Brake Pedal Travel - Panhard Rod Length

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Brake Pedal Travel - Panhard Rod Length

Post by Mike Allfrey »

Good Afternoon,

Two questions:

1. Can someone please advise how far the full-hydraulic brake pedal travels until it becomes 'solid'?

2. Again, for full-hydraulic brake system, what is the overall length of the Panhard rod, from shoulder to shoulder?

Any input will be greatly appreciated.

Thanks,

Mike A.
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Re: Brake Pedal Travel - Panhard Rod Length

Post by Keith Clements »

1. Seems variable even though I rebuild MC in the same way and use Silicone fluid on all my three. But I am convinced the main culprit for variance are the seals in the MC. Way to test is to do all adjusters up tight and the MC rod adjuster to no play. Make sure MC returns to start position after each full beans application. Also put foot down slowly. For both hard and slow push the travel should be the same. If you do the above I would expect about 2 cm. Then adjust the MC pull rod for clearance which might add a cm. Then each wheel adjuster for another cm. So max of 4 would be good which is what i have on both Jups. The Jav with servo has 6 cm. But has superb braking

2 measured two panhards between shoulders 73 cm.
Note Jav is different.
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Re: Brake Pedal Travel - Panhard Rod Length

Post by Mike Allfrey »

Many Thanks Keith,

Will measure the actual brake pedal travel tomorrow, but it is much more than you suggest.

We have bled the brake hydraulics using a Toledo compressed air-operated brake bleeding tool a couple of times. It is amazing the number of air bubbles that flow through the clear bleeder tube. The master cylinder has all new seals, plunger and support ring. There is negligible wear at the front housing's pull rod bore. The seal kit and piston came from New Zealand. All wheel cylinders have stainless steel sleeves and new seal cups. The bleed screw threads are plastic coated, but that could be getting tired now, they still have drag on the spanner though.

I have thought about air getting in at the brake fluid joiner hose, the clips are firm and there are no fluid leaks at the supply pipework at all. Will check that aspect further, air can create strange entry points!

I did try using the original method of bleeding the system, but as the pedal was released, the pumped fluid tended to return to the cylinder - seen through the clear tube.

Browsed the Internet on the Toledo tool and found a couple of comments about having to bleed the system maybe up to four times in quick succession to get all air out. That will be tried on Wednesday, as also will your instructions on testing the pedal movement. Will also measure the Panhard rod at the same time for confirmation.

Are master cylinder seal kits available from England? If so, and we are still in trouble, would like to try a set.

All the best,

Mike A.
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Re: Brake Pedal Travel - Panhard Rod Length

Post by Keith Clements »

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Re: Brake Pedal Travel - Panhard Rod Length

Post by Mike Allfrey »

Thanks Keith,

Have measured the pedal travel from home position to brakes applied position, it is four inches. That is with brakes fitted with new linings and properly adjusted.

Looking at the links you provided, it seems that I am not the only one with an excess pedal travel concern. Tomorrow we will lock the brakes using their adjusters and take another measurement in the same manner as today.

We will also try bleeding the system three times in quick succession, to find out if that makes any difference. If it does not, I am wondering about the recuperating seal that came from New Zealand. Interesting to note that there should be a square section rubber ring at the joint between the master cylinder bodies, I have only seen 'O' rings in there. At the Jupiter's master cylinder there is no sign of fluid leakage.

Will update tomorrow,

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Re: Brake Pedal Travel - Panhard Rod Length

Post by Mike Allfrey »

Below is a report on the brake pedal concern.

