Brakes problem

[fredsajs]

Hi,
Has anyone any helpful advise on my Berlie brake concerned problem.
It appears to have a somewhat flaw whilst I am stationary with engine running.
With engine on tick over and foot on brake- peddle with handbrake off, the peddle seams to loose presure and foot goes to floor, but car does not move.
Also notice that the car does pull up on heavy braking but peddle low down.
Pumping peddle has no effect !.
There appears to be no leaks of fluid and all rubber hoses to servo are new and air tight.
Any help would be greatfully received !.
Thanks

[Dane_Rescueman]

Re: Brakes problem

Hi Fred,
Check again for any fluid leaks at every join and hose, then for weeps from the calipers and rear cylinders.

If this is OK then ask an assistant to look at all flex hoses as you apply firm brakes to check for bulges or balloons.

Have a jolly good grope around the top of th brake pedal and the rear of the master cylinder. Leaks can occur here, but, a loss of fluid would show in the reservoir.

During this it may be a good idea to re-bleed all the brakes. It is possible a spot of air could cause a similar problem.

Does the problem happen with the engine stopped? With the engine stopped, press and release the brakes until the servo vacuum is dissipated. Press hard on the brake pedal and hold. Does it still sink to the floor? This would not be a servo fault.

If the pedal remains firm and does not continue to sink then start the engine whilst keeping the pedal depressed. As the vacuum builds up the pedal should sink a little and stabilise. If it doesn\'t change then the servo or it\'s valve may need work.

Sometimes the valve can wear in the vacuum servo but normally this causes fluid to be sucked in to the intake manifold so you would notice a loss of fluid and possibly a slightly smelly and light smoky exhaust.

If this is all OK then the problem could be an internal leak in the master cylinder. You can sometimes see little bubbles appear on the surface of the fluid in the master cylinder reservoir whilst applying and holding the brakes on. It does not always happen. This will not lose any fluid from the reservoir but it just seeps from one side of the piston to the other. There are a couple of springs in my twin circuit master cylinder. One broke many years ago and caused a similar problem.

So, what we are looking at here is probably an internal fault with the master cylinder.
I suggest a master cylinder repair kit or a new master cylinder.

As a final straw clutching thought! Have you recently changed the master cylinder? The standard (cortina) Berli needs the master cylinder push rod to be shortened before insertion. It is fitted with a Marlin produced Pedal fitting. The instructions are in the build manual. I can email you the diagram if this is the case.

Good luck with it, Danny knows a lot more about this than I do so if in doubt ask him for help.

[fredsajs]

Re: Brakes problem

HI Dane,
Havent changed m/cyl as still orignal build.
Will check on other ideas,re no engine running try peddle tryed this no differance just stays low and as engine starts starts to sink.
Will advise.
Thanks
Fred.

[greyV8pete]

Re: Brakes problem

If the pedal starts to sink as the engine starts it shows that the servo is working. Have you thoroughly bled the system? If you system is dual circuit and one line has air in it the pedal will go down a long way until the push rod makes mechanical contact with the floating piston. I had a similar problem with my old Sierra. Had to use both Gunsons Ezibleed (pressurised gadget) PLUS pumping the pedal hard to get rid of the air. Brakes were rock solid after that. Peter.

[csjcarolyn]

Re: Brakes problem

Hi Fred,
If you have no external leaks it sounds like you have something called BRAKE PEDAL CREEP. This is where the master cylinder\'s high pressure seal leaks back into the reservoir. IF this is what you have you MIGHT get away with new seals but a new master cylinder is always best.

Roger

[fredsajs]

Re: Brakes problem

Hi All,
Thanks for advise will proceed with all your tech: tips and advise later.
Fred.

[macdonald.dm]

Re: Brakes problem

I suspect - as Roger says - that the master cylinder seals are worn. With a heavy stamp on the brakes all might appear to be working ok, but with steady pressure on the pedal, the fluid simply seeps its way past the worn sides rubber piston seals, and the piston sinks down the bore.

