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BJ8 with servo...Brake travel issue

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rcflyer

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I am fighting a frustrating issue on brake pedal travel. How far down on the first press of the pedal should it go??? Mine goes down..maybe 3 inches, then if I immediately let up & go again it goes down maybe 2 inches. My MGA is only about an inch every time and brakes are super. Significant bleeding has occurred, I put 3 bottles through. It is NOT using brake fluid,I Rebuilt calipers, new rubber hoses..BUT nothing has been done to the rear brakes (the linings look OK). One thing I noticed is according to the photo in Moss catalog and the factory manual the lower shoe is on backwards (both sides). Thanks, Lee
 
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Here is a photo of the rear brake (I have not done anything to them yet)...Looks like the lower shoe may be on wrong? Will this cause any issues? Lee
 

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It is my understanding from reading the parts books & manual that the Master for the brakes should be 7/8 and Healey Surgeons say you can see that the casting is larger on the brake than the clutch (3/4)...mine looks the SAME. I ordered a Master cylinder , new shoes, various other small parts and new springs for the rear.We will see if this fixes the issues. Also, I see the brake booster is a Lockheed and looks pretty new (relatively speaking) so someone has replaced it along the way. Whan I bang on it with a rubber mallet I hear NO fluid inside and I don't see white smoke from the exhaust, so I think it is OK. Any comments welcome...Lee
 
Having one rear shoe on backwards won't make that much of a difference. The lining is shorter by about an inch on the leading edges of the shoes to make them 'self energising' so if one is on backwards then the braking force will be slightly less.

An easy test for finding where movement is occurring in a brake system is to pull on the e-brake then press/release the pedal once. Next application should be with reduced travel if the rear brakes are causing problems as the first press pushes the wheel cylinders out to their brakes-applied position. Even with the shoes adjusted correctly there still seems to be some movement in Healey rear brakes as two cars I have done this year gain about 1/2-1" pedal travel with the e-brake off. Neither has bedded in the shoes yet though.

Also, be aware of some resellers supplying replacement shoes that are dangerous because the lining is so thin that the wheel cylinders can pop out and cause complete loss of braking. Has happened to two people on this list so far, have a look in the archives. Andy.
 
Andy, Thanks for all the info...I just ordered all the misc parts from Moss but ordered the shoes & springs from Healey Surgeons. Hope there are OK. Actually the shoes on there are 3/16 but worn a little unevenly (inner side is worn more than outer. I also ordered new (4) felt tips for the shoe positioners (the ones that align the shoes perp. with the back plate. I will replace all the worn parts and adj everything up...then the rear should be good to go either way. Maybe the Master is the issue (I just ordered a TRW (Girling) one from Moss). I did some measuring and the difference in first stroke vs 2nd/3rd stoke is about 1 inch. Thanks, Lee
 
Put the linings on correctly before you do anything else. The distance between the lining surfaces the way your linings are is not even - too close on one side, and too far on the other. Then readjust and you should feel a difference.
good luck, Bob
 
Bob, Thanks for the info...I have new parts arriving tomorrow. I will get everything all fixed up correctly and see if it fixes the issue. I think it WILL....today for fun...I used a couple small C clamps and held the wheel cylinders from moving...seems the first pedal push only goes down a little further than the next push now. So, I'm hopeful the new shoes, springs, and EM brake clevis pins (some idiot had put in small bolts/nuts instead of new clevis pins some time ago) will take care of all this..I do have a questionfor all of you... on my MGA 1600 my brakes pedal only goes down maybe 2 inches before full pressure(I rebuilt the ENTIRE system when I got the car) How far down should a BJ8 with servo go down for full pressure what all is normal???, Thanks, Lee
 
