BN2 Master Cylinder

[bighealeysource]

Hey y’all,
I have been working on getting better brake pedal pressure after switching brake cylinders on right side, front and back. Bleeding the brakes and no air in the lines, but still not much for a pedal. Wondering if maybe I need to prime the master cylinder? Has not been messed with, but is 15 years old or so. Not leaking as far as I can tell. Any thoughts?
Thanks,
Mike

 

[John Turney]

If it hasn't been rebuilt in 15 years or so, I would think it should be done. That's a long time for DOT 3 or 4 brake fluid.

 

[bighealeysource]

You recommend just rebuilding versus a new Girling unit ? Boot on my mc loose and no grease in it as supposed to be per workshop manual. Imagine innards not much better. Going to take advantage of Moss free shipping deal that expires tomorrow?

 

[kodpkd]

Also. I have had good luck with the motive bleeder. It hooks to the reservoir, 10 psi, one person bleeding. What year is the car? Some of the older Healey's the cylinders at the wheels are upside down and might require reverse bleeding.

 

[bighealeysource]

Well, I tried my Motive bleeder again at 10 pounds. Hardest part of using it is getting a good seal on the brake reservoir, but got that
done using yellow gas sealing tape. Anyway, pumped it up, went around and bled all corners, jumped in the car, and had a great
pedal. BUT, took off the Motive bleeder, took car off of the jack stands, jumped in, and no pedal. Have to pump it four or five times
to get any pedal. NOW what do I do ? Have not rebuilt the MC yet, but ordered the kit from Moss. I am at my wit's end !

 

[kodpkd]

It sounds like a bad MC. They are not that hard to replace, at least in the 61 BT7. You can reach it from below. two bolts, two lines, and the pedal.

 

[bighealeysource]

Whole braking problem started with the left rear wheel cylinder freezing up so replaced and then had to bleed the system. I honestly had not checked on the master cylinder in ages so my bad there. Rubber boot was totally dry of the red girling grease but had been working up until now. I bled the system 3 times today and no air in the brake fluid so guess the MC has just crapped out !

 

[Bob_Spidell]

I had the same symptoms and a new M/C--a TWR--didn't solve it. What finally worked is pumping up the pedal, then pressing and holding pressure with something (I put a suitable length of 2x4 propped against the seat pan hard against the pedal). The next day, I had good pedal and it's been good since. Don't ask me how/why this worked--maybe forces any dissolved gas out of the fluid--but it did.

 

[bighealeysource]

Thanks Bob ! Like one of the other guys said on another similar thread, I'm about ready to put chicken bones underneath and
chant voodoo sayings to get it to work. So, I will try your fix today and see what I have tomorrow !!!

On another topic and as you have a BN2 also, what do you do to get a tight seal with the trans drain plug ?

 

[kodpkd]

That would certainty be worth a try before replacing the MC. One other thing I thought of when bleeding. With the Motive hooked up and the bleeder open, I pushed the pedal slowly through full travel. The goofy way the MC is designed, this could help push bubbles out of the MC.
I see now that you have a BN2. The cylinders at the wheels are upside down, I would try pressure at the wheels, pushing fluid back up into the reservoir also.

 

[Bob_Spidell]

...

On another topic and as you have a BN2 also, what do you do to get a tight seal with the trans drain plug ?

My traditional go-to has been Permatex Teflon Thread Sealant (Loctite has something similar). I see that now there are a lot of variants--and the price has gone up, natch--but this works pretty well (I use it on the diff plug as well). I figure if any gets loose it won't plug anything up, like Teflon tape might.

https://www.amazon.com/Permatex-59235-Temperature-Thread-Sealant/dp/B000AAJTYS/ref=asc_df_B000AAJTYS/?tag=hyprod-20&linkCode=df0&hvadid=242122067968&hvpos=&hvnetw=g&hvrand=3011703898759475611&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9032278&hvtargid=pla-504163537407&psc=1

I see now they have a 'High Performance' variant, even more expensive (it might work better):

https://www.amazon.com/Permatex-59235-Temperature-Thread-Sealant/dp/B000AAJTYS/ref=asc_df_B000AAJTYS/?tag=hyprod-20&linkCode=df0&hvadid=242122067968&hvpos=&hvnetw=g&hvrand=3011703898759475611&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9032278&hvtargid=pla-504163537407&psc=1

This stuff is (semi-)permanent. It sealed a sloppy plug fitting on an 'uprated' water pump when nothing else, short of brazing, worked (I wouldn't use it on a gearbox of diff plug):

Permatex Seal + Lock Threadlocker Gel 1.18 oz - Ace Hardware

Permatex Seal + Lock Thread Compound is a one of a kind product that combines the power of a thread sealant and a threadlocker into one. Current products on the market can only seal or lock, but Permatex has created a revolutionary product that does both. With this hybrid thread compound, sealed...

www.acehardware.com

 

[bighealeysource]

I had the same symptoms and a new M/C--a TWR--didn't solve it. What finally worked is pumping up the pedal, then pressing and holding pressure with something (I put a suitable length of 2x4 propped against the seat pan hard against the pedal). The next day, I had good pedal and it's been good since. Don't ask me how/why this worked--maybe forces any dissolved gas out of the fluid--but it did.

