Constant knocking noise from the rear.., - Alfa Romeo Forum
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Zuhayb
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Constant knocking noise from the rear..,

My Alfa GT appears to make this constant knocking noise from the rear. All suspension has been checked from a specialist, and they couldn't find any fault.

Very, very irritating and annoying when driving on any roads.

Can anyone shed some light?


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I know this may sound obvious but have you checked to see if anything is rattling around in the spare wheel well or the little cubby holes in the boot? When I got mine I had some rattles, the previous owners had spare nuts and bolts kicking around in there!!
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Zuhayb
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I know this may sound obvious but have you checked to see if anything is rattling around in the spare wheel well or the little cubby holes in the boot? When I got mine I had some rattles, the previous owners had spare nuts and bolts kicking around in there!!


I did check but couldn't find anything loose in the boot. I did some further research, and read that the inner rear arches cover appears to be making this knocking noise, which apparently is common.

How true is this?


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Quote:
Originally Posted by LittleGTV View Post
I know this may sound obvious but have you checked to see if anything is rattling around in the spare wheel well or the little cubby holes in the boot? When I got mine I had some rattles, the previous owners had spare nuts and bolts kicking around in there!!


I did check but couldn't find anything loose in the boot. I did some further research, and read that the inner rear arches cover appears to be making this knocking noise, which apparently is common.

How true is this?


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Worth a look, it's a free fix if it is!
I would check that then look at drop links
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Fingers crossed it's a nice simple fix. I've not heard of them making a noise before but every days a school day!!
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Exhaust knocking?
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Zuhayb
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Exhaust seems intact, I even physically moved it but no noise. I will have a look tomorrow and try to identify the problem.


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Exhaust seems intact, I even physically moved it but no noise. I will have a look tomorrow and try to identify the problem.


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Check if inner brake caliper part is moving. I had situation with worn rear discs and brake pads where
calipers produces knocking noise because piston inside is returning back after braking and left space
between.
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Check if inner brake caliper part is moving. I had situation with worn rear discs and brake pads where
calipers produces knocking noise because piston inside is returning back after braking and left space
between.

After some time consuming check, I identified the problem. Both of my rear disk cover/plates are very loose, and screws are missing. I need a set to replace them asap, cause that's what's causing a constant knocking noise when driving on roads.

Can anyone tell me what they are actually called lol? I can't find a set online.


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Lucky it hasn't stuffed your ABS sensors! Are the securing bolts sheared off in the hubs?

To remove and refit the rear disc shields you must remove first the hub with bearing. This is quite likely to damage the bearing and you may also destroy the ABS sensors if their bores are at all corroded.

A cheaper fix might be galvanised baling wire and neutral cure gasket sealant.
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Lucky it hasn't stuffed your ABS sensors! Are the securing bolts sheared off in the hubs?



To remove and refit the rear disc shields you must remove first the hub with bearing. This is quite likely to damage the bearing and you may also destroy the ABS sensors if their bores are at all corroded.



A cheaper fix might be galvanised baling wire and neutral cure gasket sealant.


Touchwood from what I checked there was no physical damage to the abs sensor. There are no bolts screwed on, and the cover plates looks corroded covered with rust.


As for temporary use I'll use the gasket sealant. Do you know the exact name for these cover plates? Hopefully I will replace them as soon someone can help with the name of these covers




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I'd call it a disc brake dust shield. They barely rust here, I will be chucking out two perfect ones next week.
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You can get them from Alfisti.net:
Right side
Left side

You'll need small bolts to hold the plate to the hub too, I think two each side.

