Rattling noise from underneath 84 Caprice

moliva1568 · #1 10-31-2007, 02:46 PM

Good afternoon,

I have a 84 Caprice that makes a rattling nosie when I'm driving. Smooth or rough road, it's always there. I thought it might be the old exhaust so that was replaced. No change. When it was changed they told me I needed a new cat. I didn't have the money so i just left it. I just got a new cat, and there still is no change. I'm not very mechanical so it might be something small that i'm missing. It sounds like I'm dragging "just married" cans everywhere i go. Any suggestions as to where I go from here?

silicon212 · #2 10-31-2007, 05:03 PM

I know the sound you speak of, it happened to my car. The EFE heat riser valve, sandwiched in between the passenger exhaust manifold and the Y-pipe, has a butterfly that's actuated by a vacuum diaphragm located just outside of the valve assembly. In my case, what happened is that the butterfly broke off of the shaft at the weld and was free to 'flutter about'. This sounded like a coffee can full of lugnuts being jounced about.

Replacing it with a good junkyard part solved the problem. It's hard to believe that such a small part could make so much noise, but it was the problem, and may be the problem with yours as well. It's not uncommon.

moliva1568 · #3 10-31-2007, 05:26 PM

ok,

I don't know of any of the parts you just named. Sorry but I would need a mechanic for dummies type of book. Who do you suggest I bring it to? A regular mechanic or a muffler shop? Another friend of mine had commented that it sounded like it was coming from the wheels. I don't know how he pinpointed that area and he's no genius when it comes to cars either. Any chance that it might be some part of the wheel? I'm not second guessing you. I just want to make sure that my dollar spent actually cures the problem. Thanks

silicon212 · #4 10-31-2007, 07:32 PM

In that case, you need to take it to someone who can pinpoint it for you. It could be anything, really. The left front caliper on my car has, from the time I got it 5 years ago to now, made noise due to the brake pads oscillating in it. It's a rhythmic click-click-click sound that's dependant on the speed of the vehicle. Loose suspension parts can cause noises - broken or missing end-link bushings are notorious for making a noise that sounds like you're dragging a chain, control arm bushings, as well as shock bushings, can make a rattle or clunking sound.

PeteA216 · #5 10-31-2007, 10:10 PM

Quote:

It's a rhythmic click-click-click sound that's dependant on the speed of the vehicle.

Silicon, my truck does that on the driver's side... it's soft and doesnt seem to be getting worse but sounds just like you described, and in the back of my mind when I hear it gets me worried. Could you explain in more detail what that is specifically? I was worried that a CV joint could have been going, but by now it would have gotten worse.

silicon212 · #6 10-31-2007, 11:34 PM

In my case, it's just looseness in the caliper that allows the outer brake pad to oscillate, or rock back-and-forth, within the caliper as it rides against the rotor. It hasn't caused that side to wear out any faster than the other side, so I don't worry about it.

bobss396 · #7 11-01-2007, 06:20 AM

Quote:

Originally Posted by silicon212

In my case, it's just looseness in the caliper that allows the outer brake pad to oscillate, or rock back-and-forth, within the caliper as it rides against the rotor. It hasn't caused that side to wear out any faster than the other side, so I don't worry about it.

I always use disc brake quiet spray on the back of the pads before I install them. Also on the GM outer pad, after I put the whole thing together, I wedge a chisel or big screwdriver between the pad and the rotor hub. Then I bang down the "ears" on the outer pad against the caliper. As soon as you see it, you'll understand.

Bob

bobss396 · #8 11-01-2007, 06:22 AM

And back to the '84 Caprice rattle. When the car is cooled off completely, get under the car and run your hand over the top of the cat. The outer skin of the cat or the heat shield on the floor pan might be loose.

Bob

bobss396 · #9 11-01-2007, 06:24 AM

Quote:

Originally Posted by silicon212

I know the sound you speak of, it happened to my car. The EFE heat riser valve, sandwiched in between the passenger exhaust manifold and the Y-pipe, has a butterfly that's actuated by a vacuum diaphragm located just outside of the valve assembly. In my case, what happened is that the butterfly broke off of the shaft at the weld and was free to 'flutter about'. This sounded like a coffee can full of lugnuts being jounced about.

Replacing it with a good junkyard part solved the problem. It's hard to believe that such a small part could make so much noise, but it was the problem, and may be the problem with yours as well. It's not uncommon.

My '84 is doing that now. I plan to crawl under it this weekend to at least see if I can take it off for now. It does make a lot of noise!

Bob

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