OK guys...an update..Today I received the parts. In looking at the Master Cylinder..it is quite a bit LARGER than the one on the car. So I suspect the car has a 3/4 on it instead of the 7/8. I will change that out. As to the rest of the story, I received new shoes for the rear today and they have thinner linings than came off the car. I have no idea what wheel cylinders are on the car, so I ordered new ones from Healey Surgeons. According to them the new wheel cylinders NEED the thinner lining shoes for clearance to the drums. They have 3 different thickness linings available based on our needs (Thanks to them for doing what they can to help out!) , BUT what the heck! We are fixing one thing to fix a screw up by another here! I have read here about the possibility of popping a wheel cylinder by using the thin linings...What?? That should never happen, I may be new to Healeys but not to doing brake jobs. The wheel cylinders should never have the piston out far enough for that to happen...even if the shoes are worn all the way. I am going to see when I get these parts what's up. I will see how much max throw the cylinder has, and shim the shoe/piston so it barely goes on the drum to see where the piston will wind up and compare to the max stroke to see what the margin is. I may keep the cylinders that are on the car or replace with the new ones?? It looks like based on what I was told by HS that the correct thickness lining depends on the wheel cylinders you have (and my comment...maybe how much the drums have been turned?). Kind of crazy I think. I'm off to the garage to work. Thanks, Lee
 
This BJ8 (with servo) has the wrong Master Cylinder in it. The new one I just got is considerably larger in diameter. I am going to replace it today. Thanks, Lee
 
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Well, this is getting frustrating. The Master Cylinder I received from Moss is too big to fit in the firewall. I didn't take the old one out as it looks very obvious now that I take a close look this won't fit. The dia. is much larger than what's in there. It should be the correct one for my car. I have a 1965 BJ8 Mark III with a brake servo. (built in Sept. 1964). Wander what's up? I think when you have the servo it is supposed to use the larger (7/8) cylinder?? Thanks, Lee
 
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I appreciate your frustration and all you have done to date as I experienced a similar issue.

What brake fluid are you using?

I ask this because the resolution to my similar issue turned out to be the elimination of air that may have been absorbed by the Silicon during the initial fill. Silicone brake fluid is prone to absorbing and during the initial fill and later release it requiring another bleed. I would not be surprised if you could be experiencing a similar condition and either a little air still remains in your system.

To further this thought, a good friend also experiencing the same peddle travel problem on his BN4 after a full brake system rebuild and fill with DOT3. Although he repeatedly bled his system, pushing close to a gallon of fluid over at least a month, peddle travel was still less the second time. Now questioning everything he did, he decided to shake up the system with a very short bumpy ride around the block. Upon returning, he again fully bled the system and now extracted a small amount of air. The result, peddle travel was finally consistent and where he expected...

Last, although you may have a smaller then correct MC installed, I would not be too fast to conclude until measuring. A 7/8” bore is not much larger than a 5/8” bore found in a BJ7 and should not result in a much larger external measure.

Just some thoughts,
Ray (64BJ8P1)
 
Ray, Thanks for the response.....OK...I am using Dot 3. One thing I found and corrected was the lower shoes, both sides (rear of course as this is a BJ8) were on wrong. On the forum here one person said it would not matter much and one said fix it as it would. Since I have fixed it, and replaced the clevis pins in the EM brake and adjusted it for 8 clicks full lock, the pedal travel seems better. My first throw is slightly more that the next, but it only goes down about 3 inches. It seems that is too much?? but I am comparing it to my MGA 1600 which has about an inch before good brake pressure. The brake Master Cylinder is exactly the same Dia. as the Clutch. The correct?? one I got from Moss is obviously much larger in Dia. I double checked with Moss and it is the correct P/N. I have not pulled the MC but it looks to me that this new one won't go in the hole. In healey BJ8 production the 7/8 MC came along with the change to have the servo in every car (1963 ish) Since mine is a 1965 (built in 9/64) Something is off here?? One of my friends said when he lost his servo, rather than replace it...he installed the smaller 3/4 MC so pedal pressure would be a little easier to use?? Someone here has to know the story on all this???, Thanks, Lee ALSO how come I can't get any extra spaces by using return(enter) on my posts??
 
