Post Reply

Brake pad/disc squeal

User avatar
Post by stuartbyng » Subscribing Member » Thu Jun 14, 2018 8:27 pm
Joined: Fri May 11, 2018 8:50 pm
Posts: 6
Hi,

I have a 1986 CF2 250P with the 2.0T engine. The problem I have is a squeal coming from the front brake pads/discs. It did not have this problem until I changed the pads (Ferodo). Since then, despite fitting a new pad fitting kit plus anti squeal goo, they always squeal. I have since changed the pads again (EBC) but the problem is still there. Does anyone have any ideas on this as it is driving me mad!

Thanks,

Stu

Re: Brake pad/disc squeal

User avatar
Post by Phil Bradshaw » Club admin » Fri Jun 15, 2018 6:38 am
Joined: Sun Sep 02, 2012 7:15 pm
Posts: 3579
Possibilities -

1. Excessive front wheel bearings end float: adjust until all free play at wheel rim just disappears.

2. Caliper pistons not moving evenly enough to apply equal pressure both sides of the disc. Hard to determine unless old pads were wearing unevenly -

Image

3. Contaminated pad friction material. Scrub off flat on water-wet ~100 grit wet and dry paper.

4. Pads fitted upside down and jamming in the caliper.

Image

5. Damper springs (2) under the retaining pins (1) incorrectly fitted; what they should look like -

Image
  • What is real is not the external form but the idea, the essence of things. Constantin Brâncuși

Re: Brake pad/disc squeal

User avatar
Post by stuartbyng » Subscribing Member » Fri Jun 15, 2018 8:00 pm
Joined: Fri May 11, 2018 8:50 pm
Posts: 6
Hi Phil,

Thanks for the comprehensive reply. As far as i can remember (I changed them last year) the old pads were wearing evenly, so that should (hopefully) rule out #2.
I have cleaned the friction material (though just dry, not wet and dry) so possibly not #3
Damper springs are as per your pic so can rule them out too

Will have to check wheel bearings endfloat & I can't be 100% sure I have not fitted them upside down as I wasn't aware there was a specific way :wall:

Re: Brake pad/disc squeal

User avatar
Post by stuartbyng » Subscribing Member » Sat Jun 30, 2018 8:34 pm
Joined: Fri May 11, 2018 8:50 pm
Posts: 6
Hi again,

Have checked all things mentioned and the squeal is still there :wall:

Any more ideas?

Thanks

Re: Brake pad/disc squeal

User avatar
Post by Phil Bradshaw » Club admin » Sun Jul 01, 2018 1:50 am
Joined: Sun Sep 02, 2012 7:15 pm
Posts: 3579
If everything else is fine then what's left is insecure caliper/s, excessive disc run-out, sticky caliper piston/s, or air in master cylinder preventing proper tandem action. My CF2 has had all of these at one time or another...

Insecure caliper: slight movement can announce itself as a short tweet or squeak as brake first applied; check for rust staining around mounting lugs even if bolts appear to be tight. (Very loose caliper will rattle and knock - another problem entirely!)

Use impact hexagon sockets on caliper bolts: ordinary bi-hexagon sockets can slip and round off the bolt heads. Slacken suspect bolt/s before re-tightening to 165 Nm (120 lbf ft).

Excessive disc run-out: light pedal pressure can induce a series of squeaks before squeal sets in which then may clear as pedal pressure increases. In extreme cases disc run-out can cause sustained squeal and a pulsing or shuddering pedal reaction especially if one or more pistons also sticking.

Checking disc run-out requires a dial test indicator with magnetic base -

Image

First tighten hub bearing nut by hand (40 Nm or 30 lbf ft maximum). Maximum run-out allowed is 0.01mm (0.004 inch).

Slacken and re-adjust hub bearings afterwards.

Sticky caliper piston/s: most likely with age and even if all seem to move ok when fitting pads. The trick is to get them all moving equally which can be done without necessarily having to install a service kit with new pistons.

Special tool is advantageous, Girling type or similar -

Image

Tool basically is a flat bar with a stick welded to it for pushing pistons into their bores; 25-30mm wide flat bar with rounded edges clamped in grips will do if all pistons will move well enough already.

