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Discussion Starter · #1 ·
Hey everyone,
I realize this is a long shot but here it goes. Ever since I got my manta it has made a clunking noise in the back of the car when ever it goes over a big bump or dip-usually around town. it's the kind of noise you would expect if you left a tool box in the trunk and all the tools flew up inside the box and then land (yes I did remove evereything from the trunk in case that was it). The noise happens not when the car lifts up but when it "lands" after the bump. It seems to happen more when both wheels hit a bump at the same time or when there is more weight in the car. When you push down hard on the rear of the car and bounce it there is no noise. I've been under there several times and can't find any sloppy bushings or loose bits at all. I really don't know what to check next can really worn shocks cause this -when you push down hard on the rear of the car and bounce it there is no noise. Anyone out there with a similar experience?? Any suggestions? please I'm desperate
 

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boomerang opeler
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have you checked to see if the top damper mount is tight as this can give a noise when loose
it needs to have 11 millimetre of the thread and leadin exposed when its tight
if you take the damper off do it with the wheels on the ground or the axil supported on stands so the axil dose not drop
all suspention needs to be checked with weight on so the bushes are in there normal state if you just jack up the car all the weight will just sit on the bottom of the bush so it feels tight
 

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first of all nice opel:p , and do you think it could be rear wheel bearings that are worn but arent worn enough to clunk all the time? (its a long shot but its worth a look)
 

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Discussion Starter · #4 ·
Thanks for the replies,
By top damper mount do you mean the shock absorber right?-I'll check it,- also I checked with the car on ramps so the suspension was weighted, I don't think it's the bearings either since the car only has 40k original miles! -any other ideas out there?
Thanks again
 

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I'm not too sure about the Manta, but here's my 2 cents worth. Check the mounting straps on the gas tank, if they are loose or broken, you'll get the same sounds as you described and won't be noticeable until you physically check them. HTH.

Ron
 

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Do you want the common or obscure possibilities? I've seen many of them over the years. Here are some things to check:

>Worn and/or broken torque tube bushing components.

>Loose torque tube-to-rear axle bolts.

>Bend panhard bar and/or loose exhaust hanger...exhaust strikes panhard bar under compression, or possibly even the sway bar.

>Obscure: Previous owner put brake hose clip on torque tube in the wrong place (top instead of bottom)...brake line strikes floor of car.

>As mentioned above, check for loose shock bolts.

Bob
 

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Discussion Starter · #7 ·
OK,
I checked the shock mounts and they look good. The torque tube bolts "look" tight but need to be checked with a wrench. The panhard bar looks straight too. I like the exhaust angle, the ruber donuts are pretty strechey and I think some are gone but I'll have to try and anchor it a little better and see what happens-I think the tail pipe may actually be hitting the underside of the car on the rebound. I also noticed that the passenger side rear brake line is in contact with the lower control arm though the spring looks like it is correct.
Thanks again for the ideas-it's just what I needed to get me going on this one-any more obscure clunking noise stories are more than welcome!
 

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sleeper said:
OK,
I also noticed that the passenger side rear brake line is in contact with the lower control arm though the spring looks like it is correct.
That is the brake cable for the emergency brake. I was referring to the hydraulic line and hose that travels along the center torque tube. That hose is supposed to be bolted via a bracket to the lower passenger side torque tube-to-rear axle bolt....sometimes people move it to the upper passenger side bolt, and it strikes the floor. Like I said, it's kind of obscure, but I've seen it happen before.

The exhaust definitely sounds like a possibility though, it may be hitting the rear trunk floor.

Bob
 

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Discussion Starter · #9 ·
Ok,
The e-brake wasn't making the noise-I zip tied it in place and it still clunks, I'll check the actual brake line tonight and get a wrench on the torque tube. I'm trying to figure out how to keep the exhaust from bouncing up-all the hangers keep it from falling down. I'm still wondering if really old shocks can be noisy?-I'll be replacing them anyway but like a more targeted approach. I'll let you all know when I figure this out.
 

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While the rubber hangers keep the exhaust from drooping excessively, they can and do get stretched with time, and can sag and lose tension.

But for keeping the exhaust from striking the body during upward movement, Opel used rubber extrusions which fit into small receiver channels in the floorpan just above the front muffler and rear resonator. There is the possibility one or both of these has decayed and fallen out.

Having stretched hangers and no upper bump stops can create more vertical downward movement than usual, and then when the muffler travels upward, it would be hitting directly on sheetmetal, making quite a racket.

"I'll check the actual brake line tonight and get a wrench on the torque tube. "

Keep in mind the torque tube bolts are a metric internal 12-point bolt....., you need the special 8 mm socket for this.

Bob
 

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Don't forget baz's comment on the rubber stubbers. I'd also look to replace those rear shocks. They should not let your drive up that fast over pot-holes.
my 2-cents.
 

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Discussion Starter · #12 ·
I like the exhaust theory more and more hopefully that will pan out-and hopefully ogts has those extrusions if that's it, I do have the special bits to tighten those bolts-though I imagine they would have to be pretty loose to cause much noise.
 

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I know this sounds stupid, but i had a clunking noise in the back and later found out i forgot to put the two screws that hold the bumper that attach at the rear so the bumper was swinging on the bolts at the sides. :D

Btw. why do so many people have those huge bumpers on their Mantas? its a pretty car otherwise, but those bumpers.. eeewwghhh.. horrible!.
 

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Sven;
That's the "Americaniztion" version of the Manta, the Ascona Sedan and Voyage "Sportwagon" we call it here, were required by US DOT (department of Transportation and Safety mandated that these bumpers be used on the 74-75 imported Opels to be sold in the US. I like the Mantas either way, but, the Asconas definitely look better with the US bumpers.
Gene
 

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Another thing to try: if your Opel is typical of US Opels the underside is fairly rusty and/or dirty. Get the car up on stands and get under it with a strong flashlight and look for "clean or shiney" spots where the item is hitting. Under a strong light it should stand out. If not, try coating the upper surfaces of things that may go bounce with either chalk or some grease. Drive the car and get it to bounce. Then get back under it and look to see what item left it's mark on the underside.
Good luck and let us know what you find out. By the way, you have a nice looking Manta! :)
 

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This is a real long-shot and looking at the beautiful picture it probably doesn't apply: if the window seals are severely hardened the rear window can start rattling inside the seals. Driving over a bump makes a sound similar to what you describe.
Ask me how I know.
Thomas
 

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Discussion Starter · #17 ·
Alright,
I got it! I think. It turns out I was having tire clearance issues. I installed wider wheels and the tires just clear the inside of the fenders, but I noticed a very slight wear line on the outside side of the rear right tire-right where it is widest-turns out that it was touching so little that I couldn't hear it when I rocked the car up and down to check the clearance, but when the wheels are spinning it would hit and make all that noise. So I rolled the inside lip of the fender back last night to gain some clearance and viola!
Thanks for all of the tips, I was sure it was something under the car, at least I know my track is as wide as it can get without flairs. Thanks again, if it weren't for this board I would be truly lost!
 
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