sized front brake piston

[John Morrison]

David, 1/4 inch is a  quite colossal amount of gap, both sides of both discs?

You do have pads fitted don't you? and how thick are they?

Can you get someone else to push the peddle whilst you see the pistons working?

 

John.

[Z320]

My advice at this point is to give the car to a workshop who knows what he does.

The brakes are to dangerous to work on without knowledge and to give advice without being there.

Edited November 26, 2023 by Z320

[roy53]

I hope that you are bleeding all 4 wheels and not just concentrating the front as it sounds like air.

Roy

[John Morrison]

David you have a PM

John.

[david c]

I may have overestimated the gap between pad and piston but it is certainly considerable, the pedal travels about halfway to the floor before it feels "normal".

I do have pads and shims fitted, the pads themselves have plenty of "meat" on them, I doubt I have driven more than 500 miles since I fitted them,

One way or another I will find a way to watch what actually happens when the pedal is pressed................and released.

I am bleeding the brakes on all 4 wheels.

My feeling is still that the new dust boots are pulling the pistons back,  I think that explains why if pushed in quick succession the second push on the pedal feels normal, if push comes to shove I will unclip one end of the dust covers and see if that changes anything.

I am starting to think that even when I do get this sorted I may well run the car down to the local garage, just for peace of mind.

Thanks as ever for all your help and advise,   David 

[Lebro]

Pushing pedal twice in quick succession will bring it higher up for more than one reason - air in system, too much slack on rear brakes, and you suggestion of "push back"  

Bob

[roy53]

David just remove the dust boots. That will answer your thinking. On the race car they are of no use as they go crispy with the excessive heat so i run without them.

Roy

[Quicksilver]

Is the master cylinder in good condition.?... if the system does not bleed properly, the small cup in the master cylinder is often the culprit....

Marcel

[david c]

Just an update on the brake issues.

It's blinking cold in my "workshop" so I was reluctant to pull the callipers again and unclip the dust boots.

After a suggestion by a member of my local group (East Saxons)

I tried this, I set up a length of 2x1 from  a plywood pad on the front seat to the brake pedal, with just enough pressure to bring the pads into contact with the disk and left it for 24 hours the idea being to teach the dust covers what to do. I didn't hold out much hope of success, stretching the boots in this cold weather was in my mind a bit of a non starter. so before removing the 2x1 I set up a jury rig camera holder and set it to movie mode, all good. but when I removed the prop I looked at the film, I was a little annoyed nothing recorded just a still image.......but when I actually locked at the brakes I could see why, nothing had moved the pads hadn't pulled back from the disks, the movie was working but as nothing moved.............I tried the brake pedal and it just felt normal, no excess travel, just felt right.

I'm not claiming this is the whole answer, but it's interesting, when the weather warms up a bit I'll take the car out for a gentle run up and down the lane and see what's what. In the meantime I have put the 2x1 back in place for a couple of days, can't do any harm.

Thanks all for your help and advise, and thank you Richard C R for your idea.  David

 

[rcreweread]

1 hour ago, david c said:

Just an update on the brake issues.

It's blinking cold in my "workshop" so I was reluctant to pull the callipers again and unclip the dust boots.

After a suggestion by a member of my local group (East Saxons)

I tried this, I set up a length of 2x1 from  a plywood pad on the front seat to the brake pedal, with just enough pressure to bring the pads into contact with the disk and left it for 24 hours the idea being to teach the dust covers what to do. I didn't hold out much hope of success, stretching the boots in this cold weather was in my mind a bit of a non starter. so before removing the 2x1 I set up a jury rig camera holder and set it to movie mode, all good. but when I removed the prop I looked at the film, I was a little annoyed nothing recorded just a still image.......but when I actually locked at the brakes I could see why, nothing had moved the pads hadn't pulled back from the disks, the movie was working but as nothing moved.............I tried the brake pedal and it just felt normal, no excess travel, just felt right.

I'm not claiming this is the whole answer, but it's interesting, when the weather warms up a bit I'll take the car out for a gentle run up and down the lane and see what's what. In the meantime I have put the 2x1 back in place for a couple of days, can't do any harm.

Thanks all for your help and advise, and thank you Richard C R for your idea.  David

 

David - glad the issue appears to have been resolved but in fairness to many others, my suggestion of propping the brake pedal to hold the pressure in the system overnight has been put forward by quite a few previous posters, but it's good to know it appears to have worked in your case

Cheers Rich

[stuart]

16 hours ago, david c said:

Just an update on the brake issues.

It's blinking cold in my "workshop" so I was reluctant to pull the callipers again and unclip the dust boots.

After a suggestion by a member of my local group (East Saxons)

I tried this, I set up a length of 2x1 from  a plywood pad on the front seat to the brake pedal, with just enough pressure to bring the pads into contact with the disk and left it for 24 hours the idea being to teach the dust covers what to do. I didn't hold out much hope of success, stretching the boots in this cold weather was in my mind a bit of a non starter. so before removing the 2x1 I set up a jury rig camera holder and set it to movie mode, all good. but when I removed the prop I looked at the film, I was a little annoyed nothing recorded just a still image.......but when I actually locked at the brakes I could see why, nothing had moved the pads hadn't pulled back from the disks, the movie was working but as nothing moved.............I tried the brake pedal and it just felt normal, no excess travel, just felt right.

I'm not claiming this is the whole answer, but it's interesting, when the weather warms up a bit I'll take the car out for a gentle run up and down the lane and see what's what. In the meantime I have put the 2x1 back in place for a couple of days, can't do any harm.

Thanks all for your help and advise, and thank you Richard C R for your idea.  David

 

What its actually done is allowed the remaining air that was still trapped in the system to purge out. Its an old car dealers trick from the days of drum brakes all round that were notoriously difficult to get all the air out and often lead to spongy brakes. Its a trick Ive recommended umpteen times despite people saying it`ll never work.

Stuart.

[RobG]

What I do not understand is where this air goes as it is a sealed system. It gets purged out to where. Could it find its way back to the master cylinder ?

[Lebro]

Yes, that is exactly where it goes.

Bob

[david c]

All very interesting, I wasn't convinced  that "stretching" the rubber boot, especially in this cold weather could have happened, I was perhaps a little overexcited. Releasing the air in the system does make more sense, and I can't say I wasn't told, by many and often.

The fact the air has now found its way back to the master cylinder mean my problems are over?

Thanks all                David

[Z320]

There is much dangerous phantasy and hope in the thread….