EXCESSIVE TRAVEL AT BRAKE PEDAL
Background
With the sale of my Jupiter, for transfer to its new owner, it required a Victorian Roadworthy Test (similar to the British M.O.T.) and the test resulted in a not fit for use result. This was primarily because of the brake pedal having too much movement before anything happened in the hydraulics department. This was a bit of a surprise, because back in October last year, I had to carry out work on the rear brakes, due to the right hand brake locking itself extremely firmly to the brake drum.
While the rear brakes were being worked on, it was decided to overhaul the master cylinder. This involved a number of dramas and finding that the car had been, prior to 1962, converted from the original hydro-mechanical system to a full-hydraulic system. Further investigation revealed that the master cylinder body was different in internal dimensions from a standard Jowett specified unit.
The bore in the rear body allowed the plunger to move further back to the extent that the plunger locknut was hard against the front face of the body. Neil assured that there should be about 3 mm gap between the locknut and the housing face. The only way that could be achieved was by inserting about 4 mm worth of spacer washers between the plunger and the bore face in the rear body. Not a good solution, however I was considering having a machined spacer pressed into the bore. This would reduce pedal movement before the drillings in the plunger shell were covered effectively by the recuperating seal. Another difference between the two cylinders was that the one in the Jupiter has UNF threads for the setscrews, the other has BSF threads. Neil kindly sent over a genuine Javelin master cylinder and assembly work continued, there were dramas where the Nylon sleeve tended to pinch the plunger when the three setscrews were tightened home. Over a short period of time, the concern was resolved.
The next step was an air pressure test to establish the exact point when the plunger’s forward travel closed-off the drillings in the plunger shell. The master cylinder was secured in my bench vice at the rear mounting eye bolt, a rubber adaptor was used at the fluid inlet port for low (9 psi) pressure air to be applied. A piece of wool thread was taped to the outlet (pressure) fitting, with the intent that, with the plunger in its home position, the air passing through the drillings to the pressure side and cause the thread to flutter. That it did lustily and, as the plunger moved forward, at about 3 mm of travel the wool thread went limp. That seemed to be satisfactory.
After installing the master cylinder, ensuring the correct clearance at the pull rod clevis, flushing a litre of methylated spirit through the pipework, new brake hoses installed, new wheel cylinder seals which felt firmer during fitting and the system bled of air, the brake pedal travel had not reduced.
Then came the roadworthy test and, as a result, it was decided that the front brakes would get the full treatment. New brake linings and wheel cylinder seals were installed. After further efforts at bleeding the system, the pedal travel was excessive, it was found to be 4-ins. Hence the question posted on Jowett Talk.
Current Activity
Mostly, to date, a Toledo compressed air operated brake bleeding tool has been used.
Today, the activity involved adjusting all brake shoes to firmly lock the drums, the system was bled twice in quick succession, from the furthest brake from the master cylinder through to the closest, some air bubbles were seen during the first bleeding session, and, during the second session the situation appeared to be good.
Pedal travel was measured and found to measure 3½-ins. This was with the brake drums still locked, The brakes were then adjusted to just allow the wheels to rotate freely. Again the pedal travel was 4-ins. – no improvement whatsoever!
Thus, the following questions have to be asked:
1. What have I done wrong?
2. After the pedal has traveled 4-ins., the pedal feels solid, indicating that air is not being compressed, how can that be?
3. Has anyone else undergone such an experience? If so, how has it been resolved?
4. I use Penrite Super DOT 4 brake fluid, is this a suitable fluid for Girling brake systems?
5. What on earth is going on? I am truly at wits end and seriously considering refunding purchasers money so that the car can be donated to a museum, should it be wanted.
I fully understand Keith’s recommendation to use silicone brake fluid, however, the supplier of the seals tells me to stay well clear of it if using his seals. The supplier has a good reputation and supplies to MGs, Austin-Healey, Triumph, Jaguar, Rover and such – therefore they have my trust.
My thoughts have been giving the recuperating seal some consideration, for example, if it were a loose fit on the plunger, surely the pedal would feel spongy.
If air was being drawn into the system at the fitting under the reservoir, or at the joiner hose at the inlet pipe, the pedal again would feel spongey. There are no fluid leaks at the inlet pipe, and there were no air bubbles during the second bleeding session..
There is the possibility that the inlet joiner hose could have de-laminated, but fluid flows freely from the pipe to hose fittings when disconnected. However, it is difficult to see how such a condition can cause excessive pedal travel, and have a solid pedal feel. I can easily understand de-lamination at the joiner hose causing fluid flow restriction during the brake bleeding procedure.
There must be a reason for the excessive pedal travel prior to braking action taking place.
What can it be?
Note: This text will be posted on Jowett Talk, in my thread on this subject, in the hope that someone may have an answer that resolves this problem.

Regards,

Mike A.
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Re: Brake Pedal Travel - Panhard Rod Length

Post by Mike Allfrey »

Today, Friday 28th, we had another diagnostic session. First we blocked the hydraulic flow before the first three-way fitting on the chassis. The brake pedal was solid virtually after pressing in normal manner. The travel was measured to find three-quarters of an inch of travel where it came to a complete stop. It felt really good.

All four brakes were adjusted so that the drums were just scuffing on the new brake linings. Pedal travel was then just under four inches and the brake drums locked at just over three and a half inches.

We suspected fluid leakage at one rear brake, removed the drum and found the wheel cylinders bone dry, the fluid presence at the bottom of the back plate being due to spillage after the repeated bleeding process. It was the same with one of the front brakes.

With the drum removed, the brake pedal was pressed, went straight to the bulkhead as the exposed brake shoes expanded, and returned to home position smoothly when the pedal was released.

All of this begs the question, what is causing the excessive pedal travel? It is a simple hydraulic system, but is extremely baffling.

The master cylinder pull rod movement was recorded on video and it is moving freely. We consider that the master cylinder is operating as it should.

The problem has been narrowed down a little, now for the hard part. It does seem as if modern brake lining material is easily squeezable! Or do modern brake hoses expand?

Are new wheel cylinders available?

All comments and hints welcome - believe me,

Mike A.
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Re: Brake Pedal Travel - Panhard Rod Length

Post by Keith Clements »

Phil has also emailed me so not sure which is the latest.
I thought you had identified the issue down to the front right axle.
Today Mike and I had another crack at the brakes. The video shows the action of the master cylinder as you can see it seems to be fine. Next we clamped off the pipe leading to the MC (see photo). With the clamp on the brake pedal was firm with about ½” – 1” of travel.

