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Big trouble with BN4 brakes

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Larry, Wow...nice photo clip! OK here is what I have learned...As many of you know I have been involved in a somewhat similar issue. My pedal would go almost to the floor (still had brakes) 1st time, then 2nd time if done fairly soon about 1/2 way down and plenty of brakes. After lots of bleeding etc. no help. As a side issue I took the car to Fox/Fox a very experienced shop for alignment. I told the guy to be careful as the brakes go down on the 1st attempt, but it was OK to stop the car. He did the alignment (toe in was out 1/4 inch) then when he returned the car said my brake issue is not hydraulic but rear brakes and/or EM brake issues. I got home and really took a look at how it works. I discovered that the EM brake setting is the home position of the rear shoes on the cylinder end and the brake adj. is the home for the other end. The position of the rear EM brake determines how far the piston has to travel to get the shoe against the drum. The EM brake mech are spring loaded to pull the EM brake levers back from the drum. IF the EM brake is way too loose the home position makes the piston/shoe way back from the drum and the amount of movement for the shoe to contact the drum is a LOT more than it should be. After discovering this (I know many of you know this already) I decided to put a small C clamps on each wheel cylinder and test the brakes (Since you can't see inside the drum to watch). Wah-Lah the pedal did not go way down any more. I discovered while doing all this the PO put small bolts in the places the 1/4 " clevis's go ...so I ordered new ones. I also discovered the PO had installed the lower shoes backwards. I re-did the shoes, clevises and adj the EM brake for 5 clicks to lock, re-adj the rear brakes last...then found the excessive pedal movement was gone. My pedal goes down about 3 " 1st and 2nd times now. I also found the PO had put in a 5/8 instead of 7/8 MC, so my travel is more than it should be (I have a 7/8 now to install). I don't know if the front drum brakes would be suseptable to extra slop due to linings too thin, or cylinders made wrong ect....but I have leaned to eliminate mech. issues just put a C clamp on and see what the hydraulic's do then. So if you put on 6 C clamps on a BN-4 and the pedal is fine...the issue has to be MC or air (assuming hoses are OK). Also, I have a set of new wheel cylinders in my hand and I don't like something about them. When I did my MGA...they had little rubber bands on them to keep the pistons in...these do not AND the pistons stay in...WHERE is the spring that pushes the piston out to be sure it seats on the shoe??? (my MGA cylinders DO have a spring) I wander if all those wheel cylinders you have on your car are not made right? IF they were like this one the piston would retract back in spite of the rear brake EM setting or other brake adjustments?? Maybe the pistons stay out once fluid is in there...but I'm used to a spring being in there.Food for thought, Lee
 
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...... Maybe the factory realized, "hey, this is not a good set up" and changed the hydraulic system.
so, that's our story, and we're sticking to it :smile:
the Healey when everything was working![/QUOTE]
Hi Larry
I agree with you, I read your post as very similar at my AH100/6 experience, the variant was that I have turned to Front Disks MOD - Long time loss and TWO experienced mechanics work, to have a MC that don't
need two pumping action, changing MC and rear wheel cylinders I have finally a good brake system, BUT not
a hand brake right work (car was stopped only forward) and needed more works on rear shoes adjustment, and now the brake system is very good-
the end of story is that I have a lot of spare parts for brake,
me and the two experienced mechanic if inquired never can said what was wrong, sure the rear brakes are critical.
Children that came in the vicinity, learn a lot of new words
 
My fault for the confusion...Sorry...Larry and I had similar issues at the same time and I was helping him based on what I learned working on my BJ8. Bruce at HS was also helping me (parts & talk) with the issue I had at the same time. Rear brakes are the same (I think) and that is where most of my issues were., Thanks, Lee
 
steveg said:
/confusion. IIRC - rear cylinders are different (larger, I think) on the disc-braked cars in order to act as a proportioning device.
Click to expand...

With the front DISK MOD.on 100/6 rear cylinders must be the SMALL Ghirling for BN7 BJ7 Bj8, learned this from hindley reply at my inquiry from Magnus of BORA's,
strong recommendation NOT use economic cylinder reproduction,present on supplier catalogs (my self learned lesson)
Cheers
 
I have 2 new cylinders from Moss, in the catalog they say they are Girling, but they say TRW (I heard TRW bought Girling??) on them and they say made in Taiwan. At least TRW is a good company and I would hope they watch quality. They were $ 70. each. According to Moss catalog they are correct for a BJ8., Thanks, Lee
 
Hi Lee
TRW quality aren't in discussion I have one TRW MC on car and is OK
my warning is refereed to the rear cylinders that cost just half of Ghirling (+/-20 GBP each) that haven't the required dimensions for the thin shoes -
my flip out at the first attempt....too short -- don't worry my machinist easy modify it -but cost go to Ghiling level- and time was lost-
 
Andrea, I have a TRW MC, AND 2 TRW rear wheel cylinders, all from Moss. The TRW rear wheel cylinders did cost twice as much as the after market they sell. Please give me the detail on this issue of thin shoes?? I got a set of shoes from Healey Surgeons and they are 2 MM thinner than were on the car (not worn much but uneven, so I want to change them) and they said they had 3 thickness's available based on the wheel cylinders. I was just going to return them...and take my old shoes and drums to a local re-liner shop (top quality) and have him make them the same as the old ones and arc the linings to the drums. He will also take a few thousands off the drums for a nice surface., Lee
 
Hi Lee
In my battle for have brake at efficient level - I have acquired:
4 x new rear brake cylinder (the first couple are the regular 100/6 RBC-the second couple was machined to have the correct excursion)
2 x new rear brake drum (in alternative at my oldest couple-I have find that old have only 1mm more in diameter- I think that wasn't my problem solving)
3 x new Master Cylinders(one regular 100/6 MC3/4-one 5/8 MC - and finally a 7/8 MC)
1 x new couple of brake shoes ( I have find that my oldest have 1 mm more thickness)

The first issue was the B pedal to floor at 1st attempt and good at 2nd
solved changing MC to 7/8 and BN7 Bj/7 RBC - (probably system work also with 3/4 MC- but I am exhaust after the battle, and happy for the results-- NO more experiments!)
The second issue was that Hand brake is efficient only forward solved only after a laborious work on rear shoes trim

now with a efficient brake system I think that the
1st problem was solved changing the rear BC to BN7 BT7 cylinders
2nd problem was only due to elimination of all the complessive excess of play in the HBS and trimming the shoes handle
also NOT forget that Brake System need some road running work to gain the correct rear shoes adaptation
If you have also Hand brake problem- I have find that AHead4Healey UK have on catalog Long and Short link bar handbrake-linkage-Short.jpgwith regulation- that can help to avoid excessive play and incorrect shoes thickness
Cheers
 
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I had a excessive travel in my E brake handle and it turned out the mount was broken inside the tunnel, allowing the whole mount to rotate before the brake engaged. Handle at 11-o'clock position.
handBrakeBrace.jpg Added the reinforcing brace, clamped to the frame.
 
steveg said:
I had a excessive travel in my E brake handle and it turned out the mount was broken inside the tunnel, allowing the whole mount to rotate before the brake engaged. Handle at 11-o'clock position.
View attachment 30125 Added the reinforcing brace, clamped to the frame.
Click to expand...

I had the same problem but solved it by having a local welding shop weld it up for me.
 
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