9 replies to this topic

[chuee]

Hello folk, I'm wondering what you may have to say about irritating brake pad drag on front disks.

 

This is my story: the brakes worked, but pads were worn and  pistons rusty. No noise when driving.

 

I replaced the pistons with stainless, new seals and, new disks and pads. I did not replace the spring clips.

 

After that replacement, There was drag noise form the pads which increased with speed.  Not nice at 50 mph.  I  supposed would soon settle in . It didn't. 

 

 

Checking the pads I found they were not all releasing the same, on both sides. 

Tried working the pistons in and out a good number of times to 'loosen them up' That helped with one pad, as I could tell from moving the pad at rest, to see what 'release play' was there. But overall after a couple of hundred miles or so, they would not settle down.

 

I re-installed the pistons specifically with lockheed seals. Although definitely quieter, especially at speed below 30 mph, Same problem overall persists and is unacceptable.  I've driven 250 miles on motorway and town.  Some pistons are more released than others.

 

I wondered if it may be due to the pistons.. I think I bought them from  Moss Motors. Probably made in China.

I've ordered new pad spring retainers, but doubt that is cause.

 

Comments offering insight appreciated.

Edited by chuee, 27 October 2020 - 10:26 PM.

[GraemeC]

Are the pads free in the calipers - with the pistons wound right back can the pads rattle slightly?

Presumably there was no signs of the seals deforming or being pinched when you replaced them - were the grooves fully cleaned out?

 

Pads/pistons not returning is normally a sign the seal lips are dry. But if you've worked them in and out a few times that shouldn't be an issue.

[chuee]

Thanks GraemeC: yes the pads are free and can rattle with pistons pushed in. The seals were good, and fitted with care - twice. Grooves meticulously cleaned.

 

Your observation, that pistons not returning completely, being a sign the seal lips are dry is useful; I had wondered. I guess you mean it applies to both inner and outer seals. 

 

Which makes me turn my attention to the outer seals particularly. I wondered if a little easing with silicon spray on the outer seal might be useful?

 

I had not lubed the outer seals with anything, except a very little brake  fluid.  Also, as you may have found from their fitting, the outer seals are slightly harder to fit square, due to their casing and location,  I reckon - much more likely to be slightly 'off'. I could give the outer seals some special attention.

 

John

[chuee]

 I've lubed the outer piston seals with silicon grease, without removing the pistons... but by applying to the pistons them a bit. Also replaced with new, the anti-rattle springs.

 

Only taken it for a short run, still noise; I'll run her a bit to see...........and if no real difference I'll remove the calipers and outer seals, replace with red rubber grease on new outer seals.

Edited by chuee, 29 October 2020 - 10:51 PM.

[GraemeC]

Are you using rubber hoses? How old are they?

 

They could be starting to break down internally and just starting to act as one way valves - enough to resist the pads moving back, but not enough when they're forced back

[chuee]

Are you using rubber hoses? How old are they?

 

I fitted new hoses at the same time as fitting new pistons. 

 

I think red rubber grease is more lubricating than silicon, I reckon.

Edited by chuee, 01 November 2020 - 01:56 PM.

[chuee]

Update:  Overall I'm unhappy with the seals, and my being able to trust them as good. They differ according to supplier!

 

I checked the Rover Service manual, and confirmed  that it does not specify using grease at all, but just brake fluid to lubricate, which is what I did at first.

Now I've greased the piston and the outer seals. It make no sense to me to use grease on the inner piston especially, and never have in the past.

 

I checked the outer seals carefully, and see that of all seals supplied to me - original Lockheed and not, they all are different, in material composition (flexibility, hardness, etc) , and what's more they differ in size  of inner diameter and thickness quite markedly, although all fit over the piston - the more flexible ones being the smaller ones. 

 

The inner seals supplied  are different in thickness and composition material too. 

At the moment I'm suffering from two pistons  and inadequate retraction, one on wheel, both on the inner pistons. These both have lockheed inner seals, but not sure what outer seals, by now.

 

For the next re-build I want a reliable supplier. 

[Spider]

For what ever it's worth, I've been using Rubber Grease on these parts instead of Brake Fluid as an assembly lube for longer than I remember and I can't say I've had an issue from that.

 

I'm just wondering in fact if this is a Master Cylinder and / or Pedal and / or Servo (if you have one) issue ?

 

If the Master Cylinder doesn't return all the way back, the Ports venting back to the Reservoir will still be covered and also will maintain some pressure (and displacement) in the Hydraulic Circuit(s).

 

One quick way of determining of this in fact is the issue is to go for a drive until the problem is quite apparent, then stop and as quickly as possible, crack open one of the front bleed nipples, you'll ant to watch it closely as you do. If it gives a small spurt of fluid before reducing to a low dribble, then that would indicate residual pressure in the system. It won't be much of a spurt. If it dribbles right away, then that would show there's no residual pressure.

 

See how you go with that first.

[no66]

Some combos of polished piston and seals are some times too "slidey" 

The square section inner seal actually grips the piston and twists when applying the brakes. When you release pressure the seal pulls the piston back a fraction stopping drag. 

 

[chuee]

 

I'm just wondering in fact if this is a Master Cylinder and / or Pedal and / or Servo (if you have one) issue ?

 

 

See how you go with that first.

Appreciated. I was wondering loosely about this issue... I'll check it as you suggest.