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100-6 front drum brakes?

Chet Zerlin

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Hi all,

Once again I need to reach out to the many knowledgeable people on this forum for help with a frustrating issue.

Whenever I use my brakes on my 1959 100-6 BN6 I always have to do a quick pump on the brake pedal first to firm up the pedal. If I don't it goes almost to the floor before the brakes are fully engaged. My brakes have been completely rebuilt, there is no air in the lines and the shoes are properly arced to the brake drums. The shoes are properly adjusted. All work was done by a mechanic who has an excellent reputation and is very knowledgable. I have even tried the "lock pedal down with a stick and leave overnight" solution with no result.

I've been told that the initial soft pedal I am experiencing is because the front drum brakes on my BN6 each have two wheel cylinders (one on each end of the brake shoes) whereas I'm told that most drum brakes have only one wheel cylinder and a spacer/adjuster that is fixed and does not move. I've also been told that because of those two cylinders, whenever I release the brake pedal both cylinders retract resulting in greater "play" then in a brake system with only one wheel cylinder. The suggestion is that taking up this increased distance before both cylinders push the brake shoes to fully engage the drums is what I am experiencing when I first push on the brake pedal. The quick pump thus taking up the play in the system and resulting in no play for the second pump. Adding credence to this explanation is that the quick pump does work and I have to do that each time I use the brakes.

Before I decide to just live with it or bite the bullet and spend $$ on changing to front discs I would like to hear from others who have stock 100-6 brakes to know if they have the same brake configuration as I do (two vs. one wheel cylinder) and if they do are they experiencing the same issue (and if so how did they "fix" it)?

Thanks!
Chet
 
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I know of other vehicles of the same era with twin brake cylinder drum brakes that do not need to be pumped first when properly configured (some Series Land Rovers).

Assuming your brake lines are bled of air, have no leaks, that the brake fluid is new (i.e. has not collected water over time; brake fluid is hygroscopic), and that there is nothing else in the lines that must be compressed with the first pedal pump prior to the hydraulics behaving as they should - your brakes should be stiff and responsive.

All of the above is not necessarily "easy" to achieve.

Mechanical assumptions I can think of are that your master cylinder is working as it should be, and is the correct master cylinder for the number (and size) of wheel brake cylinders in the system..

In short, there's nothing fundamentally broken about twin cylinder brakes.

But.. maybe there's something different about Healeys that I'm not aware of..?
 

DerekJ

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The two cylinders are there because the brakes are a twin leading shoe system which is more effective than single leading shoe which is what the back brakes are. Properly set up there should be no difference in feel between the two. There is a problem with your system, air is getting in somewhere. You just have to go back to basics and thoroughly purge the system. Don’t decide to just live with it.
 

red57

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Derek is correct - There is a problem with your system, don't decide to just live with it (and there is no need to change to discs).

Although if it "firms up" after a quick pump (and gets properly firm) that could be adjustment rather than air in the system.

Normally when there is air, the air compresses and causes a soft pedal - a 'quick pump' will not remove the air. The pedal may come up because pistons have been moved closer to the shoes and/or slop has been taken up, but it won't get firmer because the air is still there. On the other hand it may just 'seem' to get firmer after a quick pump and it may still be soft, just higher.

But either way, your system is not right and should be able to work as intended.

Dave
 

Roger

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Derek and Dave are right. Be thankful you came to this forum rather than listening to whomever advised you!
 

Healey 100

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My 100 with similar drums does not do this. I am sure ur problem is with the master cylinder. Not so clear how those work but they do when set up properly. Make sure the cyl retracts completely when brakes release. There are tiny ports that need to be open to refill it from the reservoir. It takes close inspection to find and clear them. Also mismatched rubber parts can cover up bleed ports.
 
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pkmh

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I have to assume your problem is not the result of your brake cylinders for the moment and if it is, then I cannot quality to offer an opinion since my Healey is a BJ8 without that setup.

