Javelin brakes

[Forumadmin]

clearly the debate on Silicone versus Glycol will go on. From personal experience, in the first 20 years of owning Jowetts I had problems with wheel cylinders every year. I have at least 20 cylinders as proof. Now they may not all have been caused by fluid; but at least half were. Since switching to Silicone in 1988 I have NEVER changed a cylinder or had to do any maintenance apart from renewing the flexible tubes. All my racing and rallying was performed on Silicone, including some extremely hard driving in the Atlas mountains when many other cars suffered from boiling fluid. Dot4 fluid is to be recommended for high boiling point in disks; but I doubt it is necessary with drums. The amount of water vapour inside the reservoir is small, especially if you keep it topped up. The amount that would condense would also be small and it would probably settle in the bottom of the reservoir; only with an extreme amount of bumping would it descend into the system as the entry pipe is higher than the base of the reservoir. With glycol you must change the fluid completely every 3 years because it agressively absorbs water all the time, not just when condensing conditions occur. It distributes the water all through the system. Worse, a coating of the fluid on the cylinder walls also absorbs the water, hence the rusting and oxidisation of the aluminium. This does not happen with Silicone.

[Keith Andrews]

Some basic and important rules for brake fluids
1/Dont mix different types
2/If changing from 1 type to another...make sure u have COMPLETLY flushed the system.
3/When bleeding, start at the wheel fartherest from the master cylinder
4/NEVER add fluid that has been bleed out, back into the system
5/NEVER leave the lid off the bottle or master cylinder
6/NEVER use a bottle that has been opened and sat on the shelf for some time.
7/If u have fixed a leak...re bleed the whole system...the leack may not only leal out fliud but suck moisture back in.

Std brake fluids are highly hydroscopic (absorb moisture) this moisture then reacts with the fliud to form hydrochloric acid...this then reacts with metal parts, in particular those of Aluminium alloys.

99% of problems with the hydrolics in brakes are caused by not strickly following the above rules...Thu the maynot appear at the time, they WILL appear a yr or 2 down the road.

[Forumadmin]

The chances of water ending up in the wheel cylinders on a Jup or Javelin filled with Silicone are negligible as the lowest point is the master cylinder and that is where all the crap ends up. I maintain that very little water will get into the system anyway; but it is worth cleaning the master cylinder every couple of years to save the piston and seals from wear.

Since water is absorbed by the glycol it will distribute itself everywhere, including the wheel cylinders. If you drive your Jowett so hard you reach the boiling point of water, then this absorbed water will boil and the brakes will become spongy. Note the boiling point would be higher than 100c because of the fluid pressure. The steam would condense very quickly as it reached the cooler parts of the system. It is unlikely braking would be affected very much.

[Robin Fairservice]

I would not be so sure that boiling water in brakes would not be a problem. A few years ago there was a fatal accident at the MIRA test track which involved a older model sportrs car that lost control during high sped braking. The inquest report sstrongly suggested that water in the brake fluid had boiled in a disk brake caliper causeing serious instabiltiy during the braking process.

[Forumadmin]

Just changing the fluid does not remove the debris in the master cylinder; best to dismantle. The problem may not be so bad if everything is new, including the reservoir. You will get more rust in the system with glycol because it holds the water.
Although Pat is correct at full yump a wheel cylinder will be lower than the master cylinder, pipes go upwards from the master cylinder to feed them. As Pat suggests water may enter the system from the reservoir especially if washed with a power washer.
Interested to know whether the MIRA car was on silicone. They were disks which suffer more from brake pressure changes than drums.
I have had brake fade many times on rallies before I changed to competition linings. I do not think the fading was ever caused by fluid boiling; but I do not know.

[Robin Fairservice]

The MIRA car was probably using conventional fluids as this was a few years ago and apparently the fluids had not been changed for many years. I read about this in a Classic car magazine, and it was printed as a warning to people to change their brake fluids.

[dougie]

Hi Robin,
Changing the brake fluid is something we all should do but avoid.
A pressure bleeder is the go,just an airline fitting in the top of a spare res.cover and apply a couple of psi to it and you can bleed the brakes on your own.Just don't run out of fluid!
That was a great drive together from Armidale to Brisbane,I enjoyed you're company very much.

[PAUL BEAUMONT]

Is anyone going to answer Paul's question on brake pipe ends???? From my experience our friends the other side of the pond stick doggedly to Imperial threads - Unified not British threads, and I am not familiar with the Javelin braking system to know which are needed ( its the Bradford, with which I am most familiar, and it does not suffer with hydraulics problems!)
I wonder if there is a USA car parts specialist in your area Paul, or whether any USA Jowett owner could help??

