CAI, K&N drop in, Gotts Mod)? Can you describe the sound a little more, Do you hear it mainly inside the truck or outside? Is it a metalic type of groaning?

 

[bombutt71]

The only mod is 1/2 a Gotts (just removed the silencer). The sound reminds me of some kind of pressure bleed down. I can't feel any vibration on anything I grab. Could it be some kind of fuel return? I couldn't get it to make the sound this morning but I was lucky enough to snap a rusty bolt off on the fog light.

 

[Racenut]

The fuel system typically retains it's pressure when shut off to aid in the next start and to keep from uneeded strain on the pump. It could be a vacumm bleed down. On the back of the Throttle body mount is where all of the main vacumm accesories attach (ie: brake booster, pcv, etc.) How long have you noticed the sound, or better yet could you hear it before you removed the silencer from the air box? With my CIA I always hear the vacumm bleed down now as where with the stock air box (unmodified) I could never hear it, sometimes it is loud and last a good bit others it is so short I bearly notice it. Are you having any drivability issues with it?

 

[97_edition]

The fuel system typically retains it's pressure when shut off to aid in the next start and to keep from uneeded strain on the pump. It could be a vacumm bleed down. On the back of the Throttle body mount is where all of the main vacumm accesories attach (ie: brake booster, pcv, etc.) How long have you noticed the sound, or better yet could you hear it before you removed the silencer from the air box? With my CIA I always hear the vacumm bleed down now as where with the stock air box (unmodified) I could never hear it, sometimes it is loud and last a good bit others it is so short I bearly notice it. Are you having any drivability issues with it?

I agree with Racenut, I got the same noise after installing my CAI. Haven't figured out what is was but haven't experienced any problems either. Noise only last for about 10-15 seconds and just sounds like air releasing on top of the motor, depressurizing? Hope this helps.

 

[bombutt71]

I'm pretty sure it was there before I yanked out the silencer. I'm not too concerned. Thanks for the input. It'll wait until I get back from A-stan if at all.

 

[joezek]

Also check the hose and rubber seal going into your vacuum brake booster. If it's leaking, then you'll have a hissing sound for about 20 seconds after shut down depending on the size of the leak. The booster is like an acumulator and stores vacuum for your brakes.