However, what I can offer as an opinion is something I experienced on my first Healey (also a BJ8) where I made extensive repairs to practically most of the brake system and yet afterwards, I had a very similar problem of having to pump the pedal as you are having. In my case, I had installed a new brake master assembly at the time with one new double flared brake line connection to it. I later discovered the brake line leading from the assembly did not provide an air tight seal, but the kicker was no obvious sign of leakage or air was visible, except for a very small, "bearable" amount of fluid emanating from that brake line seal. Having a friend over and pumping the pedal while observing all connections helped me to see just enough of this evidence.

My additional thought is, maybe coating the surrounding line seals with a dab of brake fluid is see if, after pumping the pedal, would reveal slight fluctuations at one or more these connections. When I discovered this breach, I redid the connection, and my problem never came back.

Just one possible thought. Good luck.

Paul
 

Dandare

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I seem to remember that this problem was to do with air being trapped in the link pipe between the two cylinders...the top part of this pipe being higher than the cylinders. there is a procedure to deal with it and as soon as I remember what it is I will post it!

I think it involved bleeding in the conventioal way (tube on the bleed nipple/ pushing the pedal) but having the bleed receptacle higher than the link pipe.

Danny
 
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Chet Zerlin

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I seem to remember that this problem was to do with air being trapped in the link pipe between the two cylinders...the top part of this pipe being higher than the cylinders. there is a procedure to deal with it and as soon as I remember what it is I will post it!

I think it involved bleeding in the conventioal way (tube on the bleed nipple/ pushing the pedal) but having the bleed receptacle higher than the link pipe.

Danny

Danny...if you remember and post that solution it would be greatly appreciated!
 

steveg

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Didn't Randy Forbes post on this before - regarding loosening one of the tube nuts on the crossover pipe?

IMO using a syringe to pull the fluid out the bleed screw would handle an air pocket in the pipe.

Am using silicone fluid, but would not casually change to it without doing it as part of a complete overhaul and flushing of the brake system.
 
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There's only two (2) possibilities, assuming no faulty components__like a failing m/cyl__either you still have air in the system, or the shoes aren't close enough to the drums in their "released" position.

When I still had the drums on the front of my BN6, I had a MUCH FIRMER pedal, with barely an inch (1") of travel to ROCK HARD standing on the brake pedal. I still cannot get the MKI disc brakes to that same state (though switching to s/s-Teflon hoses made a noticeable improvement).

Yes, in an effort to thoroughly bleed the circuits, I'd crack open the pipe connecting the twin leading shoe wheel cylinders__it's been over thirty (>30) years since I fitted the discs__so I can't say that I remember every aspect of setting up the 4-whl drums.

When I'd adjust the shoes, I would bring them just to the point of "touching" the drums, but not dragging on them; they may not have even touched throughout the entire revolution. I'd do one (1) of the front shoes to where I wanted it, then back off one (1) "click" and do its mate. When satisfied with the second (2nd) shoe, I'd put the one (1) click back into the adjustment of the first (1st) shoe. Adjust the rears similarly (just touching, not dragging).

Operate the handbrake a couple times (then release it fully) and check the rear brakes again. STAND on the brake pedal a few times, then go around and check each wheel that the shoes are still just touching the drums, but that none are dragging. All wheels should rotate with about the same resistance, though at the rears, you're turning the axle & driveshaft, etc. (xmsn should be in neutral while adjusting rears, or you're turning both wheels).

Take it out for a drive, and use the brakes enough to get them up to normal operating temperature, then get all four (4) wheels in the air again to verify that none are too loose/too tight. If you have an infrared temperature gun, get a reading off each drum the second you get out of the car, looking for any that may be hotter than the others; an indication of the shoe(s) dragging.

If there are braided stainless steel/Teflon flexible hoses available for your car__with 4-whl drum brakes__then I recommend you fit them. They made a noticeable improvement, reducing pedal travel, when I put them on my car (stock 3000 disc/drum).

Final thoughts; are you certain that every component is sized correctly? When I got my car__>40 yrs ago__the rear wheel cylinders were different sizes! I don't think there's a choice for the four (4) front wheel cylinders (I only remember them being big, maybe 7/8" or 1" in diameter) but the rears were different depending on all drum or disc/drum. The master cylinder is also available in different sizes, depending on drum/drum, disc/drum & disc/drum w/servo assist (as concerns all pre-BJ8 disc/drum setups).

