Strange noise then poof...gone

Soooo... Tuesday night I was driving on 19th Avenue in San Francisco when I noticed a strange rattling sound coming from what sounded like the drivers side of the truck. It was intermittent and I couldn't reproduce it when I tried. It was subtle that night and I kinda shrugged it off.

Yesterday I drove from SF to Redwood City (~20 miles) without issue, but when I went to lunch my truck sounded like a mix between a rattle and a grind. Kind of like a coffee can was tied to the underside of the truck. It didn't affect the drivability, though. Everything about the truck seemed fine except for the noise. It was sporadic too. Sometimes it would go away for 5 seconds, but usually would occur when I let my foot off the gas. For a time it sounded like it was related to an increase in RPM, but not all the time. The noise would not occur if I rev'ed the motor at a stand still. Only when the truck was moving.

Anyway... left work early to take the truck to my mechanic (Toy Shop) in SF and the noise vanished while on the freeway. Like completely. I drove it for an extra 45 minutes trying to get it to come back...nada. This morning I thought I heard it again while getting on the freeway, but I can't confirm it was the same.

After thinking about it some more, I realized that on Tuesday I drove over something that made a funny sound. Like my tires kicked something up and hit the underside. Has anyone ever had something kicked so precisely that it caused a noise like this to occur?

What would you do in my shoes. Should I take it to my shop and have them thoroughly inspect it? Or just keep driving it until the noise comes back (if it comes back...)

Thanks

 

Check for a broken coil spring. They make very weird sounds when the coil rubs against itself.

 

Turn up the radio?

Seriously though, did you crawl under there and spend some time looking around? If you think something hit it, start there. Also, look for loose (or now missing) heat shields around exhaust areas. Check all your hangers, and fuel tank attachment. To me it sounds like you may have been dragging something, then it detached.

 

I had a rattle coming from my catalytic converter for the longest time. It would come and go at random. One day it got louder and louder then vanished and never came back.

I pulled off the cat later and there wasn't anything loose inside, so I'm not really sure what happened.

 

Sounds like maybe a heat shield on the exhaust. You can poke them with a screwdriver or something and see if any of them have excessive movement.

 

might have picked up something that got wrapped around the drive shaft or the heat shield got knocked loose

 

Or there is a gremlin hiding on your skid plate. All kinds of junk gets hucked up there if you have meaty tires

 

Hey all! Thanks for all the suggestions. Today on my way to work the noise came back a little bit. Enough to know that whatever it is didn't "fall off". I haven't had a good chance to get under the truck yet but will be tomorrow. I'm thinking that all of you saying it's a heat shield are probably right. The noise is tinny and inconsistent, so probably rattling when the truck is at a certain "frequency". Anyway, I'll check it out tomorrow and get back to all of you. Once again, thanks!

 

Coils are totally fine. Wouldn't there be a noticeable sag if this were the case?

 

I didn't notice any on mine. Of course I wasn't looking for sag.

 

x2 for looking at exhaust heat shields, when its cooled down try tapping along the exhaust with a rubber mallet and see if you can replicate a noise

I had a heat shield hairline crack on my DS exhaust manifold, it would appear at somewhat random times within a certain rpm range and bounce noise all over the place

 

Good call. The noise also only appears to be happening when the truck is cold. I'm optimistic now!

 

Fingers crossed for you that it's simple and easy to find! Let us know how it goes!

 

Yeah, the metal heats up and expands and quiets down the noise. Definitely sounds like a heat shield to me now. Shouldn't be too hard to fix, you can use a stainless hose clamp to tighten the shield back down, if that's what you end up finding.

 

my upper Cat heat shield "lost" 2 of the 3 bolts holding it on (yay rust) so it intermittently rattled. I just took a small nut/bolt on one of the open spots and tightened it up.

 

If it's the lower cat, I use a cat clamp ever since mine was stolen 5 years ago... I hope I dont have to pull it off...

 

Soooo... it was the catalytic converter. It looks like someone may have tried to unbolt it because 2 of the bolts were pretty loose. I think once they realized the cat clamp wasn't going to let them get it, they gave up. Now everything is buttoned up and the truck is working great again. Thanks for the tips everyone! Glad the "fix" didn't cost me anything.

 

Thank you for the follow up.

 

Awesome dude, glad to hear it. Thanks for replying back with your 'fix'.