Long Brake Pedal Stroke

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S

swifty man

Member
Posts
17
Location
durham
Hi All
Recently did some major work on my defender 90 brakes which has drums on the rear. Fitted new front discs and pads, stripped front calipers and fitted new pistons and seals (split them in half first), replaced both front flexi pipes with standard rubber hoses and replaced front pipes with copper.

The problem is the pedal has a long stoke before the brakes start to work this was after i eezi bleed the whole system three times. I then replaced the master cylinder doing a bench bleed before fitting to the landy, eezi bled the whole system and also had somebody push the pedal while the eezi bleed was connected but still the same.
The front wheel will lock up when the brakes are stamped on but the pedal travel is still greater than before i started to overhaul the brakes.

Have i missed some thing or is the way to adjust the pedal travel.
 
Check the rear adjusters first, make sure the shoes are just catching, then back off a tad. They will need re adjusting a short while after fitting new shoes..
 
if adjusting rear shoes doesnt help, pull master cylinder away enough to adust the servo push rod (screw out ie anticlockwse) you need someone to press brake pedal down and some decent long nose pliers to hold rod it can come adrift quite easily, you may need to adjust a few times trail and error to get it correct if adjusted too far pedal will have no free play and brakes will pull themselves on sometimes after a few miles
 
Still has the original rear drum shoes fitted, ive not had the drums off so the adjustment is still the same it was before i overhauled the front brakes/lines.
 
Ive given the problem some thought and think i need to buy three pipe clamps to see if its a front or rear problem then if this draws a blank ill pressure bleed again.
 
Fault will be slack wheel bearings allowing the disc to knock the pads back into the calliper, if its better on the second press of the pedal its almost certainly bearing adjustment.
Old guy told me years ago, if something is different after you have worked on it, you have fcuked up somewhere even if you didnt touch whatever has gone wrong, the old sod has been right many many times.
 
freelance said:
^^^^know that feeling!!
Click to expand...

He told me that knocking on for 25 odd years ago and every time something goes tits up I think of old Ronny, when he was concentrating his tongue would slightly hang out like a senile old cat:D:D
 
The wheel bearings have been replaced at the same time the brake overhaul, .00015 th end float, used a dial gauge to set the end float. Ive rechecked this and its still the same. Before the brakes were overhauled the off side bearing had about .080th end float, reason why both bearings have been changed.
The brake pedal did not have as much travel then as it has now.

Also jacked the rear up today and checked the drum brake adjusters but all ok there too.
 
swifty man said:
The wheel bearings have been replaced at the same time the brake overhaul, .00015 th end float, used a dial gauge to set the end float. Ive rechecked this and its still the same. Before the brakes were overhauled the off side bearing had about .080th end float, reason why both bearings have been changed.
The brake pedal did not have as much travel then as it has now.

Also jacked the rear up today and checked the drum brake adjusters but all ok there too.
Click to expand...
have you looked at post 3
 
Did a static check for the rod to piston free play, engine off and push brake pedal with hand until resistance is felt (rod makes contact with mc piston), free play 8/10mm which is within spec.
 
swifty man said:
Did a static check for the rod to piston free play, engine off and push brake pedal with hand until resistance is felt (rod makes contact with mc piston), free play 8/10mm which is within spec.
Click to expand...

You have air in more than likely the rear tandem cylinder or rear system would be my guess, if front brakes work to some extent but the rears don't. That or there is an internal seal fail in the MC or it is internally assembled incorrectly.
 
Would the previously rebuilt sticking calipers cause less brake travel.

And now they are rebuilt and the pistons moving freely you have more travel?

Although it does sound like air to me. It's surprising how much a very small amount of air can cause the pedal travel to increase. (Been there)
 
ONE LIFE LIVE IT. D90 said:
Would the previously rebuilt sticking calipers cause less brake travel.

And now they are rebuilt and the pistons moving freely you have more travel?

Although it does sound like air to me. It's surprising how much a very small amount of air can cause the pedal travel to increase. (Been there)
Click to expand...

To some degree but not to a great degree. Caliper pistons only move thousandth of an inch to contact or withdraw from the discs. So whilst there maybe a slight amount of extra travel or the brake pedal will feel freer with freed off calipers to some extent it should not travel grossly further as you describe. The first part of the tandem cylinder feeds the front brakes the second part the rears. The idea being that if one circuit fails the other is still active. However if one part of the cylinder or system has air in it, the air is compressed before the airless circuit can work. Start by bleeding the cylinder furthest from the master cylinder and working back towards it. Best way to drive out stubborn air is to fit your bleed tube as normal but get an assistant to pump the pedal up and hold pressure on it. Then release nipple with pedal held down tighten nipple and slowly let pedal up then repeat until all air is blown out. Repeat as needed for both circuits on all wheels.
 
wammers said:
To some degree but not to a great degree. Caliper pistons only move thousandth of an inch to contact or withdraw from the discs. So whilst there maybe a slight amount of extra travel or the brake pedal will feel freer with freed off calipers to some extent it should not travel grossly further as you describe. The first part of the tandem cylinder feeds the front brakes the second part the rears. The idea being that if one circuit fails the other is still active. However if one part of the cylinder or system has air in it, the air is compressed before the airless circuit can work. Start by bleeding the cylinder furthest from the master cylinder and working back towards it. Best way to drive out stubborn air is to fit your bleed tube as normal but get an assistant to pump the pedal up and hold pressure on it. Then release nipple with pedal held down tighten nipple and slowly let pedal up then repeat until all air is blown out. Repeat as needed for both circuits on all wheels.
Click to expand...

That's very interesting. So there are two pistons in the brake master cylinder, the one closest to the servo is for the rear brakes, furthest away from servo is for the front brakes?
 
ONE LIFE LIVE IT. D90 said:
That's very interesting. So there are two pistons in the brake master cylinder, the one closest to the servo is for the rear brakes, furthest away from servo is for the front brakes?
Click to expand...

Yes, basically if the rear brakes have air in the circuit then the pedal will go down until that air and the first chamber return spring is compressed before the front brakes receive any push from the servo. So you will get a longer pedal travel. As you would if the rear brake circuit had failed.
 
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