IF you can get a repair kit and IF you have clear instructions in, say, a Haynes manual and IF you are absolutely confident tackling such a critical component, then a repair is quite possible. Otherwise a reconditioned unit might be best.

What is your Berli based on? I\'ve just sold on my Cortina Mk3 manual but have a Sierra one. If there\'s info in there I\'d be happy to scan it and email it to you as a pdf file if that\'s any help.

[fredsajs]

Re: Brakes problem

HI Donnie,
Thanks for confirming what I had thought but was hoping for some easer problem, but such is life,I have all books but thanks for advise and help, Berli is a Cortina original built based kit.
Fred

[macdonald.dm]

Re: Brakes problem

Blimey - a quick search on eBay for \'Cortina Master Brake\' returned 19 items! Looks like a fair selection of complete units for around £20 and repair kits from 99p!

I did this repair job many moons ago and recall it was very straight-forward. You just need be absolutely clear about the direction the seals are facing (make sure the Haynes diagrams/photos are completely unambiguous - sometimes \'dished\' seals can \'change\' direction like an optical illusion!) and the sequence of fitting. Get everything perfectly clean, have a good gander down the bore for wear marks (chuck it if any) and use plenty of brake fluid during assembly.

I think you\'ll find it a very satisfying task!

(And don\'t forget paint doesn\'t like brake fluid...)

[cabrioman]

Re: Brakes problem

Best way to check the master cylinder Fred is to check it with the engine off.

Pump the pedal a few times to get a solid hard pedal then take most of the pressure off just apply VERY light foot pedal pressure, if its the master cylinder, the pedal will sink slowly to the floor under very light pressure.

John

[fredsajs]

Re: Brakes problem

HI,
Thanks for info.
Nursing damaged tennions on left knee so out of action for a while.
Thanks anyway.
Fred.

[James]

Re: Brakes problem

Hi Fred,
Hope you\'ve checked your right knee, it might otherwise be the root of your brake troubles!! Joking apart, one thing I remember reading in Pitstop a few years ago was that a member warned about a failed weld on the brake pedal. If I remember rightly the weld holding the stub onto the pedal (the stub that the servo rod fixes onto) had failed causing long pedal movement and eventually total brake failure. It might be worth the effort for you to take a look. The other thing that springs to mind is that wrongly adjusted rear brake shoes can also demand excessive brake pedal travel, have you checked your rear brakes?
Good luck with the knee and brakes!
James

[fredsajs]

Re: Brakes problem

Thanks James.
As you say joking apart, I have convinced myself its master cylinder seals in duel servo system.
However a strange picture thought has emerged that also might hold a problem that perhaps somone can shed light,.
The resevior plastic unit is mounted on top of master cyclinder with the filler cap at bulkhead end. Thus making reseviour slant downwards, causing levals to slop away from entry fill point. Can any one confirm wich is correct mounting way round for this unit to mount to mast/cyclinder,as no pict in handbook, as I didnot build it !.
Many thanks. Fred.

[macdonald.dm]

Re: Brakes problem

Hi Fred.

Looking at pics of my engine bay, the servo vacuum chamber and master cylinder look to be horizontal which makes the reservoir on top slope at an angle as you say. I can only guess that in the donor Cortina the bulkhead the servo was mounted on to was sloping slightly making the reservoir level but the servo and master cylinder pointy upwards!

I'm guessing this is a pretty standard Marlin feature and can't see it being the cause of your problem; I dare say the slope means that one of the master cylinder inlets could become exposed to air a little more early than in the Cortina, but it would have to be nearly completely dry of fluid before that happened!

[fredsajs]

Re: Brakes problem

Thanks Donnie.
I had notice a somwhat lowness in the resivior to nearly clear one entry point just below filling cap, which seam to be caused by angle of resivior tank horizontal mounting on top of horizontal mounted m/cycl, which made me ask the question.
However you didnot clarify which end your filler cap was on brake m/cyclinder resivior. Was it near the bulkhead or near the alternator ?.Many thanks.