Finding an annoying squeal

[SPendrey]

I know I am asking for advice for an undefined problem, but I'm running out of ideas!  This is the situation on my '94 300Tdi...

• No unexpected noises when accelerating, no noises when turning left/right at higher speeds (30+)
• Squealing, or more a metallic scraping sound at lower speeds when slowing, either by braking or just decelerating
• Noise worsens when turning left, stops when turning right
• Have recently changed both front and back brake discs/pads (noise was there before)
• Noise remains with either front or rear prop removed, so wondered if it was the handbrake?  Applying the handbrake slightly does reduce the noise, so I stripped and checked that (also newish), nothing untoward
• Get a similar but shorter lived version of the noise when driving over a speed bump, so possibly suspension related?

At this point I'm thinking the only things left are some sort of suspension/steering issue, even though the noise is also there when not steering.  Or perhaps is could be the transfer box as it is the only common element when removing props, but why would turning increase the noise?  Maybe the front diff, since that would still be turning (when cornering) even with the front prop removed, but all the liquids are in good shape, no metal fragments etc.  All bushes look OK (although I haven't taken the panhard rod out to check it yet).

Not expecting a clear answer, but what would be your approach to diagnose this?

[L19MUD]

This does not fit with all of the criteria above but the most common thing that makes a noise when turning one way but not the other is a wheel bearing. Also quick and easy to check for play/noise by jacking up and spinning it

 

Not convinced it is the answer but a good one to rule out

[SPendrey]

Ah yes, checked those already!  Having said that, there is no play, but they have been on there a long time.

I think I'll strip back and reinstall both front spring/shocks as I think the noise is coming from there.  If I rock the vehicle I can hear a similar noise coming from the front left (I think!).  I have spring spacers on there too, and I reckon I might have a washer rubbing or something like that?

[L19MUD]

1 hour ago, SPendrey said:

Ah yes, checked those already!  Having said that, there is no play, but they have been on there a long time.

I think I'll strip back and reinstall both front spring/shocks as I think the noise is coming from there.  If I rock the vehicle I can hear a similar noise coming from the front left (I think!).  I have spring spacers on there too, and I reckon I might have a washer rubbing or something like that?

if something is moving that should not you will probably see the rusty mark

[MuddyWinny]

In case it helps I have had partially seized (or sticky) brakes cause a squeal (although on a different vehicle).
In my case it was the pads stuck as opposed to the piston in the calliper.

As above, it doesn't really fit with the criteria and you have already changed the pads.

Does the squeal change the harder you brake?

 

[SPendrey]

3 hours ago, MuddyWinny said:

In case it helps I have had partially seized (or sticky) brakes cause a squeal (although on a different vehicle).
In my case it was the pads stuck as opposed to the piston in the calliper.

As above, it doesn't really fit with the criteria and you have already changed the pads.

Does the squeal change the harder you brake?

 

No, no change at all.

I should find time tomorrow morning to take a look at one of the two shock/spring arrangements.  I'm hoping to make progress as so far everything I've done has made no difference at all. 😞

[Bowie69]

I had something like that..... turned out the top of the shock turret had detached, and you couldn't see it at rest, if you bounced the car, the top of the turret would disappear into the turret along with the damper....

Did squeak, took a while to realise what happened 😳 

[Alsace_rangie]

Also check the dust/mud guards on the discs. Maybe got bent out of place when you did the pads?

[simonr]

Over the years I've had lots of mystery squeaks, rattles & squeals.  My method for finding them has been to strap a GoPro (or similar) close to where you think the noise is coming from.  First narrow down by the amplitude - then, if you're lucky, you'll be able to see something moving that shouldnt - or at least, what is moving when the noise ocurrs.

The most mystifying for me, was a squeal, followed by a tinkling noise when cornering or braking.  It turned out to be one of the washers on the back of a worn out front radius arm chassis bush.  The bush was compressed, making the squeal then the washer was loose on the shaft and made a tinkling noise.  When stationary, everything felt tight.

Another one was the 300Tdi fan belt idler bearing which made a dreadful squealing noise, but only on braking for some reason.

[Nonimouse]

I had an annoying click on braking and accelerating. Changed the drive flanges - still did it. Aftermarket Brake Pads (EBC)were moving slightly, back and forward, as the pin/spring set up wouldnt hold them in place. Knocked up some stainelss tube sleaves for the pin/spring - sorted

[SPendrey]

Well, this is embarrassing... I think the cause might have been stones trapped in between the shock washers and the spring seat area.  Although there were also signs that a shock washer was rubbing the spring retainer, so I might put it down to that because it sounds like a more plausible reason!