Clamping the brake hoses to isolate the problem, it seems the problem is in the front brakes. On the driver’s side, the front brake adjusters lock the drum however the adjusters don’t slacken off enough to allow the drum to spin freely. The passenger side brake adjusters lock up the drum and can be slackened off until the drum just spins freely but they slacken off even further on their own. However I don’t understand how these issues could cause the excessive pedal travel.
I suspect the issue is with the brake cylinder not returning but could be the adjuster, but might be an assembly or spring problem.

I do not think it is an expanding brake pipe as you clamped that. Not a good idea!
Is the shoe sitting properly and central and at 90 deg to backplate? Springs in correct location and are correct?
With drum removed and slowly operating MC do both cylinders come out and return evenly?

Yes new wheel cylinders are available.
Last edited by Keith Clements on Fri Apr 28, 2023 4:15 pm, edited 1 time in total.
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Re: Brake Pedal Travel - Panhard Rod Length

Post by Mike Allfrey »

My thoughts are now with the wheel cylinders and I would be happy to purchase a complete set. Where can they be sourced from?

The wheel cylinders on the Jupiter had been reconditioned with stainless steel sleeves some years ago. They have had new seals installed several times, normal maintenance, but pedal was reasonable, a small amount more travel than my Javelin had. I put that down to the plunger in the master cylinder being allowed to travel further to its home position - the deeper bore in the rear body, meaning more travel before the recuperating seal blocked off the drilled ports in the plunger shell.

We will be removing all four drums and closely examine the movement of each brake shoe, before investigating the internals of the wheel cylinders. My preference is for a new set of wheel cylinders. The brake hoses are new, the metal pipework is in excellent condition.

I agree, I am not at all enthusiastic about clamping brake hoses, but desperation drove us to having a try to isolate the master cylinder, and that proved to be a success - this time.

We will get around to measuring the Panhard rod length while waiting for wheel cylinders.

Cheers,

Mike A.
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Re: Brake Pedal Travel - Panhard Rod Length

Post by Mike Allfrey »

Late last night, while ruminating about the mess that was Q1 at Baku (Formula One) a memory suddenly interrupted my thoughts. Back in the late 1950s, our workshop ran a couple of Standard Ten vans, and one of them gave the mechanic a real headache due to excessive brake pedal travel after a routine overhaul of the brakes. Sadly, I cannot remember what the cause of the problem was - I was not directly involved, but I do remember our foreman getting kind of tense about it!

Anyway, it proves that Jowetts are not the only ones that have such problems. Looking forward to a set of new wheel cylinders - all six of them.

Cheers,

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Re: Brake Pedal Travel - Panhard Rod Length

Post by Mike Allfrey »

Good Evening All,

I think I have resolved the cause of excessive brake pedal travel concern.

We ordered a complete set of new wheel cylinders from Jowett Car Spares, extremely efficient supply service, wonderful five days delivery from DHL and the cylinders look really good.

So, we set to and dismantled the front brakes and after removing the wheel cylinders, removed the pistons and the rubber seals, the first seal popped out and revealed a broken air excluder (H3112) jamming the spring (H3082). Will attach a photo tomorrow, it is cold, wet and dark down here at present! I think this discovery may be the cause of the brake pedal's extra travel. There is a first time for everything.

Thanks Jowett Car Spares, very good value and a great help.

Updates to follow,

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Re: Brake Pedal Travel - Panhard Rod Length

Post by Mike Allfrey »

Hopefully a photo is attached.
A = Wheel cylinder spring with broken piece of air excluder inside coils. From right hand front brake.
B & C = Remains of rest of air excluder.
D = Air excluder from other wheel cylinder, on same side. Partly broken.
E = Spring and air excluder from the left hand side front brake.

This is a 'first for me.

Regards,

Mike A.
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Re: Brake Pedal Travel - Panhard Rod Length

Post by Keith Clements »

Not seen that before. I wonder if piston was temporarily stuck and when it freed itself the impact smashed the bakelite.
Interested to know if any identification on part and the manufacture or age.
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Re: Brake Pedal Travel - Panhard Rod Length

Post by Mike Allfrey »

Hi Keith,

Interesting to know that I am not the only one to have not seen such a failure before.

As far as I am aware the piston was not stuck at any time. The bore was a stainless steel sleeve.

The wheel cylinders were those with the metal dust shroud, not the modern type with rubber boot type dust cap.

Over the years, I have seen the air excluders made from black, grey, white and amber plastic. I have also seen air excluders cast in aluminium and in what looked like zinc die-cast metal. The metal ones were used in combine harvesters and other self-propelled machinery. They looked to be same size and type.

I suspect that age could be a factor for the breakage. Will look at broken pieces with a magnifying glass tomorrow, concentrating on the outer diameter edges.

Have managed to make the funds transfer for the new wheel cylinders, took a bit of work for Sue, but we got there!

Regards,

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Re: Brake Pedal Travel - Panhard Rod Length

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