Technical Flumoxed by clanging rear suspension

[AnthonyH]

The rear suspension on my Grande Punto project car (basically a scrap car) was heavy, and so I decided to "Fix it" You know where this is heading now don't you..

I decided to change the rear shocks. After the change it started to clang very heavily so much worse I wished I hadn't started So I figured I'd bought bad shocks off ebay and replaced them with better ones from GSF. But the car was still clanging, so I changed the rear springs and its still clanging. I then changed the hangars on the exhaust and the same result. I've tied up the heat shields so they can't move much. I checked the rear seats to see if they move but nothing. I took everything out of the boot, including the tyre.

The clanging noise is metallic and occurs going over big speed bumps, its not noticeable on small speed bumps or ordinary driving. It is coming from the rear as I go over the big bumps when the rear suspension bottoms out.

So now I'm at a loss, what can I check next?

 

[GrandePunto PL]

Record this sound.
Are you sure you did everything correctly? All bolts (threads) are OK, they hold parts tightly?
This is simple-stupid setup.

Rear axle bushings and mounts OK?
Brake system too?

 

[AnthonyH]

Record this sound.
Are you sure you did everything correctly? All bolts (threads) are OK, they hold parts tightly?
This is simple-stupid setup.

Rear axle bushings and mounts OK?
Brake system too?

I'll have a go at recording the sound.

The axle bushings look OK, but how do i check them?

What do you mean by checking the brake system? I can't see anything moving.

 

[GrandePunto PL]

What do I mean... I mean you did simple job wrong. Missed something "obvious". It happens (#MeToo).
Something is not tight enough, worn, not sitting properly in place etc. One part, one bolt probably (because rust).

Or mixed sides L/R, shock absorber mounts, but I doubt it would make any noise.

 

[AnthonyH]

I captured a sound while going over two speed bumps. It sounds a lot more metallic in person than it does on this recording.

I can't have mixed up the left or right mounts because I did them separately. It is possible I haven't tightened the top bolts enough, I used a breaker bar and they certainly look flush but I'll recheck them.

I'll get some pictures of the axle bushes as well.

 

[AnthonyH]

I compared the shock absorber bolts on the problem GP with the same bolts on my EVO and they were in a slightly different position, the EVO bolts are about 5mm lower down. So i altered the bolts on the GP to be 5mm lower but now I can't tighten them sufficiently to get the mount flush with the car underbody.

I have an impact gun and a big breaker bar but I can't move those bolts. So stuck again...!

 

[GrandePunto PL]

Redo the whole job (both sides). And think during the process this time (job seems easy, but it's not).
This is not a job for "grease monkey" with an impact gun.
Systems/mechanisms like that require attention to details (cleanliness, final torque up in the air or with the car lowered on wheels, how the parts are sitting in place, how they mate together - you don't force things to fit just by using more torque on bolts).

And yes, I did most possible mistakes in the past (wrong order of operations, too much/little torque, parts dirty/rusted, out of adjustment/position, mixed parts L/R, copper grease everywhere, "cross-threaded" bolts and so on).

 

[AnthonyH]

Redo the whole job (both sides). And think during the process this time (job seems easy, bo it's not).
This is not a job for "grease monkey" with a impact gun.
Systems/mechanisms like that require attention to details (cleanliness, how the parts are sitting in place, how they mate together - you don't force things to fit just by using more torque on bolts).

And yes, I did most possible mistakes in the past (wrong order of operations, too much/little torque, parts dirty/rusted, out of adjustment/position, mixed parts L/R, copper grease everywhere, "cross-threaded" bolts and so on).

I was watching shock absorber replacment videos earlier today, it looked so easy to tighten the bolts...then on the screen came the text "use new bolts". So then I went t ePER to look for the bolts to buy. The cheapest I could find is about £10 delivered for 4 new bolts from the Fiatworkshop website below.

Fiat Grande Punto Shock absorbers

www.fiatworkshop.co.uk

When I've got the new bolts I'll re-do the job and try to get it right

 

[GrandePunto PL]

Look into the axle mounts, the nuts (welded inside the body - pictures in the link), if there is a rust.
https://www.fiatforum.com/threads/2005-uk-gp-1-3-90bhp-rear-suspension-bushes.481155/

 

[AnthonyH]

Look into the axle mounts, the nuts (welded inside the body - pictures in the link), if there is a rust.
https://www.fiatforum.com/threads/2005-uk-gp-1-3-90bhp-rear-suspension-bushes.481155/

I think you're right, there is rust in the shock mount threads!

I cleaned the bolts and got rid of that rust, but didn't clean the mount threads in the body of the car.

I can't access the mount threads directly, this car has a metal panel blocking my way, but i'll re-do the job tomorrow. Thanks!

 

[AnthonyH]

I took off both shocks and mounts. One of the threads was rusted up, so I cleared that, but the clank is still there...

I found a "LH" on the mount which was on the left hand side.

I'll give it one last try next week before concluding its not the shocks, but I'm still stuck with this one

 

[AndyRKett]

You don’t have a lot to explore here, either the lower shock mount, upper shock mount or the axel bushings. If the knock wasn’t there before you did the work then that would tend to suggest it’s something to do with the shocks rather than the axel bushings, that being said the new shocks could have highlighted a problem you’d not previously noted.

These bolts should not be so difficult if they are rusted and need cleaning up then that’s a straightforward thing to do.