rcflyer said:
Ray, Thanks for the response.....OK...I am using Dot 3. One thing I found and corrected was the lower shoes, both sides (rear of course as this is a BJ8) were on wrong. On the forum here one person said it would not matter much and one said fix it as it would. Since I have fixed it, and replaced the clevis pins in the EM brake and adjusted it for 8 clicks full lock, the pedal travel seems better. My first throw is slightly more that the next, but it only goes down about 3 inches. It seems that is too much?? but I am comparing it to my MGA 1600 which has about an inch before good brake pressure. The brake Master Cylinder is exactly the same Dia. as the Clutch. The correct?? one I got from Moss is obviously much larger in Dia. I double checked with Moss and it is the correct P/N. I have not pulled the MC but it looks to me that this new one won't go in the hole. In healey BJ8 production the 7/8 MC came along with the change to have the servo in every car (1963 ish) Since mine is a 1965 (built in 9/64) Something is off here?? One of my friends said when he lost his servo, rather than replace it...he installed the smaller 3/4 MC so pedal pressure would be a little easier to use?? Someone here has to know the story on all this???, Thanks, Lee ALSO how come I can't get any extra spaces by using return(enter) on my posts??
Click to expand...

You can also use shift-enter to skip a line.

Can't you take calipers and measure the size of the opening on the inside above the pedals.
 
The BJ8 should have the 7/8" master for the brakes. The rubber boot might have to come off the outside of the cylinder to get it through the hole, but you can leave it on the rod as you pass it through. Then put it back after the master is in place.
Good luck, Bob
 
From my experience Bob is correct, the rubber cap must be removed to insert the MC through the firewall and reinstalled from the inside. Also, when bolting the MC to the firewall, don’t forget to install the 2 spacers. .

From my experience and what I have read, a BJ8 with Girling Brake Servo will have more peddle travel than an earlier Healey not so equipped. However, peddle travel should be consistent for each application of the brake.

Steve is correct and the task is doable but, I believe would also require removal of the piston retaining clip (not the piston). If I were uncomfortable with the unit installed and had a new correct part on hand, I would just go ahead and replace the old with the new. If the old unit turns out to have the correct bore, I would consider rebuilding it at a later date and hold it as a replacement.

All the best,
Ray (64BJ8P1)
 
Steve, Bob, Ray....thanks a lot for the help here. What spacers? I see in the Moss catalog that there are 2 packing pieces listed (gaskets I think) are these what you speak of? In looking at my car I see no spacer or gasket on the Brake Master. I do see it on the clutch...so I assume P.O. did not put them in. I don't have any so I will order them. The NEW Master I have here (came from Moss) is a TRW , says Lucas on the side and is 1.3 inches in dia. and the place where it goes in the firewall is 1.35 in. Dia. Seem very large...but if you guys say it will go in...I will plan to install it. If I remove the boot on the old MC I wander if I could tell if it is a 5/8, 3/4, 7/8...I will try to see which it is. I can tell you for certain that it is exactly the same Dia. on the OUSIDE as the clutch. It is probably a 3/4...which I guess really is OK. I assume they went to 7/8 when they installed the servo to get more fluid from the MC to operate the valve on the servo. Probably to reduce pedal movement needed., Thanks, Lee
 
Steve, is that in decimal (.875 as example) ?? Also, yes it is a Girling I 'll get out my mirror and have a better look see. , Thanks, Lee.....Also, I still can't figure how to get a blank line while posting (tried Shift, enter)
 
rcflyer said:
Steve, is that in decimal (.875 as example) ?? Also, yes it is a Girling I 'll get out my mirror and have a better look see. , Thanks, Lee.....Also, I still can't figure how to get a blank line while posting (tried Shift, enter)
Click to expand...

It'll be right there on the side - totally obvious. It'll say 87 or 875
 
Steve,
Good catch. It’s a heck of a lot easier looking for the numbers on the outside of the MC then getting on your back in the close confines of a BJ8 drivers side dash, taking the cap, rod, and retaining clip off, and then trying to properly position and read the micrometer.
Lee,
I stand corrected, however, it does space the MC back so the peddle/rod does not push the piston further than its design limit.
Wow, you may have hit on the possible cause of your problem.
As I understand, when the brake peddle is applied, the seal at the end is pushed in place to stop fluid from flowing back to the reservoir and the spacers assure that this seal will stop at its designed location. Without the spacers and with aging seals more prone to deform under pressure, a small amount of fluid could be leaking back into the reservoir on the peddles first application. Since the wheel brakes would now be closer to their destination then on the first application, the requirement for additional fluid for the reasonably-immediate second and following applications of the peddle could now appear consistent in travel length.
Conclusion, change the MC and install the packing spacers.
Just a thought,
Ray (64BJ8P1)
 
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