Javelin brakes

[paul wilks]

HELP!!

I have at last started work on my Javelin and have experienced a problem straight away! I hope someone can give me some advice. I must get my car on the road for the rally next year, after all it's only just down the road from me!

I am trying to adjust the front off side brake. Although the hub moves freely initially, once you have applied the brake pedal the 'top' brake shoe refuses to return to the 'off' position. When you extract the hub with the hub puller as the hub is removed there is a sudden 'twang' as the spring pulls the brake back to its 'off' position. The hub is then free again. I have discovered that the right hand brake cylinder (operating the 'bottom' brake shoe) appears to be seized. Would this cause too much pressure being applied to the 'top' brake shoe and would this make it reluctant to free when the brake pedal is released?

It's been suggested that I put a small chamfer on the leading edge of the shoe- which I have done but how small is small? Its also been suggested that if the shoe is 'contaminated' ie by fingers etc. then this might result in the shoe 'grabbing' the hub. Is this likely/possible?

I would appreciate any help as soon as possible.

Thanks

Paul Wilks

[Bryan Walker]

Hi Paul,
I think the problem is the seized brake cylinder, You may find that it is moving a bit under hydraulic pressure to in-gauge the shoe but not returning.
When over hauling the cylinder, if the piston has lost its white metal coating - replace it as it will cause the same problem again later on.

Bryan.

( Had similar problem with left rear where one piston was not free to return)

[pat lockyer]

First are we talking about the early hydro mechanical single front wheel cylinder on each front wheel or the later twin cylinder set up.
I assume the brake adjuster has first been completly let off before the use of the puller?
One adjuster on the early type and two on the later.

[paul wilks]

Thanks for this so far, Pat and Bryan. It is the fully hydraulic system. Looks like I will have to order a replacement brake cylinder for the 'bottom' shoe. As I said it appears that the 'top' shoe is working correctly but perhaps doing all the work(?)

I will keep you updated about progress.

Thanks for your help

Paul

[Tony Fearn]

Hi Paul. There are proprietary brake disc and shoe cleaning aerosols available for about a quid a cannister which should help remove "sticky finger exudates" from the braking surfaces, although from what others have said it seems to be a little more involved. Nevertheless, giving the drum and the shoes a squirt and wipe down won't do them any harm. Good to see you after all these years at Bingley. Regards, Tony.

[Forumadmin]

Please have a look at the section http://jowett.org/jowettnet/dt/tech/bra ... brakes.htm
Of course, clean everything after dismantling the cylinders, examine for scouring, replace or hone out with cylinder honer; if the rubbers are of indeterminate age, renew them. Get spare cylinders anyway and put in your spares kit, if you do not use the car regularly clean all the old fluid out and replace with silicone. This si a long job but brakes are very important. Also dismantle and clean out the master cylinder and reservoir. There is usually a load of crap in both that will scour any new seals you put in.

[pat lockyer]

If you go racing on silicone do crack the bleeders and pump out some fluid before each race.
As we know silicone is not hygroscopic so any moister will settle at the lowest point the wheel cylinders in this case and boil with excess heat loseing the precise pedal feel.Tut Tut.
One advantage with silicone no corrosion within the cylinders but sticking cylinders is most common.

However the proven way is the use of DOT 3/4 and change every two years.
fluid for racing is another ball game!

regarding the brake notes from admin i note that the somtimes common cause of brakes binding has not been mentioned unless i missed it speed reading! this is the collapse of the internals of the brake hoses, beware.

[Keith Clements]

Certainly all hoses must be firm and make sure they do not rub anywhere on full lock or full bump.

[pat lockyer]

And most important to make sure they are long enough on full rebound!

[David Morris]

Hi Paul,

I am sure all the advice you have received is spot on and that a new wheel cylinder (s) will sort out the problem.

However, the only comment I would like to add is that you mention that this problem occurs when you apply pressure to the foot pedal. Now this could well be the cylinder jamming but, as Pat mentions, it could just as easily be the rubber hose to the wheel from the body frame.

I have had these fail internally in the past, with just the same symptoms! You get bits of rubber apparently peeling off the bores and causing internal blockages. A bit like a non-return valve.

To source new hoses, and to avoid any problems with 'new old stock' hoses, I can recommend our local racing circiut suppliers, Merlin Motorsport at Castle Combe Race Circuit. ( phone no. 01249-782101 ) They will supply new stainless steel braided hoses, to your length and with all the correct ends, at a cost which is very comparable to conventional rubber ones. They make them up on site, so you can walk away with new ones in your hand! I purchased a set for our Javelin a couple of years ago and they have worked fine. The MOT inspector likes them too!

Hope this is useful,

David

[Chris Cole]

I too experienced brakes stuck on on my wife's Peugeot 205. The inside of the hose had de-laminated (or whatever) and bits intermittently stuck in the hose and made a very good one way valve. Only cure - new hoses.

[paul wilks]

Thanks for all the advice to date. I have received today a new cylinder from Bill Lock. I will let you know how I get on when I have fitted it. I hope and pray I don't have to replace all the hoses!

Thanks for your help

Paul

[PAUL BEAUMONT]

One more thought for you Paul. Can you be sure of the fluid that is currently floating about in the brake system. I too have experienced the de-laminating hose problem, but one that really baffled me for a while, a few years back on a Morris Minor was fluid that some idiot had contaminated with some sort of mineral oil. This caused seals around the system to swell and exactly the sort of thing that you describe happened. Eventually the master cylinder sucumbed (and these thing are swines to extract from their bizarre location)
Before you fit the new cylinder I recommend fully flushing with new fluid. As you bleed each brake the fluid should squirt out freely and rapidly. Anything but could well indicate flexi prooblems, but should help you pinpoint which one!

[paul wilks]

Thanks everyone. I should have said that I flushed out the system only last year (or the year before) using new Silicone fluid (Automec) as recommended and supplied by Bill Lock. The brake hoses are relatively new. I have now fitted the new cylinder and the brakes appear to be working okay and the front offside brakes are actually releasing when the pedal is released. So it appears the non functioning cylinder was the culprit after all and the poor remaining cylinder was doing all the work and refusing to release. You (I!) learn something every day about Jowetts.

All I have to do now is bleed the system and let's all hope and pray that everything in the braking system works then. I can then concentrate on getting her to start and getting her through an MOT.

It would be good to drive her again after 30years off the road!

Doubtless I will be contacting you good helpful people as I encounter other problems in getting my Javelin back on the road!

Thanks. And I'll let you know (and bore you rigid) about my progress.

Paul

[pat lockyer]

Just one added note on the above silicone sinario.
You can change to silicone from dot 3/4 without changing seals hoses etc but you cannot change back to dot 3/4 without the complete replacement of all rubbers within the system.
In my experience, not good to go down the silicone route in the first place!