Theses brakes are driving me mad!

[v8wgm]

I have an MOT on Friday and my brakes are duff! With full effort on the pedal I cannot get the front wheels to lock up.

The system (all standard setup): Master cylinder (unknown)
New bits: brake lines, flexible hoses, caliper pistons & seals, discs, wheel cylinders & linings.

The pedal is going down too low for me. I have tried to test the master cylinder by holding a lot of pressure on it for a couple of minutes & the pedal does not sink. The servo is working OK. I have pressure bled the system three times now & there is no fluid loss. Everything is moving as it should OK. Nothing sticky.

Could it be the master cylinder? I would have thought if it holds pressure for such a long time it was OK.

Cheap, nasty pads maybe?

Please help!

Gavin

[Andrew S]

Hi Gavin

The natural check is fluid loss or level and servo, but brakes can be a adjustment too. For example, I would look at the rear shoe adjustment. Are the adjusters working? If not and they are not adjusted, then there will be a lot of brake travel. You mention that you cannot get the front brakes to lock up, well thinking about, its not such a bad thing, especially on a wet road. I have driven quite a few Stags in my time and some of them have had a brake biting level, very low down on the pedal, as if the front pads needed replacing. When I checked, they were as good as new.

I would look at rear brake adjustment first by remove the drum and see if the adjusters are working to the point that I knew the drums were just kissing the drum as I turned the wheel.

I am sure others with have other suggestions on here but if the servo is working and brake pedal doesn't drop,then rule out hydraulics.

[v8wgm]

Thanks for that Andrew

I forgot to mention that I had manually adjusted the rear shoes so they are just kissing & no more. At least I have a handbrake now.

I just took it out and drove with the brakes on until they faded away to try & bed the pads in a bit. On my return I noticed the fluid level has dropped a bit (I think, mind you I am losing it today!) but I need to check I'm not losing it throught the bleed nipples.

I'll check those, wait 'til it cools & then try it again.

I've now marked the level, so if it does drop it looks like the m/cylinder.

Gavin

[v8wgm]

Took it out again, driving with heavy braking.

No fluid loss from the resevoir.

Now totally stumped. I pressure bled from the farthest blled point to the nearest, then on the second attempt the reverse of this. Third time back to the normal routine.

I have had some stubborn airlocks on other cars but never a problem with a Stag.

Are there some nasty pads on the market?

[V Mad]

If you fitted new pads & discs they will not be up to full strength until bedded in. Also the rear brakes will need to bed in too.

[v8wgm]

Thanks Chris,

I do think they are improving ever so slightly but I've never felt any brakes so bad. I just don't like the fact that with full on brakes the fronts don't lock. The rears do.

I went into town for more brake fluid in my four drum series 3 land rover and nearly plastered myself against the windscreen using the same pedal pressure!

In the brake master cylinder, is it possible for the fluid to bypass the seals & return to the resevoir? In saying that the pedal does not feel to sing with constant pressure.

[flying farmer]

If your back brakes are locking before the fronts I would suspect a pad issue. There are a lot of different pad compounds on the market for pads that will physically fit the caliper, but belong on a different specification vehicle. Also heating some pads to the point of fading seems to destroy the material. I became an expert on brake fade when I ran a Toledo with a tuned 3.9 Rover V8. One problem I found, was that when a pad was heated to the point of fading, as it cooled the centre sank, resulting in the only contact between the pad and the disc being about the outer 1/8th of an inch of the pad. This then had to wear down flat before full braking was restored. By this time they had usually been faded out again. Some pads never came back again, and ended up looking like bakerlite. I could fade out full race front and rear brakes in less than 2 miles if I was driving vigorously, which is why it was used for drag racing, not circuit racing!
Neil

[pcoleman]

it's a long shot but it may be the front flex hoses are collapsing internally if they are a good age,I have read this in one of the triumph mags ( TSSC ) dont tell anyone and it caused a very similar problem to what you describe.the issue being resolved by fitting new stainless braided hoses.

peter

[keeny]

How were the brakes before you replaced the front pads

[v8wgm]

The pads were in the car when I got it but are pretty recent. I didn't think the brakes were bad but then I wasn't trying emergency stop tests for the MOT.

The hoses are all new & I've checked that they aren't ballooning & that the fluid flows freely.

I think Neil is right that it could be a pad issue. This morning I disconnected the pipes from the master cylinder and fitted bleed nipples & bled. The pedal is rock solid with & without servo assistance. So either it's pads or there is one mother of a bubble that I can't shift. I'll try & get a set of pads today & re-bleed the entire system.

Gavin

[Sheepdip]

Have you centralised the shuttle valve? Having literally just worked on my brakes know how position sensitive this is! BTW I haven't got the switch screwed in, use a nail to detect centre, but looking at the switch last night its quite a strong spring, is this to hold the plunger centrally against slight movement due to brake movement?
Paul

[jbuckl]

How old are the hoses?

(Have come across collapsed hoses on a stag last year but symptom was sticking on brakes)

New master cylinders are cheaper now than 20 years ago. If you know where I'm coming from?

Is the servo really working?

[v8wgm]

Thanks for the replies guys.

Each component now inspected and I'm 100% happy with every one.

System pressure bled twice. New Apec pads fitted and starting to bed in.

The result is a slight improvement. I can now lock the front wheels in the wet. It hasn't been dry to test them

This is the standard system on the donor Stag I bought to convert my own to TV8 so this one now has the Ford lump. I am now wondering am I just not used to the standard brakes with my own having the Monarch 4 wheel brake conversion or is it the fact that someone has fitted 185/90 R14 tyres to it & the extra diameter is sucking the life out of the brakes. They are huge! I have noticed that the larger tyre size has dulled the performance from the Ford somewhat.

[keeny]

Its worth a thought most of us use the stags as weekend cars not daily drivers ,hence we switch between modern daily drivers and the classic stag,the lack of use and the change in brakeing performance over the years sometimes creats a problem that did not exist nearly 40 years ago

If poss try using the car more to bed pads in properly or change pads for EBC type greenstuff good luck


keeny

[Sheepdip]

I find the brakes on the Stag are fine, a stamp will lock front brakes (at low speed), a pull on the handbrake will lock rear brakes. I've had more trouble with the shuttle valve tho, my youngster was helping me re-center it only yesterday after I overhauled the callipers. Do the rear brakes lock before front? Try reversing and braking, is it better than forwards? If so the valve is not centralised.