The plates are not very expensive however to remove or to install the plates requires removing the wheel bearing. The wheel bearing will almost always be destroyed when you remove them so you need the wheel bearings too.
The other alternative would be to cut away the plate and leave it as it is. Take care not to damage the ABS sensor when you are removing the plate.
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Constant knocking noise from the rear..,

Thanks guys

Removing the plates will cause a lot of hassle, so I will order a set and go to Duncan (Alfanet), and tell him order wheel bearings too






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See if you can have a pair of new ABS sensors to hand, if the supplier will give you 100% credit on return of unopened boxes.
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I would be tempted to remove the old plates first (cut/dremel them off) and then see if it has fixed your noise. If it hasn't fixed your problem then you haven't just wasted 100 on plates, two wheel bearings and labour.

On my track car I'm using some bigger rear brakes and so the disc backing plates have been removed - no problems.
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No plates on my 156 as they turned to dust when fitting new discs. Also can't see how they can make a knocking noise so Pud's advice is sound.
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I went to quite a few garages, and they could not find any fault with the suspensions. The O/S front CV joints are shot, need to replace bushes and front upper arm wishbone had it's fair share. Even then the noise is coming from the rear, I can clearly hear it.

If it's not the plates causing the problem, then what is?


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I went to quite a few garages, and they could not find any fault with the suspensions. The O/S front CV joints are shot, need to replace bushes and front upper arm wishbone had it's fair share. Even then the noise is coming from the rear, I can clearly hear it.

If it's not the plates causing the problem, then what is?


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It may be the plates but a "knock" doesn't make sense as they are wafer thin steel. To confirm cut them off and see if the knock is still there as hub removal is a PITA and may not be necessary. If something was dangerously amiss with the suspension then the garages would have identified it so all you have is an annoying sound.

Roll bar knocks are certainly difficult to diagnose on a stationary car even with access to a ramp. Could be this. You may be able to see evidence of wear the roll bar is touching somewhere.

Have you given the exhaust a good shake if it touches the underside of the car then this makes a very loud and unnerving knock.

Look in the boot. Is there a lose wheel nut in the tyre well? Is the spare secure?

Does the knock present itself on bumps, when cornering or braking, at certain speeds? Is it on one side? Can it be felt through the floor? Has it had any work on the rear done by previous owners?

Basically, I think you can assume it is safe as more than one garage has investigated. It's up to you to decide if you want to throw money at it. To put things into context recently i spent 800 replacing rear suspension components. Not fun.
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Eight hundred! Good grief, I hope you got some nice kit for that figure. Should be almost enough to renew nearly every wear item on the rear end.
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Eight hundred! Good grief, I hope you got some nice kit for that figure. Should be almost enough to renew nearly every wear item on the rear end.
Started needing 2 new shocks ended up replacing everything.

Like most jobs on a 10years plus old Alfa the words "can" and "worms" spring to mind. Or "money" and "pit".

Still love it.
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Edith Piaf sang about it.
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DG I know how you feel...

My Rustbucket is actually at the garage... NSR shock spring plate rust-dropped Tuesday and had to be picked up by them. Luckily it stayed on top of the tyre. I removed the inner linings today in his yard (saves money ) and found... effed top mount sheet metal. The domes are absolutely solid (he poked it THOROUGHLY) but the inner welded sheet metal (that looks like the top of a vase) is totally rusted from the bottom and OSR doesn't look much better. NSR is so bad it is moving about 1/2 inch upwards when the car is released back down.

At least we now have an action plan to keep it on the road... Weld a metal collar in the same shape around it like a neck collar to hold both in place and then replace the shocks...

And no info on yet...

But as my Reg plate suggests... Y xxx TBC -> to be continued

Axel
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After constant annoying checks, and re-checks I finally cracked the F'in knocking noise! It turns out to be my boot, which is fairly loose and moves side to side quiet easily. Also, I realised the boot doesn't shut properly, I have to keep opening and closing the damn thing till its proper shut. What a F'in B!!!

I was completely wrong about the calipers.

How do I tighten up the bolts? What tools do I need?


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My rear end also has a knocking noise and it turned out to be the exhaust knocking on the rear subframe but this wasn't obvious when rocking the exhaust when stationary.
My cure was to use a thick piece of rubber zip tied to the subframe. Nocking noise gone.
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