Help! Brake pulsing

[Crickleymal]

Vaneo 1.7CDi
I'm getting a variable pulsing through the brake pedal and possibly steering wheel as well. It doesn't always happen and sometimes it's worse than others.
I thought there was some run out on one of the front discs but also noticed a split CV gaiter. The CV joint was practically welded to the drive shaft so the drive shaft has been replaced. The front discs and pads changed as well. The tracking was out and this has been adjusted (once by ATS who only adjusted one side and once by a local tyre place who had to use a blow torch on the adjuster to get it to turn).

The pulsing doesn't feel like the ABS pulsing that you get on a muddy road or on ice, it's slower and obviously speed related. Feels like about one pulse per revolution. I did notice an odd wear pattern on the right hand tyre when it was replaced. The inside edge, which was worn due to tracking, had a regular pattern of highs and lows but this may just have been the tyre.

Any ideas because it's cost me a fortune so far.

 

[OneForTheRoad]

jack it up and turn the wheels slowly , if the discs are run out , youll feel the high spots as they pass through the brake pads. if they are run out , braking will create heat which will make it even worse.

 

[Crickleymal]

I'll try that but as the front discs have been proffessionally replaced (although I am capable of doing them myself) I would have thought it wouldn't be them. The funny thing is sometimes it's worse after driving up the motorway for 10 miles with no braking than it is after driving locally with lots of braking.

 

[OneForTheRoad]

report back with your findings. could be a caliper sticking ?

 

[PobodY]

I did notice an odd wear pattern on the right hand tyre when it was replaced. The inside edge, which was worn due to tracking, had a regular pattern of highs and lows but this may just have been the tyre.

Any ideas because it's cost me a fortune so far.

That sounds like a wheel bearing to me. - It wears unevenly because the tyre is moving laterally.

It could also be suspension related (failed spring or bushing), which has a similar effect.

 

[Crickleymal]

I did wonder about the wheel bearing. I asked the garage to check it out but I don't think they did.

 

[BlackC55]

It still could be the front discs. If the hubs have not been cleaned up prooperly.

 

[Crickleymal]

True but would that explain why it comes and goes?

 

[OneForTheRoad]

True but would that explain why it comes and goes?

No. If it goes away completely .

 

[PobodY]

I did wonder about the wheel bearing. I asked the garage to check it out but I don't think they did.

Could be that the bearing is actually fine, and the hub nut is loose. - Had that on the Nissan, and the fix was to use a 32mm socket and put a breaker bar on it; no more wobbling wheel under braking and acceleration.

 

[Crickleymal]

Ok story so far. I've had all the wheels off and can't see much wrong. No wheel wobble, no bearing play. The front disks and pads are new so the calipers must be sliding freely or else the garage would have said something. The new disks are very evenly worn so I don't think there's a problem with the fitting. Besides it would be odd if the new disks replicated the old problem exactly. All the wheels rotated smoothly with no sticky spots.
The hub nut secures the driveshaft to the hub and again it would be odd if the new driveshaft exactly replicated the old problem.
The rear disks don't seem very well worn. ie. it almost looks like there is little or no brake pressure at the rear because there is rust on the disk and only the high spots are shiny. However I have had the callipers off and checked its movement and the movement of the piston and there is no problem that I can see.
Could it be the ABS? It doesn't seem fast enough but maybe the ABS unit is faulty and that is why the rear brakes aren't applying themselves as much as they ought?

The car's only done 80k miles.

 

[Joderest]

I had a very similar issue with my ML, when braking felt like going over cobbles (how wife described it) I replaced all four discs and all pads, when doing the rears , taking the disc off allowed the linings of the brake shoes to fall to the floor. This could have been part of the issue, the rear brakes had a lot of air, hence braking effort reduced.
Disc's Pads, bleeding the rear and front brakes, replacing parking brake shoes, issue resolved.
They are correct in that the hub face must be very clean, no rust, and i used a wire brush in a drill to achieve that.
Might be of help to you, appears you are half way there already.

 

[wu56Shoozz]

Pulsing is more often caused by:

Siezed Caliper

Or

Warped Disc..

Take it off completely and lay on the flatest surface you can find OR get a rule and skim it over both surfaces (Out & In) looking for Light underneath.. or rocking.. It a Pity your so far away, I have a DTI set up that could look for "Runout" - maybe and just maybe "Toolman" could sell you one cheaply?? Its the only two things that this will be..Thinking: You say that its coming through the pedal but not the steering?? Indicates its the rear discs that are at fault and not the front...possible steering could just be Wheels balancing. Start there first.. then look to the rear..

 

[XJ600]

I'll chuck mt two penneth worth in, check the abs sensor rings (Reluctor ring) in tech speak.
If you have a split ring, (caused by rust build up underneath this happens, they split causing a low speed signal)
Common when coming to a halt, ABS thinks this a wheel is going slower than the rest, ie locked up.
Just a thought from a non plugin 40 year mech.

 

[PobodY]

When do you notice the pulsing? - If it's when you're accelerating or cornering, then that's not brake-related.

My money is still on a suspension issue because of the odd wear pattern you've described on the tyres.

 

[Joderest]

to be honest it does sound like the issue my ML had.
Rear discs were rusty and pads only seemed to be working on about an inch of the disc, this was because there was air in the rear brakes, if you took calliper off, pistons moved ok, it was just trying to compress the air led to very little braking. The new pads are touching right up to edge of disc now, and of course the parking brake linings being detached was not helping.
The symptoms were like the the brakes were causing a sort of bumping feeling, and as wife said, when braking it was like driving over cobbles.
I know how the air got in, and was something to do with the last owner and his choice of garage !!!!!!!

 

[Crickleymal]

Pulsing is more often caused by:

Siezed Caliper

Or

Warped Disc..

Take it off completely and lay on the flatest surface you can find OR get a rule and skim it over both surfaces (Out & In) looking for Light underneath.. or rocking.. It a Pity your so far away, I have a DTI set up that could look for "Runout" - maybe and just maybe "Toolman" could sell you one cheaply?? Its the only two things that this will be..Thinking: You say that its coming through the pedal but not the steering?? Indicates its the rear discs that are at fault and not the front...possible steering could just be Wheels balancing. Start there first.. then look to the rear..

Where are you? We're on holiday in Yorkshire next week

 

[Crickleymal]

I'll chuck mt two penneth worth in, check the abs sensor rings (Reluctor ring) in tech speak.
If you have a split ring, (caused by rust build up underneath this happens, they split causing a low speed signal)
Common when coming to a halt, ABS thinks this a wheel is going slower than the rest, ie locked up.
Just a thought from a non plugin 40 year mech.

No ABS on the rear brakes. ABS rings on front brakes OK

to be honest it does sound like the issue my ML had.
Rear discs were rusty and pads only seemed to be working on about an inch of the disc, this was because there was air in the rear brakes, if you took calliper off, pistons moved ok, it was just trying to compress the air led to very little braking. The new pads are touching right up to edge of disc now, and of course the parking brake linings being detached was not helping.
The symptoms were like the the brakes were causing a sort of bumping feeling, and as wife said, when braking it was like driving over cobbles.
I know how the air got in, and was something to do with the last owner and his choice of garage !!!!!!!

Actually the right rear disc and pad is only worn on one bit. It's as though only half inch of the pad is in contact. Perhaps it is air. I'm loath to start bleeding the brakes now as I could well snap the bleed nipple off.

 

[wu56Shoozz]

Glasgow, Scotland.

 

[Joderest]

Hmm, must confess all brake nipples on the ML were tight, had to file an open ended spanner to make it scrap on fit, then tap that until loose, so can understand your reluctance.