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Severe rattle and slamming...


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I'm about to bring the Eldorado in for an early-spring visit to the mechanic, just to have some annoying suspension and exhaust rattles addressed. Having new sway-bar links put in, and a 4-wheel alignment that's long over-due. I have one noise that nobody can get to the bottom of, and it's really started to drive me nuts.

When accelerating hard from a stop, there's a *severe* slamming sensation that feels like it's coming from under the center console area, near the firewall.(Almost feels like somebody's whacking the under-body right under the shift-lever area with a huge hammer). It can be so bad that I'd almost describe it as a wheel-hop, as the entire steering-column will shake violently if I don't back off the throttle.

This only happens when taking off from a stop quickly and hard, but can also be felt by power-braking the car to 2500-RPM or so. I'm assuming it's the exhaust contacting *something* under the car, but nobody can figure out what or why. I've brought it in twice already, but no luck fixing it to this point.

I'd love any insight...

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Have your motor mounts checked if they haven't been already.

I just had my sway bar links replaced on Saturday to rid myself of a front end clunk. It was a major PITA to get the old ones off.

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The motor mounts are a good place to start, my front mount was pulled apart and it created many problems on acceleration and braking. I even got harmonic vibration from the road that travelled through the steering wheel to me. Also, if you have the two dog bones check those for bad bushings, bad bushings allow the engine to move for an aft at the top.

I would also check to see if you have an out of round tiire plus a strut that is bad. If a strut is bad whereas it does not dampen the wheel movement, due to the lack of dampening, a slight bump combined with the acceleration can create a harmonic bouncing in the wheel, wheel hop as you mentioned.

But check the mounts first, get a good light and get under the car in the front, remove any air deflectors that are in the way and look at the front mount behind the radiator to the left of the oil filter adapter, you also might be able to see it from the top, but I get my best view from the bottom.

PS, all left right perspectives are from the drivers perspective

I recently posted a diagram showing their locations, there are 4 mounts front rear and one on each side plus the dog bones at the top.

See Post #12 in this thread, I took photos of my front mount

http://caddyinfo.ipb...showtopic=19074

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The motor mounts are a good place to start, my front mount was pulled apart and it created many problems on acceleration and braking. I even got harmonic vibration from the road that travelled through the steering wheel to me. Also, if you have the two dog bones check those for bad bushings, bad bushings allow the engine to move for an aft at the top.

I would also check to see if you have an out of round tiire plus a strut that is bad. If a strut is bad whereas it does not dampen the wheel movement, due to the lack of dampening, a slight bump combined with the acceleration can create a harmonic bouncing in the wheel, wheel hop as you mentioned.

But check the mounts first, get a good light and get under the car in the front, remove any air deflectors that are in the way and look at the front mount behind the radiator to the left of the oil filter adapter, you also might be able to see it from the top, but I get my best view from the bottom.

PS, all left right perspectives are from the drivers perspective

I recently posted a diagram showing their locations, there are 4 mounts front rear and one on each side plus the dog bones at the top.

See Post #12 in this thread, I took photos of my front mount

http://caddyinfo.ipb...showtopic=19074

Not trying to impose on someone else's thread here, but reading through the thread you linked to, I think I may have to re-evaluate my motor mounts. Yours were cracked on the top and when I checked mine I couldn't see/feel the top, and I still have a mild clunk. I figured if they were going to crack it would most likely be where I could see it. Thanks Mike.

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I'm about to bring the Eldorado in for an early-spring visit to the mechanic, just to have some annoying suspension and exhaust rattles addressed. Having new sway-bar links put in, and a 4-wheel alignment that's long over-due. I have one noise that nobody can get to the bottom of, and it's really started to drive me nuts.

When accelerating hard from a stop, there's a *severe* slamming sensation that feels like it's coming from under the center console area, near the firewall.(Almost feels like somebody's whacking the under-body right under the shift-lever area with a huge hammer). It can be so bad that I'd almost describe it as a wheel-hop, as the entire steering-column will shake violently if I don't back off the throttle.

This only happens when taking off from a stop quickly and hard, but can also be felt by power-braking the car to 2500-RPM or so. I'm assuming it's the exhaust contacting *something* under the car, but nobody can figure out what or why. I've brought it in twice already, but no luck fixing it to this point.

I'd love any insight...

Been there! The best (and probably the only) way to "see" the source of the noise is putting the car on the hoist and powerbraking it carefully while someone is under the car watching the movement of exhaust system. It took two seconds to "see" the source of the noise which was driving me nuts for two years... at acceleration and moving up a hill from a stop.

The saddest thing in life is wasted talent

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Thank you all for your input! I had the motor mount (lower) replaced when I had the engine out for the HG job. Not that it still can't be the culprit. The upper dog-bone mounts were replaced a few years back, but the rubber in them does look "stretched" and out of whack, but not torn yet (but still suspect).

There does seem to be a bit of "play" in the drivetrain, as it feels like the powertrain shifts more than it should when going from reverse to drive.

My local mechanic is a great guy, as he's incredibly honest, but only likes to replace parts if they're truly broken. He doesn't mind clunks/rattles, and usually tells me to "deal with it" when the brakes are mildly warped. While I love his cost-saving approach (as long as it doesn't affect safety or drivability), I want all my creaks/rattles/vibrations fixed once and for all!

I figure I'll print out this entire post and leave it in my car when I bring it in for service! ;)

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Can it be a loose or worn caliper. sometimes they just don't fit right, or have too much wiggle room, and they "clunk". I know when that happens, it can be felt in the steering wheel. Let us know how this issue works out.

Brake pads can do that. It is easy to check by pressing brake pedal when driving over road irregularities. Then brakes are applied the pads cannot move freely up and down and will not clunk.

The saddest thing in life is wasted talent

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Curiosity got the best of me last night, and I popped open the hood and did some light power-braking. The engine had a minor 'rock' going from drive to reverse, but nothing out of the ordinary.

However, when I power-braked while in drive, the front-passenger's side of the engine was SERIOUSLY rising up and out of the engine bay! The right-side (shorter) dog-bone mount was really getting a major work-out keeping the engine down.

I'm not sure of what significance this may be, but I don't think the engine is supposed to be moving around THAT much! (Am I wrong?)

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Curiosity got the best of me last night, and I popped open the hood and did some light power-braking. The engine had a minor 'rock' going from drive to reverse, but nothing out of the ordinary.

However, when I power-braked while in drive, the front-passenger's side of the engine was SERIOUSLY rising up and out of the engine bay! The right-side (shorter) dog-bone mount was really getting a major work-out keeping the engine down.

I'm not sure of what significance this may be, but I don't think the engine is supposed to be moving around THAT much! (Am I wrong?)

How much is SERIOUSLY? 1/2" or more?

The saddest thing in life is wasted talent

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Well over a half-inch. I'd say the engine is really "swiveling up" on the right-side dog-bone, easily a couple inches when power-braking. The slamming sound/feeling occurs when power-braking (at a full-stop, of course), which tells me that it's most likely the exhaust system contacting something, and not a rotating chassis part (axle, etc.)

Now to figure out what mount/apparatus decided to go home early on me... :-/

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If the engine is jumping toward the front of the car, it's most likely the passenger side and/or rear motor mount. I would definitely check all of them out though.

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