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        General >> Problems >> FRONT DODGY BRAKES - GRABBING BADLY-THEN RELEASING
        
(Message started by: grandadman on Sep 28^th, 2007, 1:27pm)

Title: FRONT DODGY BRAKES - GRABBING BADLY-THEN RELEASING
Post by grandadman on Sep 28^th, 2007, 1:27pm

This may tie up with the ball joints sited by my MOT tester and posted in a previous thread...
As I brake, no matter haw fast I am going the brake pedal seems to be grabbed and then released causing me some concern ??? It is quite a heavy grabbing feeling at a rate I would guesstimate of once per revolution of the wheel. b.t.w THE BRAKES ARE BRILLIANT!!
It is as if the discs were badly warped but I don't think they are ???
The previous owner passed on a garage bill for rectification of this problem 30/11/2006 for £368.94 [not a Ford dealer] It reads:
REPLACED FRONT PADS AND DISCS, REPACED REAR BRAKE CALIPERS AND HANDBRAKE CABLES AND ONE TYRE. REPLACED HOSE FLEXY PIPE.

Any ideas on this one folks

Title: Re: FRONT DODGY BRAKES - GRABBING BADLY-THEN RELEA
Post by jonnycab on Sep 28^th, 2007, 1:43pm

With warped discs you will tend to get a vibration in the steering when braking, which gets heavier the faster you are going :)

Could be an ABS fault which is causing it to kick in every time you brake :-/

Hope this helps ;)

Title: Re: FRONT DODGY BRAKES - GRABBING BADLY-THEN RELEA
Post by grandadman on Sep 28^th, 2007, 1:53pm

Thanks jonnycab for your input

Can I disconnect the ABS from the front brakes?

Title: Re: FRONT DODGY BRAKES - GRABBING BADLY-THEN RELEA
Post by jonnycab on Sep 28^th, 2007, 1:55pm

Hi there again, I've just read your previous post about the worn ball joints on the wishbones.

It could be the reason for the brake judder, but will also cause generally unstable steering & if badly worn will tend to clonk heavily, especially when turning left or right on full lock :)

Also, if the ball joints on the wishbones are worn, then it is highly likely that the wishbone bushes are worn as well :)

Title: Re: FRONT DODGY BRAKES - GRABBING BADLY-THEN RELEA
Post by jonnycab on Sep 28^th, 2007, 2:14pm

The ABS module has two fuses....F46 & 47 in the battery side fusebox, but I wouldn't like to give advice on disconnecting the ABS, as I'm not sure what effects it will have on the braking system....

No doubt someone else will be along soon to give better advice :)

Title: Re: FRONT DODGY BRAKES - GRABBING BADLY-THEN RELEA
Post by jonnycab on Sep 28^th, 2007, 2:26pm

Just one other thought about the brakes grabbing.........seeing as the car has had all that work done previously on the brakes......it may be an idea to check that the front caliper bolts are tight, as a loose caliper can also cause what you describe :)

Title: Re: FRONT DODGY BRAKES - GRABBING BADLY-THEN RELEA
Post by grandadman on Sep 28^th, 2007, 2:31pm

Hi jonnycab, That idea of yours sound good!!!I will check these calipers bolts tomorrow weather permitting and report back.

Title: Re: FRONT DODGY BRAKES - GRABBING BADLY-THEN RELEA
Post by harry.m1byt on Sep 29^th, 2007, 11:44pm

on 09/28/07 at 13:53:05, grandadman wrote:

Thanks jonnycab for your input

Can I disconnect the ABS from the front brakes?

You seem to be posting in two threads, see my reply to you about a possible solution to the brake judder in the other thread you started.

Regarding the disconnecting the ABS....

One easy method to disable it is to just disconnect any one of the sensors, which will cause the ABS to fail its diagnostic checks at switch on. If the checks indicate a problem the ABS will be disabled. The brakes just behave as normal none ABS equiped brakes then, with the ABS fault light staying on - which is an MOT failure point.

There are plugs under the rear seat for the rear wheels, or plugs just close to the suspension struts under the front wing - just unplug any one of them.

Title: Re: FRONT DODGY BRAKES - GRABBING BADLY-THEN RELEA
Post by grandadman on Oct 1^st, 2007, 7:29pm

All has been revealed by me!!although the car was in today to my local Ford dealer for a 'health check' they didn't site the problem - It wasn't until, by accident I drove away from the local Post Office with the HAND BRAKE not fully released that felt the same effect on the car and braking being created by the hanbrake/rear pads engaging on a really badly warped O-S-REAR! disc and creating this on - off - on - off effect which had me so worried

The more I pulled the handbrake on the worse it got. so I thought ah hah!!! rear brakes not front brakes as I had previously thought ;)

The upshot was, home - both rear wheels off, sure enough running the car in D, on axle stands, no revs revealed a horrible OFF SIDE WARPED DISC I am talking of an out-of-true 2-3 mm that is why the fault was in direct proportion to the wheel revolutions = l revolution of the wheel = a 2-3mm out of true excusion towards to the inner pad creating mayhem I mean mayhem vibrations throughout the car and really worrying.

