BN2 Master Cylinder

[kodpkd]

Any luck?

 

[bighealeysource]

Any luck?

Hey Kevin,
Had company this past weekend so didn't work on the Healey. But did double check on the master cylinder being "bench bled" in place as did it again and now ready to start trying all the other things that have been discussed trying to get my brakes back ! Stay tuned, I'll get back with
an update/s.
Mike

 

[kodpkd]

My brakes are pretty good,,,,,, BUT after replacing rear cylinders, MC, front pads, and extensive bleeding I still get a little better pedal if I double pump the pedal. I am going to try bleeding the rear cylinders. My thought,,,, maybe there is still a bit of air trapped up against the rear cylinder piston or the rear shoes don't fit properly against the arc of the drums. The first pump pushing the shoes up against the drum, second pump tightens them up for braking.
There are three different pedal issues you can have. 1,,, When the pedal is pushed, it will slowly go down. This means your MC seals are shot and fluid is leaking around the seals, or you have a leak. 2,,, The pedal is spongy/soft, you have air someplace in the system. 3,,,, Having to pump the pedal to get it to the top. Something in your system needs to be pushed into position, shoes or pads, before you get a high pedal.

 

[bighealeysource]

Is there a fourth issue as right now I push on the pedal it simple goes all the way with little resistance ? And this is after bleeding the
brand new TRW master cylinder again.

 

[kodpkd]

Just to be sure...... The line from the reservoir goes to the rear port on the MC. The line to the wheels comes from the forward port on the MC.

 

[kodpkd]

Your MC looks like this?

 

[bighealeysource]

View attachment 86823
Your MC looks like this?

Yep, that be it. Line from reservoir goes to yellow inlet and to hard brake line to red inlet.

 

[kodpkd]

I'm going to remove the rear drums, squeeze the pistons all the way and see if I get any air from the cylinders.
I am really stumped why you are not getting ANY pedal. I have been thinking little picture and big picture.
I am still thinking the goofy way the front system is made there is air there.
Just looking at the front system,,,, I can see there could be an issue with reverse bleeding the front,,, or the rear for that matter. Any air in the wheel system would have to go through the MC and into the reservoir,,,, not a good thing.

 

[bighealeysource]

Hey Kevin,
Going to try the process of removing the front drums, fully retracting the pistons in the cylinders, and seeing if that works as has been suggested
by several 100 owners. If it warms up enough today will try it this afternoon.

Did price out cost of the disc brake conversion kit from AH Spares and just over a $1000 right now plus about $150
shipping to SC from UK. Almost to that stage of changing out the drums to discs on front even if it is a 100M. I'll keep the drums, etc but
improve my braking and circumvent that bloody Girling design.
Thanks
Mike

 

[kodpkd]

With the drums off and the cylinders compressed be very careful the amount of pressure you apply to the system. I am going to start with the Motive hooked up and try 1 psi first and go up from there. You don't want to pop the pistons out of the wheel cylinders.

This is good.

Bleeding Austin Healey 4 Wheel Drum Brakes – Precision Sportscar

precisionsportscar.com

I wonder if anybody has tried reversing the bleeder screw and the short line on the back side of the front brakes. This would put the bleeder screw on the upper part of the cylinder where air will be. The same with the rubber hose on the other side. Are the threads the same?

 

[bighealeysource]

With the drums off and the cylinders compressed be very careful the amount of pressure you apply to the system. I am going to start with the Motive hooked up and try 1 psi first and go up from there. You don't want to pop the pistons out of the wheel cylinders.

This is good.

Bleeding Austin Healey 4 Wheel Drum Brakes – Precision Sportscar

precisionsportscar.com

I'm using Michael's article as my guide. Might use the c lamps to make sure the pistons don't pop out as recommended in same article.

 

[kodpkd]

I think my double pump was because of the rear brakes. I compressed the cylinders at the rear wheels with a set of C clamp vice-grips, they compressed just a tiny bit. Not sure if this would have made any difference. I used the Motive bleeder at the reservoir, 5 lbs. I did get a large bubble from the left rear. I bled them compressed and not compressed. I have had a set of new shoes on the back for a while. I think they are breaking in. I was able to adjust them, one 1/4 turn tighter. I turned then in, in 1/4 turn increments until I could feel the drum tight as I turned it, then 1/4 turn back. Be sure the adjuster is in the center of the 1/4 turn, just a little bit either way will tighten the shoes against the drum to much. After a test drive where I applied the brakes a dozen times, I felt the rear drums with my hand and they were still not warm. No more double pump, and I think they are not as spongy. I think the double pump was because rear shoes weren't broke in and not adjusted correctly.
I hope you can find your bubble!

 

[bighealeysource]

Well, I have made some progress on this beast of a problem. As described before I have tried everything to get my brakes back.
So this latest round I pulled the front brake drums, removed the brake shoes, and compressed the pistons fully back in and held
in place with C clamps, being cautious to put a small piece of wood between the C clamp jaw and the piston. Pressure bled all
corners, even gravity bled for good measure. Now I have brakes if I do 3 quick pumps on the pedal where before I had zero
brakes. So making progress. Going to try the "stick holding the pedal down overnight"trick and see if that does anything.

 

[kodpkd]

Did you remove the drums on the rears and compress the cylinder? It is twice as big,,, double pistons.
The fronts are self adjusting by the springs in both of the cylinders. Do these work? How do you compress the shoes to slide the drum on?
The rears definitely need to be adjusted correctly after bleeding. Are these adjusted tight then one click back?
Did you see bubbles in the bleed tube?
I stand corrected,,,,,,,, there IS an adjuster on the front brakes. There are two eccentric adjusters on both front wheels. Have you adjusted these tight?

 

[bighealeysource]

Hey Kevin,
In process of checking rear wheel cylinders. Done left side and after compressing it with a C clamp did get some small air bubbles out so
going to do the right side since that cylinder was also replaced. Maybe this will improve things !

 

[kodpkd]

I think the thing that helped me the most was to adjust the shoes as tight as you can and still have the drum being able to move. I think your issue with the pedal going to the floor and having to pump pedal, the shoes have to much space to move until coming into contact with the drums. The springs on the shoes pull them together, while the pistons try to push them apart for braking. If there is to much distance from the shoe to the drum, the pedal will go to the floor. I haven't seen on your posts that you adjusted the 4 spiral adjusters on the front brakes.

 

[bighealeysource]

I think the thing that helped me the most was to adjust the shoes as tight as you can and still have the drum being able to move. I think your issue with the pedal going to the floor and having to pump pedal, the shoes have to much space to move until coming into contact with the drums. The springs on the shoes pull them together, while the pistons try to push them apart for braking. If there is to much distance from the shoe to the drum, the pedal will go to the floor. I haven't seen on your posts that you adjusted the 4 spiral adjusters on the front brakes.

Hey Kevin,
Takes two pumps now so making progress. Right rear brake cylinder had no air in it so got it all back together for the umpteenth time
and now going to try your suggestion on adjusting the brakes as tight as I can and still move the drum. All adjusters are working as
took them all apart, cleaned up and put some red Girling brake grease on them. I have adjusted the 4 spiral/snail front brake adjusters.
Stay tuned,
Mike

 

[kodpkd]

I think you will succeed.
Spongy pedal = air
Double pump = adjustment.

 

[kodpkd]

Anything?

 

[bighealeysource]

Anything?

Getting ready to work on it today! Wish me luck.