Soft pedal but no air in the brake lines?

[Patrick Taylor]

OK, so the front brake replacement is done -has been for a couple of weeks, but the results aren't perfect. There is no air when I bleed the brakes (using a Gunson Easibleed, i.e. pressurised bleeding), but the pedal travels further than expected when I apply them. They do stop the car, though. If I pump the brakes, the pedal firms up and there is less travel on the pedal.

So my question is this: is this a case of needing to bed the brakes in (new calipers pads and discs have been fitted), or do I go back to bleeding the offside rear and work forwards again (I have done so several times in the past fortnight), even though there is no sign of air? I am not keen on using the car on the Queen's Highway in its current state, although if it is just a case of bedding the brakes in, where I can expect to see an improvement, I would do so. I think I should have a solid pedal right from the off, but is this not the case?

[NonMember]

Just now, Patrick Taylor said:

new calipers

There have been several reports that new calipers are not machined quite right, so the piston can't "slide through" the seal as it's supposed to, and therefore pulls back away from the disc. This gives the long pedal that you're experiencing. Apparently sometimes improves if you wedge the pedal hard down overnight.

[johny]

Also Ive found in older vehicles the pads sometimes dont sit exactly parallel with the disc so to start with the pad only contacts in a reduced area giving a spongy pedal. After some miles theres complete contact so the braking will be better and the pedal more solid. You could check the pads to see if this is the case...

[Chris A]

I have/had this when I replaced mine last year. Not spongy but just a fair bit more travel than before the replacement.

I have done the wedge the pedal thing a couple of times, not an immediate improvement. However the last few times I have taken the car out the pedal travel is much reduced and 'solid' feel to it. Maybe they just take a long bedding in period. 

[Patrick Taylor]

5 minutes ago, NonMember said:

There have been several reports that new calipers are not machined quite right, so the piston can't "slide through" the seal as it's supposed to, and therefore pulls back away from the disc. This gives the long pedal that you're experiencing. Apparently sometimes improves if you wedge the pedal hard down overnight.

 

3 minutes ago, Chris A said:

I have/had this when I replaced mine last year. Not spongy but just a fair bit more travel than before the replacement.

I have done the wedge the pedal thing a couple of times, not an immediate improvement. However the last few times I have taken the car out the pedal travel is much reduced and 'solid' feel to it. Maybe they just take a long bedding in period. 

Perhaps I need to go for a run while the roads are quiet. Trouble is, my last outing in the car was total, foot-to-the-floor brake failure, with the handbrake applied to avoid rear-ending the car in front , so I've lost a bit of confidence in her...

[Mark B]

In my experience, if the pedal firms up when you pump it, it would usually indicate there is still air in the system. I would bleed them the old fashion way, with the help of an assistant. I use a bleed pipe in a jar of fluid, but lock off the bleed nipple before the assistant lifts off of the floor for the up stroke. I always thought there is a chance air could be sucked in around the thread of the nipple.

[68vitesse]

21 minutes ago, Mark B said:

I always thought there is a chance air could be sucked in around the thread of the nipple.

Bit of grease around the threads should seal them, have used this method when solo brake bleeding. Also tend to push pedal down fast and let up slowly.

Regards

Paul

[Chris A]

1 hour ago, Patrick Taylor said:

Trouble is, my last outing in the car was total, foot-to-the-floor brake failure,

I would also say air in the system. The 'new caliper syndrome' gives firm brakes but longer travel, it seems the seals hold the piston to tight and pull it back further from the disc. There was an article about it in the club magazine a while back :

[Patrick Taylor]

1 hour ago, Chris A said:

I would also say air in the system. The 'new caliper syndrome' gives firm brakes but longer travel, it seems the seals hold the piston to tight and pull it back further from the disc. There was an article about it in the club magazine a while back

An interesting read. I may try a short run to see if things improve, but if the suggested hack is as effective as it sounds it must be worth a try.

[PeteH]

Because I had a "Brown Trouser" moment some years ago with a 9t Motor-home. which required a full fluid change. Something I do now every 2 years or even less if stood. I have a Air driven Vacuum Brake bleed kit, which allows me to solo bleed.  https://www.amazon.co.uk/Sealey-VS020-Pneumatic-Bleeder-Multicoloured/dp/B008632ERA/ref=sr_1_4?adgrpid=114098198150&gclid=CjwKCAiAwKyNBhBfEiwA_mrUMqqZtKhdX9RK2Vn8TZzJHxnZ5iINHFXyZpq_XxFv9QAhRl8oh6_4YRoCLxoQAvD_BwE&hvadid=469071168464&hvdev=c&hvlocphy=1006816&hvnetw=g&hvqmt=e&hvrand=7398883923580443282&hvtargid=kwd-416104248407&hydadcr=1132_1867099&keywords=sealey+vacuum+brake+bleeder&qid=1638626813&sr=8-4

Don`t know if that is of any assistance?