I am so pleased that even though I am heading for the magic 70 yrs of age I can still get out and get under [carefully] and do my own diagnosis and not be ripped of by our cousins that work in garages who, I believe will take your eyes out and then come back for the socket ;D {no disrespect to you mechanics!!]

I mentioned the bill paid by the previous owner of nearly £400 where the garage last year had misdiagnosed the problem :-/ they should have looked towards the rear end of the car.

I do hope that this episode helps someone else in the future :D I was baffled but I came to the right place Ford Scorpio.co.uk

A final request for help I have the car still on axles stands and I need some advise on pushing the piston back inside the caliper - If anyone can assist I would be most obliged - tomorrow it's source some new rear vented discs and new pads and then onwards and upwards!!

Cheers everyone :D I do hope there are no glaring typos !

Title: Re: FRONT DODGY BRAKES - GRABBING BADLY-THEN RELEA
Post by grandadman on Oct 1^st, 2007, 7:40pm

It is as if the discs were badly warped but I don't think they are
The previous owner passed on a garage bill for rectification of this problem 30/11/2006 for £368.94 [not a Ford dealer] It reads:
REPLACED FRONT PADS AND DISCS, REPACED REAR BRAKE CALIPERS AND HANDBRAKE CABLES AND ONE TYRE. REPLACED HOSE FLEXY PIPE.

Any ideas on this one folks

FINAL NOTE: "It is as if the discs were badly warped" ;) :) :D
I wasn't that far wrong eh?

Thanks to everyone for their help :))

Title: Re: FRONT DODGY BRAKES - GRABBING BADLY-THEN RELEA
Post by Snoopy on Oct 1^st, 2007, 7:49pm

You need to wind the piston back on the rears. You need a special wind back tool they are widley available at local spares/ motor factors . A lot of people use the " cube " which works well as far as I am informed . Have a read of THIS (http://www.fordscorpio.co.uk/rbrakes.htm) it will give you the info you require to do the job.

Title: Re: FRONT DODGY BRAKES - GRABBING BADLY-THEN RELEA
Post by grandadman on Oct 1^st, 2007, 8:35pm

This link and info is brilliant ;)
Once again I must express my on-going gratitude to you -THANX!

Title: Re: FRONT DODGY BRAKES - GRABBING BADLY-THEN RELEA
Post by grandadman on Oct 3^rd, 2007, 7:19pm

Disc Judder problem - Cause/rectification.

Just found this summary regarding the problem I had it's 10/10 CORRECT in my case

http://www.brakepartssuperstore.com/index1.html INEXPENSIVE 24V REAR DISCS etc ;)

Symptoms: Vibrations are felt through the car with a pulsating pedal when braking. If the steering wheel vibrates also, this tends to indicate the problem is with the front brakes.

Cause: Usually due to variations in disc thickness (DTV).

Note: These variations in thickness are usually the result of excessive disc run-out caused by mating the disc to dirty or distorted hubs. When driving (brakes off), the pads are normally in close contact to the disc, however when there is excessive disc run-out the pads scuff the 'high' parts of the disc on every rotation and this scuffing gradually wears the disc thinner where most contact is made.

Imagine a buckled bicycle wheel, the brake blocks would catch the wheel rim (braking surface) at the same 'high' points on every rotation. Disc run-out is similar, but the rotation speeds on cars are slightly quicker and brake pads are far more abrasive than your bike's rubber blocks. So when you have driven 2,000 miles, the pads have scuffed the same 'high' spots over 2 million times. Eventually the disc becomes thinner in 2 parts and causes a judder under braking. Simply replacing the discs without rectification will lead to the problem reoccurring.

Solution: Replace the damaged discs, inspect hubs properly and use a dial gauge to ensure disc run-out is less than 0.1mm (0.004" ) to avoid damaging the new discs. Alternatively the discs, if only slightly worn can be machined on the car so they run perfectly true.

Facts: If you fit new discs and they're great for the first 1,000-2,000 miles and then you start to notice a very slight judder developing, you've probably got DTV caused by run out, this is not covered under our warranty

If you fit new discs and they immediately judder, then it's probable (although very rare) that they have been machined incorrectly or a flaw in the casting. :D

Title: Re: FRONT DODGY BRAKES - GRABBING BADLY-THEN RELEA
Post by grandadman on Oct 3^rd, 2007, 7:19pm

That was my last posting on the matter