Tried the 2 x 4 trick last night and still no pedal ! If I pump it up 4 or 5 times I get some pedal, but as soon as I take my foot off of the brake
pedal, it will go back down and start over again. I have checked all the fittings, even broke connections on the front brake hard line between the cylinders to in theory let any air out there, even replaced the right rear hard brake line ( I had bunged up the brass fitting going into wheel cylinder).
I've reverse bled front brakes, gravity bled all four, out of ideas !

 

[mezy]

Tried the 2 x 4 trick last night and still no pedal ! If I pump it up 4 or 5 times I get some pedal, but as soon as I take my foot off of the brake
pedal, it will go back down and start over again. I have checked all the fittings, even broke connections on the front brake hard line between the cylinders to in theory let any air out there, even replaced the right rear hard brake line ( I had bunged up the brass fitting going into wheel cylinder).
I've reverse bled front brakes, gravity bled all four, out of ideas

One way I have bled brakes is to open the bleed screw, physically collapse the two pistons close the bleeder, then allow the pistons to come out on their own. Repeat until clean air-free fluid comes out of the bleeder.

I have found that sometimes, especially with an older master cylinder, it is not a good idea to depress it too far.

 

[kodpkd]

Tried the 2 x 4 trick last night and still no pedal ! If I pump it up 4 or 5 times I get some pedal, but as soon as I take my foot off of the brake
pedal, it will go back down and start over again. I have checked all the fittings, even broke connections on the front brake hard line between the cylinders to in theory let any air out there, even replaced the right rear hard brake line ( I had bunged up the brass fitting going into wheel cylinder).
I've reverse bled front brakes, gravity bled all four, out of ideas !

call me

 

[bighealeysource]

call me

Be glad to - email me your number to

 

[BobHaskell]

You might try clamping closed the flexible lines to determine if the problem is with the front or rear brakes, or not.

 

[red57]

If I pump it up 4 or 5 times I get some pedal, but as soon as I take my foot off of the brake
pedal, it will go back down and start over again.

One question - when you 'pump it up 4 or 5 times' does the pedal become hard as well as higher? or is it still soft/spongy but higher?

I ask because air compresses and fluid doesn't so if you pump up and it gets hard/firm as well as higher, that indicates no air in the system and it's probably a question of adjustment. If it pumps up and is still soft/spongy that indicates air in the system.

The springs on the shoes pull the shoes back to the resting position - but when you pump quickly, the shoes don't have time to make it all the way back to 'rest' before the next pump so the shoes progress further and further with each successive pump, ie contacting the drums sooner resulting in a higher pedal. Then when you stop pumping the fluid to returns to the reservoir, and the pedal is low again.

So for me, it's a question of how hard is the pedal when it pumps up, because that's how you know if its air or adjustment.

Just my .02

 

[bighealeysource]

You might try clamping closed the flexible lines to determine if the problem is with the front or rear brakes, or not.

Wish I could, have stainless brake lines so cannot clamp them.

 

[bighealeysource]

One question - when you 'pump it up 4 or 5 times' does the pedal become hard as well as higher? or is it still soft/spongy but higher?

I ask because air compresses and fluid doesn't so if you pump up and it gets hard/firm as well as higher, that indicates no air in the system and it's probably a question of adjustment. If it pumps up and is still soft/spongy that indicates air in the system.

The springs on the shoes pull the shoes back to the resting position - but when you pump quickly, the shoes don't have time to make it all the way back to 'rest' before the next pump so the shoes progress further and further with each successive pump, ie contacting the drums sooner resulting in a higher pedal. Then when you stop pumping the fluid to returns to the reservoir, and the pedal is low again.

So for me, it's a question of how hard is the pedal when it pumps up, because that's how you know if its air or adjustment.

Just my .02

Hey Red57.
I wish it was a hard pedal but at best when driving it, takes 4 or 5 pumps to get enough pedal to slow it down and stop. Certainly not a hard pedal. Had a nice chat with kodpkd about brake woes and came up with a couple of ideas. Going to pull drums on front brakes, clamp the wheel cylinders fully closed, and see with a motive pressure pump and/or reverse bleeding see if I can get any possible trapped air in that bass ackwards system.
Going to do something similar on rear brakes and make sure brake cylinder piston is fully retracted and pressure bleed the rears.

 

[kodpkd]

I am not sure what the rule is,,,, but when I adjusted the rears, I turned the adjuster until I was at the, 1/4 turn flat, where the drums were tight, then backed them off just one 1/4 turn. I could tell that the shoes were just barely touching.