Pete

 

[Pete Lewis]

travel can be incorrectly set hand brake cables holding the wheel cyls open 

always bleed use a catch jar up high above the wheels 

and new pads take some bedding in 

attached is the mintex plan , if you make them smoke youve gone a bit to far

mintex bedding.pdf

[Patrick Taylor]

27 minutes ago, PeteH said:

Because I had a "Brown Trouser" moment some years ago with a 9t Motor-home. which required a full fluid change. Something I do now every 2 years or even less if stood. I have a Air driven Vacuum Brake bleed kit, which allows me to solo bleed.  https://www.amazon.co.uk/Sealey-VS020-Pneumatic-Bleeder-Multicoloured/dp/B008632ERA/ref=sr_1_4?adgrpid=114098198150&gclid=CjwKCAiAwKyNBhBfEiwA_mrUMqqZtKhdX9RK2Vn8TZzJHxnZ5iINHFXyZpq_XxFv9QAhRl8oh6_4YRoCLxoQAvD_BwE&hvadid=469071168464&hvdev=c&hvlocphy=1006816&hvnetw=g&hvqmt=e&hvrand=7398883923580443282&hvtargid=kwd-416104248407&hydadcr=1132_1867099&keywords=sealey+vacuum+brake+bleeder&qid=1638626813&sr=8-4

Don`t know if that is of any assistance?

Pete

 

Not for  my garage: it requires an air line, which I don't have. The Gunson system uses a tyre at 20 psi.

[Pete Lewis]

most will use a right foot   down quick, nip nipple,  back slower ,  open nipple  ,  down quick 

top up and keep jam jar up high  

easy to make a bleed pipe valve  

plug end of tube    use sharp blade make a slit in the tube about 3/4" long  this acts as a valve allows fluid out 

and closes on returns 

 

simpluze 

Pete

[Colin Lindsay]

52 minutes ago, PeteH said:

Don`t know if that is of any assistance?

Pete

I have one gathering dust somewhere; never could get it to work satisfactorily. Probably just me...

[dougbgt6]

2 minutes ago, Colin Lindsay said:

I have one gathering dust somewhere; never could get it to work satisfactorily. Probably just me..

You mean the assistant? 

Doug

[PeteH]

1 hour ago, Colin Lindsay said:

I have one gathering dust somewhere; never could get it to work satisfactorily. Probably just me...

Needs 90psi of air. But mine works well enough to have replaced the fluid in what (was basically) A Fire Truck chassis. 

Pete.

[Patrick Taylor]

Just returned from a run: the brakes work, but are better with a preliminary shove on the pedal. The travel seems less when the handbrake is on; is that because I've just braked, or could it point to the rear brakes being out of adjustment?

[Colin Lindsay]

2 hours ago, dougbgt6 said:

You mean the assistant? 

Doug

The point of those, and I must have tried half a dozen over the years, is to remove the need for an assistant. "I've got this whining noise from the brakes.... shouldn't have asked her to help, then...."

[PeteH]

1 hour ago, Patrick Taylor said:

Just returned from a run: the brakes work, but are better with a preliminary shove on the pedal. The travel seems less when the handbrake is on; is that because I've just braked, or could it point to the rear brakes being out of adjustment?

Try backing off the handbrake, adjust the rears. Then the hand brake. And see if it improves?

In my view you never adjust the hand brake without ensuring the rears are spot on?.

Pete

[NonMember]

56 minutes ago, PeteH said:

never adjust the hand brake without ensuring the rears are spot on

Yes, no point trying to set the handbrake if the shoes are out of adjustment. Also, you need the rear axles under road load, not dangling against the chassis, when adjusting the cable.

[Andrew]

This is how you solve your issue.  I had exactly the same issue when I replaced both my front callipers on my 13/60.  Do it one side at a time. Remove both pads out of the calliper give the pedal a couple of pumps to get the pistons out of their normal position, and make the piston seal movement. Push both pistons back in replace pads and do the same on the other side.  I guarantee that will fix the problem.  The piston seals are dragging the piston back into the calliper and not allowing any movement 

 

Andrew

[Pete Lewis]

20 hours ago, Pete Lewis said:

travel can be incorrectly set hand brake cables holding the wheel cyls open

couple of clues  

the handbrake lever pivot pins can wear a groove in the back plate stops the cyl from sliding properly

always raise the axle to a near running height  and  not hanging (as  Rob said ) disconnect the handbrake cable ( just one end) and fully lock up hard the adjusters on both  rear  brakes

now reconnect the cable adjust the fork end and clevis to a nice neat fit  no tension /no slack    then de adjust the adjuster some 4 clicks or just enough to free the wheel 

Pete

 

 

[Nick Jones]

On 04/12/2021 at 10:59, NonMember said:

There have been several reports that new calipers are not machined quite right, so the piston can't "slide through" the seal as it's supposed to, and therefore pulls back away from the disc. This gives the long pedal that you're experiencing. Apparently sometimes improves if you wedge the pedal hard down overnight.

If new (repro) calipers, it will be this. 
 

You can prove it by removing the pads one at a time, carefully pumping the piston out a little, then levering it back in just enough to squeeze the pad back in. Repeat for the other three. If you now have a decent pedal, the issue is proven. This will remain for a few miles until the pads wear down as they’ll “adjust” back to where you are now.

The best solution IMO is to remove the repro tat and return to supplier for full refund as unfit for purpose. Or you could waste hours of your life (as I did) repeating the above at intervals in the hope that the seals will “get the idea”. They won’t. You could try fitting alternative caliper seals in the hope that’ll resolve the issue. I tried 3 different versions including some used OE ones from an old caliper.  That didn’t work either. IMO the shape of the seal groove is wrong.  Certainly it’s different from OE.

I’ve posted about this on here before

https://forum.tssc.org.uk/topic/3884-suspect-repro-girling-type-16-callipers/#comment-42468

Nick

[johny]

Has this repro problem been found with calipers other than type 16? I believe Patricks Bond might not have these....

[Patrick Taylor]

@johny is right: the Bond has Type 14s. Although I get the impression the problem may be the same/similar...