W124 Multiple sqeal - turn and straight

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isobars

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300SD'79, E300TD '95, 300TDT '82, 280CE '84, 250L '84, 300SEL LPG '91, 300D '80, 300CE '91, 300E '89
Hi All,

After about ten minutes a high pitched squeal comes from what seems to be front left, varying pitch. Brake and it goes/changes pitch and goes, comes straight back or goes for twenty miles. Turn left during its squeaky moments and it gets worse. I thought it was brakes, but the change of direction noise suggests not. I suppose braking is changing the load as is turning, so is it the BJ's? The ones we don't enjoy.

Cheers and thanks in advance.

Paul
 
Is it a constant noise or is it intermittent, changes in loudness...?

Loose Serp belt? Or a driven pulley bearing on the belt? Waterpump impeller. Can you use the Mechs Steth i.e. screwdriver to the ear to help pinpoint its location...
 
Hi,

It's intermittent, does that rule out the fiddly BJ's?

The belt is tight, and I might say, perhaps a little too tight so I'll step that back later.

The noise always goes if I brake, though sometimes it has to be harder than others, mostly returning immediately. Yesterdays noise log was:
Start and drive six miles, including ten minutes stop, very wriggly roads, no noise, then it kicked in for three miles, then went. Stopped for two lots of shopping, forty and fifteen minutes, no noise. Five miles later, started again, stopped after five.
Passed an MoT last week where the front wheels sit on the moving plates, doesn't squeak when pushed down.
Appears from nowhere on the straight, thereafter can be instigated with a left turn - although I could be on the straight just after a left turn, I'll have to make better notes when I take it out later!

Thanks for your input.

Cheers,

Paul
 
Certainly sounds brake related.

Simple things first:
Anti-squeal pad missing.
Pad seized in carrier due to build up of rust (My favourite).
Caliper slide pins in need of lubrication.
If the caliper was seized then it should have shown up as an imbalance on the mot.

The only way to find out is to remove the offending pads and check.

Tony
 
Hi,

Thanks for the input.

New-ish pads in there, free movement.

I can't see an anti-sq pad. Where is that mounted?

Very shiny discs.

Could a brake problem be intensified by turning?

Cheers,

Paul
 
Anti squeal shims sit between the pad and caliper, they're just a thin metal shim sometimes with a few 'hooks' to clip onto the pad backing plate (more common with floating calipers), other times they're located by dowel pins used to secure the pads instead (how it's done on my 320 with fixed/non floating calipers). Some pads have have them 'built in' as a rubbery pad stuck on the backing plate. Usually but not always they make a bigger difference when using brakes lightly at lowish speed i.e. no noise when driving or braking firmly, squeal/squeak when maneuvering or braking gently from lowish speeds
Floating or fixed calipers there's also some anti rattle springs, if one of them is AWOL or broken pads can move about in the caliper more easily
Anti squeal shims kinda work by dampening/changing the frequency of noise from vibration. The springs kinda help retain pads as well as stopping them from rattling about which can lead to/exaggerate squealing from vibration http://www.w124performance.com/service/w124CD2/Program/Chassis/42-0160.pdf shows the springs on floating calipers. With fixed calipers it's more obvious (fits across the 'pad window' in the caliper after the pads are inserted and the pins hold everything in place) and looks like https://www.google.co.uk/search?q=0...ved=0ahUKEwiikpHusN3PAhVrBsAKHWVvDoMQ_AUIBygC on 124s

Dead/dying lower balljoints more commonly result in creaks when turning slowly over bumps. A lot of MOT testers won't spot knackered lower balljoints (unless the boot is ripped) due to the way the joint is loaded i.e. the way they usually check with prybars won't work due to the amount of preload on it. The special tool shown here http://www.w124performance.com/service/w124CD1/Program/Maintenance/94_95/3355.pdf isn't necessary, the important bit is that you check for slop in a kinda **** about face way to the usual method of using a prybar to try and lever the joint apart to spot excessive movement

My money is on a spring being broken or missing
 
Hi Hotrodder,

Many, many thanks for all the detail in that comprehensive post and for taking the time to compose it.

Excellent reading and advice.

Had a quick ten miles in it this afternoon, plenty of bends and braking - no noise from the wheels, but there's a faint bearing noise from the w/pump - I think, I've taken some extreme tension of the serp belt to see if that's causing it.

I know it will be back tomorrow. I'll do the same run I did on Friday when it last kicked-in badly.

Had the calipers off and the pads are firmly mounted.

Cheers,

Paul
 
Only other thing that might happen with cornering/braking would a change in engine position due to worn engine mounts. This might result something rotating coming in contact with something it shouldn't. The cooling fan and radiator shroud might be candidates?
 
Thanks, Graeme.
It gets very little use, only had three or four hundred miles in the last 12 months and even less over the preceding few years, maybe I'll give it a few hundred or more a week and see if the noise goes after checking your suggestion out.
It's a very shrill noise.

Cheers,

Paul
 
Stone trapped between the backing plate and a front disc

Nick Froome
 
Stone trapped between the backing plate and a front disc

Nick Froome

+1
SWMBO had a brake squeal when turning right which also varied in tone with braking. It turned out to be a trapped stone as Nick describes.
 
Well, that's my favourite!

Off to inspect.

Thanks everyone.

Cheers,

Paul
 

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