With the front wheels raised from the ground, get someone to heave on the brake pedal then release it so that each wheel can be rotated to assess whether one side drags for longer than the other after the pedal is released which can identify which side is the worse.

Pump the brake pedal until servo assistance ceases then remove one brake pad leaving its partner in place.

Hold your special tool flat against the disc in place of the removed pad then pump the brake pedal to push out the piston to contact the tool.

Temporarily remove your tool and gently clean exposed part of the piston: use spray brake cleaner or cloth moistened with brake fluid. Avoid dislodging dust seal from its recess in the caliper; if a seal is split or torn, or a piston is corroded, then put a service kit on your shopping list.

Smear piston with fresh brake fluid then steadily and evenly retract it using your special tool. Opening the bleed nipple can help: close it while holding the piston fully retracted so that the front brakes don't have to be bled at the end of the job (and don't forget to top up the reservoir after pumping the pedal again!).

Repeat pumping the piston out, gentle cleaning then levering it back in until there is no improvement in how easily the piston can be retracted.

Wash off any excess brake fluid with warm water, dry off then refit pad.

Now do the other 3 pistons so that they're all moving about the same with least effort on your tool.

When putting everything back together double check that all pads are installed the right way up and also that none can bind in a caliper with the pistons fully retracted.

If binding occurs after all corrosion scale has been removed from the caliper then dress pad edges with a file and thinly smear with water-resistant grease.

Air in master cylinder

Usual symptom is soggy/excess pedal travel before full braking achieved and can reduce braking effort in either the front or rear system, usually the front which then can squeal long and loud if any other fault exists.

Apart from squeal this problem can go unnoticed if you've never experienced properly working CF2 brakes and the van still can pass MoT test with heavy enough foot on the pedal.

Assuming that the rest of the system is free of air, open the bleed screw on the master cylinder, fully depress pedal as far as it will go then close nipple before releasing brake pedal; repeat until clean fluid free of air issues from the bleed nipple. Protect paintwork from brake fluid spillage and rinse off any splashes with warm soapy water.

If there was any air in the master cylinder then the pedal action with servo assistance will improve and you may even feel the rear brakes pulling on just before the front brakes depending on how the van is loaded (design feature to prevent front wheel lock-up under heavy braking).

Then cross your fingers. :)
.
  • What is real is not the external form but the idea, the essence of things. Constantin Brâncuși

Re: Brake pad/disc squeal

User avatar
Post by stuartbyng » Subscribing Member » Mon Jul 02, 2018 8:46 pm
Joined: Fri May 11, 2018 8:50 pm
Posts: 6
Great information, again!

I will work my way through the list and see how it goes. Excessive disc run-out may be a likely one though as it definitely starts with a series of squeaks before the loud squeal starts which clears with more pedal pressure.

Thank you

Re: Brake pad/disc squeal

User avatar
Post by stuartbyng » Subscribing Member » Mon Jul 02, 2018 8:55 pm
Joined: Fri May 11, 2018 8:50 pm
Posts: 6
In fact, I think I may need new discs but they seem difficult to source online. Do you recommend anywhere that does them or are they stocked in the Parts Department?

Re: Brake pad/disc squeal

User avatar
Post by Phil Bradshaw » Club admin » Mon Jul 02, 2018 9:26 pm
Joined: Sun Sep 02, 2012 7:15 pm
Posts: 3579
Discs can be hard to find if they can't be skimmed true (minimum thickness 13.2mm).

Solid Transit discs can be modified to fit CF hubs but the hub offset is different so the caliper position has to be altered to suit.
.
  • What is real is not the external form but the idea, the essence of things. Constantin Brâncuși

Re: Brake pad/disc squeal

User avatar
Post by stuartbyng » Subscribing Member » Mon Jul 02, 2018 9:29 pm
Joined: Fri May 11, 2018 8:50 pm
Posts: 6
Thanks for the information, they do seem difficult to get hold of. I will have a better look on the internet at what is available (if there is anything!)

Post Reply

Return to “Brakes”