Do make sure it’s not something really stupid like something banging around in the spare wheel well boot or rear foot well

 

[AnthonyH]

You don’t have a lot to explore here, either the lower shock mount, upper shock mount or the axel bushings. If the knock wasn’t there before you did the work then that would tend to suggest it’s something to do with the shocks rather than the axel bushings, that being said the new shocks could have highlighted a problem you’d not previously noted.

These bolts should not be so difficult if they are rusted and need cleaning up then that’s a straightforward thing to do.

Do make sure it’s not something really stupid like something banging around in the spare wheel well boot or rear foot well

Thanks for the prompt to have another look at this. The car is safe to drive, and just fine as long as I don't go fast over big bumps, so I've put it on the back burner. I'm going to have another look at the boot and see if there's anything I can see.

Worse case scenario is that in changing the shocks it upset the axle bushings, which i'd have a lot of trouble fixing.

 

[AnthonyH]

Thanks for the prompt to have another look at this. The car is safe to drive, and just fine as long as I don't go fast over big bumps, so I've put it on the back burner. I'm going to have another look at the boot and see if there's anything I can see.

Worse case scenario is that in changing the shocks it upset the axle bushings, which i'd have a lot of trouble fixing.

I re-adjusted the shocks again, its not them.

Is it possible there is something in the body of the boot that is loose?

I took some pictures of the axle bushings, they look OK i think?

 

[GrandePunto PL]

Come on. This is simple, primitive car.
There is nothing mysterious about it (design).
Suspension, brakes, exhaust, fuel system, body/interior parts. That's all (at rear of the car). Those things can make noises.
Messing with suspension can disturb the brakes or exhaust for example.

Bushings are old, but still holding up (kind off). But the amount of rust is not "OK". It should fail the MOT.

PS

The clanging noise is metallic and occurs going over big speed bumps, its not noticeable on small speed bumps or ordinary driving. It is coming from the rear as I go over the big bumps when the rear suspension bottoms out.

So you're saying, you are going over biggest speed bumps, faster and faster, until it finally bangs (shocks out of stroke, limit reached).
And then you're surprised (shocked, pun intended), that there is a noise?! Is this trolling or for real?

Is there a Off-topic or Humor section on the forum? Moderators, move This thread there.

 

[AnthonyH]

Suspension, brakes, exhaust, fuel system, body/interior parts. That's all (at rear of the car). Those things can make noises.
Messing with suspension can disturb the brakes or exhaust for example.

If i knew how to check these i would.

Bushings are old, but still holding up (kind off). But the amount of rust is not "OK". It should fail the MOT.

It had an advisory for rust on the rear axle.

So you're saying, you are going over biggest speed bumps, faster and faster, until it finally bangs (shocks out of stroke, limit reached).
And then you're surprised (shocked, pun intended), that there is a noise?! Is this trolling or for real?

I mean before I changed the shocks I could go over those bumps and there was no no clank, also in my EVO i can go over those bumps at the same speed and there is no clank. Its not a joke and i'm happy to admit i've been a DIY mechanic for less than a year.

 

[AndyRKett]

looking at the general state of the axel in those photos I would be inclined to take it off and attack it violently with a wire brush on a drill. The whole thing needs cleaning up and a new coat of black paint. In doing so I’d replace those bushings, they look shot to me. It could be the forces that the old shocks were not resisting are now being pushed into those tired looking axel bushings.

i'm happy to admit i've been a DIY mechanic for less than a year.

Which is awesome and the entire reasons forums like this exist so people can help each other out

One day someone may have the same problem and when you’ve gotten to the bottom of this, you’ll be able to help that person out

 

[AnthonyH]

looking at the general state of the axel in those photos I would be inclined to take it off and attack it violently with a wire brush on a drill. The whole thing needs cleaning up and a new coat of black paint. In doing so I’d replace those bushings, they look shot to me. It could be the forces that the old shocks were not resisting are now being pushed into those tired looking axel bushings.

I had a closer look at the axel bushings and one of them is a bit frayed at the edge where it covers the bolt, but the rest of it seems ok. I've still not given up hope it is something else because I think the job of replacing them would take me too long.

Which is awesome and the entire reasons forums like this exist so people can help each other out

One day someone may have the same problem and when you’ve gotten to the bottom of this, you’ll be able to help that person out

Thanks for the encouragement!

 

[AndyRKett]

One thing I have experienced in other Fiats is bushing that look ok but the rubber is weak and gives way under load.

You would get it with mk2 puntos the lower or upper shock absorber bushes would be weak enough that the outer metal would make contact with the bolt holding the shock despite the bush looking ok.

you could wedge a pry bar in there and see how much movement is in those bushes see if its likely that on a very hard bump the inner part of the mount could be making contact with the outer part of the axel.

 

[AnthonyH]

One thing I have experienced in other Fiats is bushing that look ok but the rubber is weak and gives way under load.

You would get it with mk2 puntos the lower or upper shock absorber bushes would be weak enough that the outer metal would make contact with the bolt holding the shock despite the bush looking ok.

you could wedge a pry bar in there and see how much movement is in those bushes see if its likely that on a very hard bump the inner part of the mount could be making contact with the outer part of the axel.

I've just had a pry bar around the axle bushes but cant get any metal on metal noises, just rubbery creaks. I don't see what else it could be though, I suppose it needs a big load to make its clanks.

Anyway, at least it is nice and sunny! All i need now is an open top eh? I might take a can opener/angle grinder to the roof if the car gives me any more problems lol.