In closing, I don't think there is anything wrong with keeping the 4-wheel drum brakes, and the only thing I possibly gained by converting mine was perhaps a reduction in weight (can't remember the values now, but I did weigh everything when I did the swap). The ONLY time I experienced the front (rear) drums used hard enough to fade, was one night when I was accelerating DOWN Steiner Street in San Francisco, and slowing at each cross street (pretending I was Frank Bullitt, perhaps) by the time I got to Lombard, I had to really stand on the pedal to get it stopped! But like I said, that was some extreme use that is unlikely to take place even in the most spirited drive today.
 
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Chet Zerlin

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Today I spent the morning following all of the excellent advice I've received here on what and how to check. Clamping the brake hose to the left front brake did not change anything. BUT clamping off the brake hose to the right front brake made all the difference in the world. Clamp off..pedal only hard with a double pump. Clamp on...hard pedal immediately. I did it three times to make sure I wasn't imagining it...
So now on to the next level of diagnosis...Since I used the clamp at the very top and also near the bottom of the brake hose with the same results I'm thinking that the issue is not the flexing of that hose but rather air trapped somewhere in that area of the right front brake system. Since I was by myself I tried using my Mityvac to bleed some fluid hoping that would remove the air but it had no effect.
My guess therefore is that the air is trapped in the pipe connecting the two wheel cylinders - does that sound right?
Randy, could you please share some specifics on exactly how I would "crack open the pipe connecting the twin leading shoe wheel cylinder" and whatever else might be the next thing to try?
Do I fully back off on the two adjusters to move the wheel cylinders in a closed position to minimize the area where the air might be when I do that?

I really feel like I'm getting close to a solution. Any and all suggestions are appreciated!

Thanks everyone!

Chet
 

red57

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Pump up and hold the pedal down and then "crack" or slightly loosten one of the fittings a bit. You can't put a tube on to see the bubbles so you have to listen for the hiss of air escaping. Then make sure you close (tighten) the fitting before raising the pedal.
Just like bleeding through the bleeder valve but at the fitting instead.
I would start with the highest fitting and see if you can hear any air escaping - you will get brake fluid also so be ready to wipe off/clean the area so you don't loose any paint. Then move to other fittings as needed until the pedal is firm. This obviously can be a messy operation but you should be able to get the air out this way.
Dave
 
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Pump up and hold the pedal down and then "crack" or slightly loosten one of the fittings a bit. You can't put a tube on to see the bubbles so you have to listen for the hiss of air escaping. Then make sure you close (tighten) the fitting before raising the pedal.
Just like bleeding through the bleeder valve but at the fitting instead.
I would start with the highest fitting and see if you can hear any air escaping - you will get brake fluid also so be ready to wipe off/clean the area so you don't loose any paint. Then move to other fittings as needed until the pedal is firm. This obviously can be a messy operation but you should be able to get the air out this way.
Dave
What he said!

If you wanted to experiment, I'd adjust the shoes on the faulty brake (RF?) hard against the drum, removing them from the equation. Just be sure to back them off__minimally as possible__when you're done.
 
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Chet Zerlin

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Thanks again! Heading out of town for a few weeks but will try this procedure when i get back home and will report back.

Chet
 

steveg

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Chet - Adding to Randy's comment (maybe I'm saying the same thing) - since you already know the system is good as far as the bottom of the hose, suggest clamping hose there, tightening the shoes tight, then cracking open the adjacent tube nut. If you bought or have a plastic syringe, you could push new fluid upstream from the bleeder screw and force the air out the cracked tube nut. Be sure to wrap the bleeder screw threads with teflon tape, or pack grease around the juncture of bleeder screw threads with slave cylinder body - this will keep outside air from being admitted.

BrakeFtCrossPipe.jpg
 

steveg

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Addendum to above:
Looking at the inside, it appears that backing the shoes all the way off forces the piston inward (arrow). This would reduce the volume of fluid & air in the cylinder to the minimum, making bleeding easier.

Clamping off the hose, cracking the upper tube nut, then backing off the adjusters might have the effect of forcing some of the air out - this before you added any new fluid through the bleeder screw.

screenshot.1494.jpg
 
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