Annoying underbody idle rattle solved.

IdahoDoug

 
 
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Aug 9, 2003
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8,912
My 97 has been making a heat shield like rattle when in D at idle such as sitting at a light. It's muffled and seemed to come from under the passenger's footwell. A month ago I thought I found it because I could duplicated it by slapping the coolant reservoir and it sounded the same, so I put a chunk of foam next to it. Nope, not the problem.

Doesn't do it in Park or neutral - something about the slight load and a warm engine idle.

Finally, I left the truck in D and the parking brake holding it and went over the truck. Found it to be the air intake tube that's inside the right fender where it is sheltered from dust, water and hot underhood air. It makes a sound that fairly replicates a loose heat shield. So I wedged a chunk of foam in there and it has been dead silent ever since. I'll work something out more permanent later.

Just in case anyone else has this....


DougM
 

ERG80

 
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TN
I have a similar rattle but thought it was the passenger side slider contacting the cat heat shield. It wasn't. I will check your idea next. Thanks!
 

Miescha

 
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Jan 12, 2006
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St. Louis, MO
I've got what seems like the same rattle. I put it on the lift and set the parking brake while the tranny was in "D" and I could swear it was the cat shields, but nothing I do there seems to change it.

However, I did find that the rubber mount for the exhaust (the one just behind the factory muffler) is busted - allowing the whole system to bounce up about 1". I haven't confirmed yet, but I was thinking maybe the combination of back pressure at idle was causing the exhaust to vibrate and/or bounce a bit and the exhaust was making contact with the frame somewhere.

I'll check the air intake mentioned here, as I couldn't find anything else.
 
Joined
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Meridian, ID
My 97 has been making a heat shield like rattle when in D at idle such as sitting at a light. It's muffled and seemed to come from under the passenger's footwell. A month ago I thought I found it because I could duplicated it by slapping the coolant reservoir and it sounded the same, so I put a chunk of foam next to it. Nope, not the problem.

Doesn't do it in Park or neutral - something about the slight load and a warm engine idle.

Finally, I left the truck in D and the parking brake holding it and went over the truck. Found it to be the air intake tube that's inside the right fender where it is sheltered from dust, water and hot underhood air. It makes a sound that fairly replicates a loose heat shield. So I wedged a chunk of foam in there and it has been dead silent ever since. I'll work something out more permanent later.

Just in case anyone else has this....


DougM
Yup, I just fixed the same exact thing in the same exact way on my wife's LX. Mine made the most noise when in reverse. It's been bugging us for months. I wedged a piece of rubber between the air intake and the inside of the fender. Stopped it immediately.

Doug, please post up what you end up doing for a more permanent solution, as I am chewing on this right now myself. If I figure anything out, I'll post it as well. Somehow it seems these fine vehicles deserve more than a piece of rubber shoved in.:D

I noticed there is a small Phillips head screw, just out of reach. I think if I could tighten that down, it might do the trick. Problem is, it looks as if I would need to remove the fender to get to it. It is behind the inner fender just enough to preclude getting a screwdriver in there. :hmm:
 
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I know mine (on a '91) are combination of a heat shield rattle at the cat and a worn mount behind cats that allow the exhaust pipe to make occasional contact with the DS union.

The loose heat shield had been fixed once before at a muffler shop with a couple of tac welds. Took all of 5 mins and $20.

But now it's back with a vengence, makes ordering food at any drive-thru a chore. Usually have to shut it down.

But I wouldn't be surprised if the air intake was also another source of noise. If it is, I'd just use some firm foam with a little give to it, like that used to cover a home's exposed water pipes in the winter.
Maybe add a little sealant to keep it in place.
 

IdahoDoug

 
 
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Thermo - my piece of foam fell out, so I'm looking at a solution. Also saw the phillips screw and agree that tightening it may do it.

DougM
 
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Thermo - my piece of foam fell out, so I'm looking at a solution. Also saw the phillips screw and agree that tightening it may do it.

DougM
So, do you think the fender needs to be removed in order to tighten the philips screw? My rubber wedge is still holding strong... for now.
 

little_joe

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Oct 22, 2006
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Holly Springs, NC
I chased this down as well, however mine turned out to be either 1) the radiator overflow tank rattling on its mount or 2) the electrical connectors laying on the passenger side inner fender. I used some foam glued to magnet tape between the overflow tank and the front to stop the overflow tank from rattling, and wrapped the connectors on the fender in foam and zip-tied the foam. Rattle is now gone.
 
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Venice
check the mount for the catalytic converter. Mine was rattling like heck and found one bolt missing and the other real loose.
 
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Kansas City, MO
I to have the same rattle could you please post a pic of exactly where you are taking about. I've looked but not sure I'm on the right spot. Thanks.
 

e9999

You want to do what...?
Moderator
 
 
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Sep 21, 2003
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US
I have a big rattle but I know exactly what it is: the exhaust pipe hitting the Kaymar rear bumper side bracket. It is easy to grind down a bit the bracket but I don't want to weaken it. So I live with the rattle (only at idle). One of these days, I'll put a strong spring to pull on the pipe sideways, that should take care of that...
 

roncruiser

 
 
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Oct 28, 2004
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San Diego
I have something that sounds like a heat shield rattle as well. I noticed it about a week ago. It's gotten a bit louder over the last few days. It happens in D, R, 2, L ...only at idle. No rattle in P or N. I put the truck in D with the parking brake engaged but it's hard to get a general idea where it's coming from. I'll get under the truck the next few days and check things out.

I'll check the following:

Heat shield
Coolant reservoir
Air intake tube inside fender
Catalytic converter mount
Exhaust system in general (mounts, bolts)

I'm glad this thread exists as I had no clue where to start. I'll report back soon.
 
Joined
Dec 17, 2006
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Central Coast, CA
If your foam fell out, put a little glue on it and then slide it back in. My rattle comes from teh heat shield next to the cats. It started after driving in the dunes one weekend. Seems like I slid on the shield and bent it towards the cats a bit. Just grabbed it and pulled it away from the cat and it stopped. usually have to repeat after each trip to the dunes if I climb much
 
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