Brake problem

[Mark Cooper]

Just out of interest, what brake master/servo combination are you all using these days? Way back when, the golf system was on the dax. I replaced that with a jaguar master cylinder (drilled) to fit the golf servo. It have me excellent braking but the pedal was very hard.

I recently had to put new jag 4pot calipers on the front of my car, and my braking went all to hell. No reason for it I can see except the new calipers are much smoother in operation (the old ones had begun to stick arount MOT time)

Anyway, the pedal travel is terrible now. I've bled the system a dozen times and no improvement. I've replaced the master cylinder with a new one just in case, still no joy. When I start the car the pedal drops (on its own!) and actually aplies the brakes! A little flick with my foot and it comes back up, but press the pedal and it stays down. The pedal feels really light to as if its not connected. I put a return spring on the pedal, which I never needed before, to fix the dropping part of the problem, but as I'm sure you realise all this does is fix the problem cosmetically--it does nothing to solve the underlying problem whatever that is.

During a test drive of the car, I found that the brakes work, but using over half the pedal travel feels horrible--like I'm not going to stop. It made me drive really tentatively as if I feared ice on the road... I don't want to press the brake pedal I slowed down on the gears a hell of a lot more I can tell you!

Any ideas would be appreciated. I'm thinking of replacing the servo and master cylinder with whatever the standard is that DAX use nowadays just to see what happens. My car is a DAX V12 supertube chassis with the Jag 4pot front and std jag rear calipers.

What do you all use now?

Regards
___________________________
Mark E. Cooper
Impulse Books UK
08707517412 (Fax)
http://www.impulsebooks.co.uk
___________________________

[kdavies3]

Hi Mark, the currently recommended master cylinder and servo is from an Escort MK V. (slightly modified)
From your discription it sounds like you may have issues with your seals in the master cylinder, you haven't changed from regular to silicon brake fluid recently have you? as this causes the seals to go manky.
If all is working correctly, if you start your engine with your foot on the brake pedal it should goo down as the servo evacuates.

HTH

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Kev Davies
Dax, 383ci Chevy Stroker, Tremec TKO
South Wales

:tu

[ian]

Mark, following on from what Kev said, if you switch to the new Ford master cylinder/servo unit, like I did when I converted from V12 Jag to V8 Chevy, you may need a different pedalbox!! I did and was more than slightly pi**ed off that the old pedalbox was not suitable (previously I had E-Type V12 master cylinder and remote servo which was hopeless.) May be worth a call to Dax. It is well-worth the effort and expense in my opinion, when you get it sorted and bled properly (took me ages) it is a superb set up. Mine has improved with mileage, pedal firmed up nicely after just a few miles. Ian.

[Mark Cooper]

Hi Kev,

Thanks for replying. I haven't changed to silicone fluid, but I did replace the master in case the seals were going manky. No improvement in doing this though. Before putting a return spring on the pedal, it went down (physically dropped a couple of inches and could bee seen to do so by the naked eye) without my foot near it when starting the engine. The car wouldn't roll when it did this even when pushed by someone... so the brakes had actually been applied by the vacuum--it wasn't just air being taken up in the cylinder or something equely wierd.

After I get my power steering finished, I'm going to put the Escort servo and master cylinder on the car. Do you use the splitter/safety thingy (what's it called--the thing that splits braking diagonally if you lose braking on one wheel) Do you use that thing, or do you pipe your master cylinder straight to the wheels?

You mention the master cylinder is slightly modified. What does this entail?

Regards
___________________________
Mark E. Cooper
Impulse Books UK
08707517412 (Fax)
http://www.impulsebooks.co.uk
___________________________

[Mark Cooper]

Escort sounds like the way to go. Did you pipe up like in the escort (2 lines to the rear) or did you maintain the jag set up (1 line to the rear)

In what way might the pedal box not be suitable? I currently have the golf servo mounted on the firewall and the jag master cylinder mounted directly on the front of that. The pedal therefore hangs down and connects directly to the rod out the back of the servo. Is it that the rod lengths might be different? If so, it will simply be a matter of bending/reshaping the pedal arm.

I work in a toolroom, so if I have to make a completly new pedal its no big deal... I hope. I obviously would prefer not to do that if i can avoid it though.


Regards
___________________________
Mark E. Cooper
Impulse Books UK
08707517412 (Fax)
http://www.impulsebooks.co.uk
___________________________

[kdavies3]

Hi Mark,
The Dax set up is to pipe a single line to the rear brakes and two lines to the front brakes.
That's from memory antway.

I once had an MGB V8 which had master cylinder problems, as you used the brakes the brakes began to come on more and more on there own until the car would not move. I had to release the pressure from the bleed nipples to get it home. Every few miles.
I had rebuilt the cylinder during the rebuild of the car and I reckon the seals were of poor quality.
I rebuilt the cylinder again with known Girling seals and all was well after that.

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Kev Davies
Dax, 383ci Chevy Stroker, Tremec TKO
South Wales

[Mark Cooper]

>Hi Mark,
>The Dax set up is to pipe a single line to the rear brakes and
>two lines to the front brakes.
>That's from memory antway.
>
>I once had an MGB V8 which had master cylinder problems, as
>you used the brakes the brakes began to come on more and more
>on there own until the car would not move. I had to release
>the pressure from the bleed nipples to get it home. Every few
>miles.
>I had rebuilt the cylinder during the rebuild of the car and I
>reckon the seals were of poor quality.
>I rebuilt the cylinder again with known Girling seals and all
>was well after that.
>

That is strange. The cylinder I put on was brand new from the Jag dealer. Cost a pretty penny to.

You're right about the way DAX designed the piping on my car. One line to the rear, two to the front, but doesn't the escort have four outlets on the master cylinder?


Regards
___________________________
Mark E. Cooper
Impulse Books UK
08707517412 (Fax)
http://www.impulsebooks.co.uk
___________________________

[mclark]

Mark,

I've recently picked up my servo/master cylinder from Dax and yes it does have 4 outlets,
front bottom for brake light switch
front side for rear
the two closet to servo side/bottom are for the front

Regards

Michael

[Mark Cooper]

Ah hah! Thanks Michael for that handy bit of info. My brake light switch is currently a mechanical micro switch on the pedal itself so I didn't know the escort used a pressure switch--thanks.

Someone mentioned the escort master cylinder is slightly modified. Any one know what the mod is? I don't want to go to my local breakers and pick up the bits only to be suprised by it not working for some reason. Also, what about that splitter--anyone using that?

Mark


Regards
___________________________
Mark E. Cooper
Impulse Books UK
08707517412 (Fax)
http://www.impulsebooks.co.uk
___________________________

[mclark]

Mark,

Here's the pic of mine, the mods "I believe" are where the reservoir unions are. On the standard Mk5 the reservoir fits stright onto the master cylinder.

With the Dax offering you get two unions to fit into the top to feed straight to the reservoir.

Regards

Michael



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