Rear brake pulsing

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maxstu
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Re: Rear brake pulsing

Post by maxstu »

What a real bummer, Ian. :roll:

BTW this pulsing is affecting just one side of the rear brakes or both sides?
Looking through your last post you state you changed shoes and drums. Then garage changed shoes and drums (so you have a spare set now?) too. Have you measured diameter of spare drum linings at various points to make certain they are completely round?
Cant think what it could possibly be!

Add a bit of handbrake and give it a run for a few hundred feet (or metres in your case) without touching brakes to see what happens. If no pulsing then you know shoes and drums are good. If pulsing then its isolated braking system from equation.

In other words...lve no idea :oops:
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zoona
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Re: Rear brake pulsing

Post by zoona »

tobydog wrote: 19 Jan 2021, 19:52
zoona wrote: 19 Jan 2021, 19:14 The garage as checked the run out on the hubs and they are fine.


What else could be wrong?
- Could it be the original drums/shoes were worn and I have been unlucky to have to new sets that are out of round? (the reason I just bought new ones and didn't get them checked was because the labour to check them is more than a new set)
I wonder if it would be possible to bolt the drums on "inside out" and get a clock (dti) set up to check the run-out.....
 

Funnily enough, that was something I thought of when I got home from the garage today. I was drawing it all out to explain to my wife why it was costing so much money to not fix our van. She asked why we couldn't check the runout on the drums, and I said it was in the inside... But I did wonder if it was possible to flip it.
Was going to drop in tomorrow morning and suggest it.

Thanks for suggesting
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zoona
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Re: Rear brake pulsing

Post by zoona »

Oldiebut goodie wrote: 19 Jan 2021, 19:27 Don't know your engine but my thoughts would be a vacuum leak on the servo.

SP, which is a slightly modified DG for the stupid Swiss market.

My manual is in the van, but going to grab that and see what I can find to change tomorrow.

Thanks
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zoona
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Re: Rear brake pulsing

Post by zoona »

maxstu wrote: 19 Jan 2021, 19:53 What a real bummer, Ian. :roll:

BTW this pulsing is affecting just one side of the rear brakes or both sides?
Looking through your last post you state you changed shoes and drums. Then garage changed shoes and drums (so you have a spare set now?) too. Have you measured diameter of spare drum linings at various points to make certain they are completely round?
Cant think what it could possibly be!

Add a bit of handbrake and give it a run for a few hundred feet (or metres in your case) without touching brakes to see what happens. If no pulsing then you know shoes and drums are good. If pulsing then its isolated braking system from equation.

In other words...lve no idea :oops:


Botth sides, but one worse than the other. I wondered if it was a problem on one side, and it was reading as an issue in the other as an 'echo' of the bad side, but been assured it isn't. That does imply something further back in the system doesn't it? I.e. affecting both sides at the same time.

Yes, I have a spare set... Didn't think I would be able to measure accurately enough with verniers. Will give it a go.

Tried the handbrake and I believe that was also pulsing. But will double check when I go back in tomorrow.

Thanks
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Mr Bean
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Re: Rear brake pulsing

Post by Mr Bean »

Might I suggest isolating each side in turn while the other is stationary. If not on a brake testing machine then by using a hose clamp on each wheel in a careful safety first private road test. This could eliminate any harmonic association between wheels by either mechanical or hydraulic coupling. Getting to be a bit desperate now I'l bet. :(  
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zoona
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Re: Rear brake pulsing

Post by zoona »

Very, very desperate. Particularly with £120 / hour labour rates.

Update:

Checked runout with drums reversed. All fine.

Ordered a new bias valve as that is the next thing back from the rear brakes... As you say, getting desperate.

Should arrive tomorrow with a bit of luck.

I had wondered about of one side was affecting the other. If this doesn't work, that would be a good next investigation step.



And, in case anybody wants new brake backing plates, the jp group ones rub on drums. The he a different shape teases as the circumference. Originals have a U shape, but the jp group ones have a V shape. So they rub. Something else to change.
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maxstu
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Re: Rear brake pulsing

Post by maxstu »

£120 per hour. Effing hell! :shock:
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zoona
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Re: Rear brake pulsing

Post by zoona »

maxstu wrote: 20 Jan 2021, 19:48 £120 per hour. Effing hell! :shock:

This is small two man independent garage as well. Dealers are mental...
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maxstu
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Re: Rear brake pulsing

Post by maxstu »

Swizzleland! :rofl
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zoona
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Re: Rear brake pulsing

Post by zoona »

TL;DR - It was the drums/shoes

Longer version...
Two sets of drums and shoes from a good source still caused the pulsing problems, so we discounted that. Two sets in a row couldn;t be bad, surely?...

I ended up replacing the hubs, stub axles, brake backing plates, brake biasing valve, at vast cost.

Then we tried a set of local drums/shoes that had been machined to match each other, and it fixed it.

So i am now down about £4500 (yes, you read that right) because of some "pooh" drums/shoes.



I then took it to the MFK test (MOT equivalent, but super strict and gov controlled)

  • The good news, it passed.
  • The bad news, it broke down 2 mins after leaving the test centre.
  • The really bad news, a valve seat exploded, and I need a new engine (it could be patched up, but not sure I would trust a repair i.e. , wehre did all the bits from the valve set go? Which one is going to explode next?).
  • The really, really bad news is that I have to replace it with an SP engine, even though a DG is mechanically identical.

it just keeps getting worse and worse. And yet, I still don't want to get rid of it and can't wait until the next time i can use it
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maxstu
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Re: Rear brake pulsing

Post by maxstu »

That plain hurts even just to read. :shock:
Are you naming supplier of rear brakes? Or is the name in previous posts here?

As for engines...are you saying prefix on engine stamp number must be SP?
AJ Simmons has a very well built DG for sale.

viewtopic.php?f=17&t=173465
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zoona
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Re: Rear brake pulsing

Post by zoona »

I don't blame them to be honest, but I am going to drop them a mail to warn them there may be a dodgy batch.

I will say they were jpgroup items, as were the brake backing plates - which were also bloody terrible. The drums rubbed on the plates. Both made by the same company.


I saw that engine, as it seems like the perfect option... But yes, it needs to be stamped SP. Although, I am told that this can be worked around with a grinder and a set of stamps...
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maxstu
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Re: Rear brake pulsing

Post by maxstu »

zoona wrote: 04 Feb 2021, 21:12
I saw that engine, as it seems like the perfect option... But yes, it needs to be stamped SP. Although, I am told that this can be worked around with a grinder and a set of stamps...
I'm sure Andrew would be able to help. :ok  
 
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Stesaw
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Re: Rear brake pulsing

Post by Stesaw »

Blimey that was a rollercoaster I never want to get on!
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maxstu
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Re: Rear brake pulsing

Post by maxstu »

Stesaw wrote: 04 Feb 2021, 22:04 Blimey that was a rollercoaster I never want to get on!

Especially without rear brakes... :run
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