• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Brake Trouble, again

Share this page

M

Mack

Senior Member
Offline
I had made an earlier post about brake pedal fade, and had good answers back, but the pedal fade is back and I think along with replacing the flex lines to the front calipers I'm gonna change the brake lines altogether. Here is my question, I have a spool of new brake line, but if I remember from a midget I used to own, the brake lines have a "double flare" at the ends, is this the case with my '76 B ? If so, Sears sells a double flare tool for about $40.00. Second question, is that the tool I need to do that? Any help and/or suggestions would be great. Thanks, MACK /ubbthreads/images/graemlins/cheers.gif
 
I could be wrong, but I think you need ISO/bubble flairs on your brake lines. A double flare is folded back onto itself //, whereas a bubble flare is bent away /\

Snap-On and better tool retailers sell the correct tool; you'll need to practice to get a decent flare.

When I restored my B, I bought a new set of CNC pre-bent preflared hard lines in stainless steel from Classic Tube & Line. They fit *perfectly*. About $200 a few years ago.
 
I can't offhand remember which flares you have. I almost want to say double flares.
I would reccomend buying or borrowing a Snap-on flaring tool. I've never had luck with the cheaper ones. If you get the Double flare tool you can "cheat" the bubble flare by only doing the first step... But I really think you will find they are all double flares.
Be careful not to over-torque the flare nuts or they will mushroom out and then they don't want to ever come out again.
 
Just curious, why you want to replace the hard brake lines? I don't think pedal fade would be caused by hard brake lines. Old rubber lines, could do that but usually they cause a soft pedal, but not fade. If the seals in your master cyl are starting to wear, fluid could leak by without actually leaking out onto the ground (or your right shoe as the case may be). That would cause the pedal to fade.
 
To me the term "Brake Fade" is due to the material the lining is made of heating up and decreasing the ability of it to stop the car.
If you are refering to the brake pedal going lower as you hold pressure at a stop light for instance. This is usually caused by the master cylinder leaking fluid past the piston.
At least that has been my experience.
Bob
 
To clarify the pedal fade is as you described, the pedal goes to the floor with steady pressure, where would I look for the master cylinder leak if this was the case? I would assume if I took the top to the pedal box off or not? I don't have any obvious leaks and the fluid hasn't gone down much, but I marked the resovoir with a pencil to make sure. Could it be that I haven't gotten all the air out of the lines? The brakes seem to stop fine as long as I pump the pedal. Thanks for all the help MACK
 
Hi Mack, The MC does not have to produce a visible leak for it to be defective.The description you give of "Brake Fade" fits MC defects to a T. You can try rebleading the system but I doubt that is your problem.On the other hand, you could be drawing air into the system somewhere but in that case I would expect to see a visible leak at that point---Fwiw---Keoke
 
Sounds like the master cylinder is leaking internally (not holding pressure). There will be no visible loss of fluid or change in the fluid level.
 
Yes, the leak I was talking about would be no visible external leak. It is going past the piston internally. The rubber around the piston gets hard and it wont hold back the fluid. I have had several MC's do that over the years and it takes rebuilding it or a new one. I found mine easier to replace the last time the MG did it.
I would make sure you tried all else before doing this such as checking fluid levels and bleeding. Also make sure you don't have any leaks anywhere else.
Bob
 
I didn't address the statement you made about pumping the brake makes them work. This is another symptom of the MC causeing the problem. The rubber will push against the side of the cylinder enough to make the brakes work under hard pumping up the pressure but because the leak past the piston is a slow leak and the hard rubber is not as effective at sealing at smaller pressure so the fluid leaks past.
Bob
 
Hello all, Thanks for all the secondary responses, it sounds to me like the MC is in need of rebuilding/replaceing. Has anyone done this? I have a good shop manual(not the Haynes) that describes the rebuild in good detail. My mechanical skill is decent, but getting better thanks to folks like you! Is this better left to "experts" or can the average individual handle it? To be honest it doesn't look all that difficult, keeping parts clean and spotless seems to be key, any suggestions or insight would be great and thanks again, I'll keep a post on how I'm making out. MACK
 
