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Topic: "Bumping" noise from rear offside wheel (Read 1184 times) |
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KeithCEng
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1996 Cossie Saloon
Posts: 55
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"Bumping" noise from rear offside wheel
« on: Mar 19th, 2011, 1:49pm » |
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My 1996 Cossie Saloon has recently developed a regular “bumping” noise from the rear offside wheel which occurs at roughly 2 “bumps” per second. These “bumping” sounds do not become more frequent with increasing road speed but they do become louder. Curiously, the “bumping” virtually disappears when driving uphill and when coasting downhill. Today, my local mobile mechanic replaced the inner and outer CV joints on the offside half-shaft – unfortunately, it made absolutely no difference (except to my wallet, which is now £105 lighter!).
I am beginning to suspect that perhaps this is something to do with the ABS/TCS (although neither system is showing an alarm light, apart from the normal “self-test” for 3 seconds when first starting). Am I right in assuming that the rear hub incorporates a toothed ring for sensing wheel speed and if so, would missing “teeth” on this ring fool the ABS/TCS into causing this problem by initiating “cadence” braking on the road wheel?
Any thoughts please?
Cheers
KeithCEng
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Highlander
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Expert
13 Scorpios, XR4x4, Suzuki SJ413 for off road :)
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Re: "Bumping" noise from rear offside wh
« Reply #1 on: Mar 19th, 2011, 2:21pm » |
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Any ABS or TCS operation should show on the dash warning light, anything wrong with the system would not be affected by downhill or uphill driving.
Is it a constant noise or irregular?
Shocks?
Spring?
Subframe bushes?
diff bushes?
antiroll bar bushes
Get underneath it with a crowbar and see if you can get anything to move 
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on Oct 17th, 2011, 12:35pm, Simmo wrote:I give up !  Too much for an old boy!  |
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Snoopy
Administrator
Very old.BAD tempered and missing friends.
Posts: 6278
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Re: "Bumping" noise from rear offside wh
« Reply #2 on: Mar 19th, 2011, 2:40pm » |
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If it was me I would look very carefully at the rear wheel bearings. When they start tp fail they can generate some random noises. Mine did when they started to fail. As well as checking those other things.
In my experience the only sure way of checking them is to disassemble or at least partially do so, but I am sure others will have more ideas and experiences
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KeithCEng
Junior Member
1996 Cossie Saloon
Posts: 55
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Re: "Bumping" noise from rear offside wh
« Reply #3 on: Mar 20th, 2011, 8:32pm » |
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Thanks to Highlander & Snoopy for their prompt responses.
Highlander asked whether the noise was constant or irregular - It is a constant "bump-bump-bump-bump...." whose frequency does not change with differing road speed; It seems to occur mainly during driving on the flat.
Snoopy suggested the wheel bearing as a possibility - The mechanic did check this when replacing the CV joints and said it was OK (although he didn't disassemble it).
How does the wheel speed sensor operate?
Cheers
KeithCEng
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Highlander
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13 Scorpios, XR4x4, Suzuki SJ413 for off road :)
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Re: "Bumping" noise from rear offside wh
« Reply #4 on: Mar 22nd, 2011, 4:56pm » |
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http://www.fordscorpio.co.uk/abssystem.htm
I think you're up the wrong tree with the ABS theory though
I meant constant as in continuously whilst driving? right from moving off? or does it come and go?
on Mar 19th, 2011, 1:49pm, KeithCEng wrote:| Curiously, the “bumping” virtually disappears when driving uphill and when coasting downhill. |
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That alone would suggest to me a worn bush of some type, the large bush at the front of the subframe or the diff mount bushes possibly? but there are many bushes in the subframe that could be at fault.
What about the opposite? coasting uphill, driving downhill?
Does it do it under acceleration or braking?
My theory is that its not so much the incline making the bump go away as in the tension being placed on whatever is making the "bump"
ie. hard acceleration (or climbing at lower revs) will place more tension on a worn suspension bush.
coasting may result in the same tension being placed but in an opposite movement.
therefore driving along normally may be alternating between the two giving you the "bump"
Big subframe bush is no.2 but I believe these are no longer available?
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on Oct 17th, 2011, 12:35pm, Simmo wrote:| I give up ! Too much for an old boy! |
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KeithCEng
Junior Member
1996 Cossie Saloon
Posts: 55
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Re: "Bumping" noise from rear offside wh
« Reply #5 on: Mar 24th, 2011, 7:56pm » |
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Thanks to Highlander for that input - it is an interesting theory and I shall investigate further!
Cheers
KeithCEng
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Mike H
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Renault Clio
Posts: 2594
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Re: "Bumping" noise from rear offside wh
« Reply #6 on: Apr 3rd, 2011, 4:58pm » |
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Not changing frequency with speed seems to negate wheel bearings et al (?)
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Mike H
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