[paul wilks]

I thought I should let you all know about my trials and tribulations re my Javelin brakes. So here goes and I'm afraid the story is far from a conclusion.
Firstly a confession, since it's good for the soul. I cross threaded(!) one of my wheel cylinders as I was fitting the pipe and could not stop the leak. I was supplied with a replacement and then realised it bore a different Girling part number to the one already fitted. It was then I discovered that there are two cylinders which look identical but which have different size piston bores. Now I realise that ALL of you will know this already but please bear with me.
My Javelin has full hydraulic brakes and I have always specified this when obtaining brake parts. Many years ago I requested and was supplied with wheel cylinders for all round and simply fitted them and forgot them (until my latest experience with a seized cylinder that is!)
My car has Girling part number 303310 wheel cylinders on the front offside (right hand). I have been told that these are for the earlier hydro-mechanical Javelins and have a 1" piston bore. Apparently I should have Girling part number 303200/210 which have a 7/8" bore. I assume the wheel cylinders fitted to the left hand side will also be 1" bore although I haven't yet had the heart to take that hub off as well!
This is a real pain since I had assumed (in my undoubted ignorance) that replacement of a wheel cylinder was going to be pretty straight forward.
My dilemma now is:
Should I go to all that added expense of replacing all front wheel cylinders to the 7/8" piston bore variety?
Would it be safe to try to source a 1" piston and fit that and run on 1" piston brakes with a full hydraulic car?
Could I run the car with say one 7/8" piston and one 1" piston as long as I "mirrored" this arrangement on the opposite wheel?
Does anyone know where I could obtain a Girling 303310 (1" piston) wheel cylinder please?

Thanks everyone for your patience and concern. I'm almost at the end of my tether with this additional Javelin problem.

Paul

[paul wilks]

I have been since told that my 1" cylinders are NOT for the earlier hydro-mechanical cars since they don't have two pistons but only one. The current 1" cylinders are just like the cylinders in all the parts brochures etc. for full hydraulic braked cars! So did Jowetts fit both 1" and 7/8" piston bore wheel cylinders to full hydraulic braked cars at some stage since they seem interchangeable?

[David Morris]

Dear Paul,

This a very complicated picture! What I understand to be the usual position is that for a full hydraulic Javelin, ie after chassis E0/PB/10594, the following should apply :-

Front Cylinders ( Left Hand ) are Girling 390320 [ these may have casting numbers H3115 or 303200W marked on the side of the cylinder] The Jowett part number was 54195.

Front Cylinders ( Right Hand ) are Girling 390321 [ these may have casting numbers H3116 or 412670 marked on the side of the cylinder] The Jowett part number was 54196.

Rear Cylinders are Girling 390120 & 390121 [ these may have casting numbers 301210W or 301200W marked on the side of the cylinders, according to them being RH or LH] The Jowett part numbers was 54209 (LH) and 54210(RH).

According to measurements I have made this evening, the front cylinders and the rears are both 7/8â€

[paul wilks]

Thanks David.

What a fool I have been! Following your advice I removed the near-side hub this morning and hey presto both cylinders on this axle bear the Girling number 303200W and do in fact appear to be 7/8" dia. So how did I get supplied with 7/8" for the front near side and 1" for the offside when I renewed all my wheel cylinders and master cylinder many years ago? Added to which all appeared to work very well.

Well I think the failed (1") front offside wheel cylinder has in fact done me a favour since it has brought to light a potentially dangerous situation re the brakes on my blessed car.

I will now be able to order 7/8" front cylinders in complete(??) confidence.

Tghanks for all your help.

Paul

[Keith Andrews]

The Javelin in the Clund Shed under resto is getting ready to have brakes installed....Im just a by stander on the project..
The cylinders had been honed but there is a question on 1 as it if is ok...marginal
The philospy is "brakes, take no short cuts, do so and u die"
The descintion by Neil Moore, after some discussion..get them all reselved in stainless.

[paul wilks]

My suspicion is that MY offside cylinders of 1" dia are not for a Javelin and were NEVER intended to be. It will be interesting to see which car they were intended for!

By the way, the body of the 1" dia cylinders DO look that bit bigger than the correct 7/8" dia cylinders when placed side by side although they are the same overall design and worryingly they DO fit the Javelin backplate- no problem and they work!

If my experience helps others then I will be glad. I never realised replacing a wheel cylinder could be so complicated and traumatic! But at least I will have the correct cylinders at the front. Next job will be to check the rear cylinders!

Paul

[paul wilks]

I have found a source for Javelin wheel cylinders- Paul H.Hunt of
POWERTRACK LTD. The 'benefits' are: the price £32.50 and (AND in my view this is more important) the fact that no cylinders are required for exchange. This will help me to have at least one spare per wheel should I encounter a similar problem in the future!

The down side is that the cylinders, whilst they are new, are not made by Girling but Powertrack have helped in the develoment and remanufacture of these units which have been obsolete for many years. Presumably they will also never be made by the Lucas Girling.

They have advised me that they have sold hundreds of these cylinder all over the world and they are popular with many clubs and specialists.

My questions are:

Has anyone in the JCC had experience of these Powertrack 'remanufactured' cylinders?
What guidance could/would you give me, please?

Thanks

Paul