The main problem with rebuilding any cylincer is honeing the cylinder until every last pit in the surface is gone. You need to be meticulas with this or the new rubber will tare at the pit and leak very soon after the rebuild. The few I have tried this with (wheel cylinders)required an awful lot of honeing. So you need to weigh the time involved and what your time is worth. I have tried a MC but it has been so many years, I can't remember the reason for my eventual choice of buying a new one. Obviously the choice resulted in not having to worry about for all these years now.
Pits are caused by moisture in the fluid and by mentioning this I am opening it up to an awful lot of different opinions on this involving what kind of fluid to use. I have used silicon fluid for many years and my frequency of rebuilds went way down. Most of the guys here use Dot 3 or Dot 4. Of those two choices I wouldn't go with anything but Dot 4 because of the experience I have had with both. Dot 3 has lasted the least amount of time in my car before a cylinder would fail. The British rubber won't last long in it. But that is a matter of opinion very strongly argued here in the past.
Bob
 
Bob, Is there a special tool for honeing the MC? If not what did you use or what would you recomend? Also I beleave I have been using DOT3 in my brakes, but will change to DOT4 after reading your last post. Can I drain the brake system as best as possible and then change over to the DOT4? Or are the two not compatable Thanks, MACK
 
While I put on my flame preventing propeller cap.. I have NEVER had a master cylinder, or slave cylinder, OR caliper go bad on me. EVER. I have had to hone and/or replace those on cars that I hvae purchased.. Matter of fact, the first thing I do on a new classic car is tear down the hydraulics.

I use DOT 4 all the time, and I (I'll say this slowly so everyone here can follow along) B-L-E-E-D my hydraulics as per the maintenance schedule.. for all my cars.. It's really easy to do, especially when you install those nifty one-man bleed screws. Sure, they're $10 a pair, but heck, a new master for my MG is how much?

Regular maintanance is a must.. It cures faulty electronics, bad brakes, gremlins, and all sorts of things that plague our sweet MGs.

Good Luck
 
Mack, there are brake cylinder hones available at autozone and other parts stores. That last one I got was from autozone and is a good 3 stone one that you can adjust the amount of pressure on the stones I bought I believe for $19.95. I used it on my clutch slave cylinder though and the bore is bigger than the MC. Like I said before, I don't remember the reason why I didn't rebuild it last time but it may have been the hone I had was too big. I can't remember though. I believe the MC cylinder bore is around .7 inches so make sure the one you buy will go that small.
I have an old model plane fuel syringe I use to take the old fluid out of the master cylinder so just take all the dot 3 out you can and drain the system then flush completely all the way through with dot 4 by bleeding the system. Then throw the old fluid away. Don't use the syringe to put new in just pour it from the can.
Bob
 
I too am having brake troubles on my '59 MGA and '47 TC. My own fault. They have been on blocks since summer 1987, and now that I want to get them both road-worthy, the rear brakes are siezed up. I've tried everything I can think of (including "get a bigger hammer!") and have only gotten about 1/2 inch toward getting the drum off. I would re-adjust the brakes but the adjustment hole is not at the cylinder adjustment screw and I can't rotate to it as the brakes are siezed up. I could sure use some suggestions! /ubbthreads/images/graemlins/frown.gif
 
HI Duane, are the engines running???---Keoke
 
Bob, thanks for the help, I've ordered the MC rebuild kit and am attempting to locate the honeing tool, and plan to to the MC ASAP, keep ya posted. MACK /ubbthreads/images/graemlins/cheers.gif
 
Duane, Keoke responded about the engines running, I would assume this is on the order of first things first?? But I had the same trouble with a different vehicle, I had to put a gear puller on the drum and rap the outside of the drum with a hammer before it broke loose, and if I remember there was quite a loud ping when it broke loose, don't know if it will work but just a suggestion, Good luck, MACK
 
Back
Top