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Brake problem

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H

higgins

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I have a major brake problem which is baffling me :crazyeyes:

I installed a new master brake cylinder as I had a problem with the pedal traveling too far and only on pumping would the pressure build up.

With the new cylinder it's gotten much worse

The pedal now travels straight to the floor and after pumping the pedal twice the pressure builds up.

The 4 Drumbrakes on my 100/6 are adjusted an I cannot find any leaks anywhere.

I've bleed the brakes now for the 3rd time with more than a liter of brake fluid but no change.

Any help is more than welcome :bow:
 
Hi frustrating problem. However, you may have to bleed the master cylinder its self to correct the problem.Fwiw--Keoke
 
Which new cylinder did you install? There is a new, premium 'gold' something-or-other cylinder which has been giving people trouble.

Have someone work the pedal slowly while you watch the fluid level in the reservoir. If the fluid rises with a pump then the reservoir supply shutoff valve is damaged/not working (I believe that is the problem with the new cylinders).
 
I recall reading on this forum that it is a good idea to put teflon tape on the bleed screw threads to prevent air from being drawn back into the brake lines during the bleeding operation. Haven't done it myself, but makes sense.
 
Nev,

I'm pretty sure the consensus was that was not a good idea. The best approach is to open the bleed valve under pressure and to close it before the fluid stops coming out (ie, while your friends foot is still in mid sweep, pushing the brake pedal to the floor board)
 
Keoke said:
Hi frustrating problem. However, you may have to bleed the master cylinder its self to correct the problem.Fwiw--Keoke
Click to expand...

Hey, when I say it first, you have to quote me and then say "I agree." I think it is a law or something. :hammer:
 
Check the time, keoke was typing while you posted :laugh:
 
Hi Nevets,

I appreciate your frustration. I experienced the same difficulty when John Sims and I tried to clear the air from his 100/6 brakes after installing new lines and a master. After over three months of bleeding (I think he went through a gallon of fluid) we still had a falling peddle that would recover after a few pumps. Although each bleed would expel a few small bubbles and developed a hard peddle, by the next day the peddle would again fade to the floor.

The issue disappeared after we drove the car to a friends garage who, again, expelled air from the system. My thought is that the jostling ride caused the trapped air to move to locations conducive for bleeding. My suggestion, after all fails, find a safe time and place and drive the car through a few turns and see if you get additional air out of the system. It may take a few runs.

Good luck,
Ray (64BJ8P1)
 
Sure am glad I dont run into the troubles a lot of you guys here do. When I rebuilt my brakes, replaced all of the rubber in everything. Polished the bores in the aluminum parts, and blew out all of the lines. Next I bled the master cylinder, then cracked all four of the bleed screws open just slightly. Made a bunch of short strokes slow and easy with my foot. I could hear and feel the air being pushed out as the pedal started to get solid. When the pedal was hard and had little travel, I simply tightened the bleed screws. Sometimes its difficult to find a third hand right when you need it, and gotta improvise to get things done occasionally. So far so good.
 
Legal Bill said:
Keoke said:
Hi frustrating problem. However, you may have to bleed the master cylinder its self to correct the problem.Fwiw--Keoke
Click to expand...

Hey, when I say it first, you have to quote me and then say "I agree." I think it is a law or something. :hammer:--OK OK OK!!! ---------------------- :lol:
[/quote

Thanke TIM--------------------------------Keoke
Click to expand...
 
If you are bleeding the brakes on your own, I have a little weeze that works for me. Get a couple of metres of clear tubing of a size that fits snug over the bleed nipple, If you have a lighting stand or a something tall, drape the tube over that, so it is raised in the air and you can see it from the driving seat. let the bottom end go into a container in case of over shoot, open the nipple and then pump the brake. You can let the fluid come to the top of the bend in the tube and run it to waste or just stop just short of overspilling. You can see the bubbles rising in the fluid. When you stop pumping the fluid will fall back to come level with the resevoir and pumping can continue. You can then tighten up the nipple and move on to the next wheel. I have actually glued 2 metres of a smaller bore tube into a short length of the 5mm tube? so that the amount of fluid wasted is less if you see what I mean.

Bob
 
Bleed the master cylinder (I agree, I agree, I agree...).

I use a short piece of brake line with a fitting on one (1) end, and bend it so that the open end of the tube goes below the fluid level in the reservoir.

The M/C MUST be bled prior to bleeding the rest of the circuit(s) (or else!).

A brake pipe about to be sacrificed for the good of the car:

IMG_3227.sized.jpg


Pipe directed from the M/C to the reservoir:

IMG_3228.sized.jpg


Clutch M/C shown in this example:

IMG_3229.sized.jpg


Make certain to direct the return stream to the chamber you're drawing from:

IMG_3232.sized.jpg


My First Choice in British car brake fluid:

IMG_3234.sized.jpg


I use this method for 1-man brake/clutch bleeding:

IMG_3250.sized.jpg


Beware of two (2) different types of fittings when working on BJ8s!

IMG_3247.sized.jpg


IMG_3248.sized.jpg
 
Legal Bill said:
Great idea Randy. I have some nice brake line ready to be repurposed.
Click to expand...
"Repurposed"?

You've been watching too much HGTV (sure, blame it on your wife...).
 
Randy,
Where are those 2 different fittings used on a BJ8?
Are you connecting the "out pipe" from the M/C to your bleed pipe to create a circular flow? If so, when you connect the normal pipe from the "out port" to the slave/rest of brake system, how do you prevent either fluid from draining out or air from re-entering, or is this not an issue since the fitting is on the top of the M/C and you're about to bleed the rest of the system next.
thanks,
rich
 
I too had the same problem on my bn4 and am interested to hear what you discover. I still haven't solved the problem. I replaced the master cylinder with 3 different m/c's (2 new, one rebuilt), replaced all brake cylinders with new ones from Moss (front and rear), new relined shoes, new flexible hoses (all 3), new brake switch (thinking that was the culprit), and still I have a pedal which falls the floor after I get a solid pedal pumping the brakes a few times. I've since not worked on the car in frustration for a few months, my next plan was to pinch off each flexible hose to at least isolate the problem front/ rear/ side, and possibly replace the front brake hoses with stainless lines. I have no visible leaks. I too have gone through a lot of brake fluid trying to chase down the problem.
Please let me know what you discover!
Good luck.
Austin
 
Austin , You may not have an air problem in your system! Tighten all six adjusters up as tight as you can( lock each wheel) then see how your pedal is. Take shoe movement out of the equation . New shoes that aren't worn in to match the drum will have to move further hence the pumping. I had a BN4 , had the same problem . Even adjusted right , still had to pump the brakes once to get full pedal. Since you make no mention of whether the new shoes are arced to their drums , this would be my first guess before Moss runs out of new master cylinders to send..... good luck.
 
I would try a different brand of brake fluid as not all dot 3 or dot 4 are not the same even though it has that rating . You want a high number of cinitastokes which is thicker the lower stuff is made for the newer brake systems. You will need to find the detailed spec sheet for the fluids you wish to try. Stay away from anything that says ABS

Cheers

Mark
 
Like the other guy said... I am fortunate that I don't have these problems with brakes. An automotive 4 wheel drum brake system with a single line master cylinder is about the simplest you can find , other than cutting a hole in the floor under your feet . Don't let it get the best of you !
 
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