Was driving Fiona out to our monthly Mini Breakfast when I detected an brake issue - very soft pedal. Checking the reservoir, I found it to be almost totally empty. I know the last time I checked it (2 weeks ago), it was full and the brakes seemed fine.

I can't find a leak as-is, since the reservoir is empty, but I wonder where the typical leak points are? My plan is to pick up a bottle of DOT-4 fluid, fill her up and then pump the brakes, hopefully restoring pressure (and hopefully re-starting the leak). Obviously, a brake bleed may be required too (sigh).

Thanks as always for any advice!

 

No real typical "leak Points".
Check the calipers...a seal might have gone bad...
Also a rubber line, like the ones that connect the hard lines to the caliper might be to blame...
Or maybe the bleed nuts if they are not on tight on the calipers.....
You just have to look for wet fluid....or other signs of leakage.

 

Would that be generic, or specific to the classic Mini? I assume generic, since the classic has calipers up front and drums in the back.

I started this thread over in the Classics area and it was moved here.

Thanks.

 

Oh good... it came back.

So...

UPDATE: Topped up reservoir w/ DOT-4... can't see any obvious leaks, but pedal is still very soft - I *can* stop, but only with the pedal all the way on the floor practically. Before, I only had to press it 1/3 of the way (if that) to get a nice, firm stop. Guess I might have air in the lines now, since the level was practically nonexistent.

I may get help on this one... Brakes worry me. Actually, it's the NOT HAVING THEM that's worrisome..

UPDATE #2 - A local mechanic advised the rear (drum) wheel cylinders are notorious on the Minis so I climbed under, and sure enough the left side rear drum is damp. There's nothing else back there that wold make it damp that I know of other than brake fluid, so I'm thinking that's my problem...

 

Rear cylinder would be the culprit. A fairly straight forward repair.
I generally replace brake parts in pairs. And given that the other rear cylinder is likely the same age, why not replace it now rather than having to do it in a few weeks/months when it decides to go.

The clips that hold the cylinders to back plates can be fun to install

They can be changed while still on the car but sometimes it's easier to remove the whole assembly and work on a bench.

 

 

Yeah...sometimes they move stuff too fast...any car...same basic places too look!!
From your signature I assumes it was the cabrio....but heck any car's brakes are pretty similar!! I saw it in general...I guess the mods moved it a few times!!

Also you might want to consider using DOT-3 on a classic...it lasts longer, and is better product (more moisture resistant) unless you drive HARD,and you don't have DSC, so the thinner/lower viscosity of the DOT is not needed.

 

I don't drive that hard, so I may try the DOT-3 - DOT-4 is what's specified in the Hayne's book though...

The cylinder repair looks straightforward, but I'm a bit concerned about doing the brake bleed - anyone have any tips? The Hayne's book seems to say it's pretty easy if you have a brake bleed kit, but I've heard different in the real world...

Also, the mechanic I talked to advised that the master cylinder might need a rebuild as well, given the symptoms. What do people out there think? I'm not seeing any leaking or other issues with the master under the bonnet, but I admit I don't really know what I'm looking for...

Thanks!

 

A leaking wheel cylinder caused your problem. Getting air in the lines was the result. Soft brake pedal is the current symptom. That says nothing about the condition of the master cylinder.

I've serviced many different brake systems, but haven't had that pleasure, yet, with my classic, so more classic-experienced users here may be able to tell you if the master cylinders are problematic. The only thing you can say at this point is the master is possibly the same age as the wheel cylinders and thus suspect.

Blake bleeding is a snap if you have either the bleeding kit or a helper (and the bleeding screws on the wheel cylinders will move). Just watch closely and make certain the master doesn't run low during the process, or you'll just inject air back into the lines.

 

Pop the wheel, pull the drum and take a look see. If the rubber cups on the ends of the cyl are wet the seals are gone.


If you are going to replace a rear cyl I recommend a couple of things

First - you may as well order the stuff to do both sides. If one side went bad you gotta figure the other is not far behind.....

2. There is a rebuild kit for the wheel cyl's but the cyl isn't that expensive on its own. I bought new and kept the old and will rebuild for spares one of these days. GWC1102 came with the gasket and the clip - which I wish I'd know cuz I ordered those alone to replace and ended up with spares . . .
If you take an old apart you'll see that the rebuild is easy however.

3. If you are stock in the rear then from the cyl you have a short copper line from the cyl that then joins a rubber section. When I tried to get the copper section apart from the cyl it was a no go so either take this apart b4 you order or just bite the bullet and order the copper "stinger" as I call it up front and replace that too. part 115-187 $12.75 usually. Then of course having gone this far you might want to back up all the way to the hard line with a flex stainless.....


#44 above



[yes YOU get to bend that 'stinger' to shape SO work SLOWLY as you do NOT want to kink it {throw away and start over} & keep the bend away from the connectors or risk a leak....]

4. When time to get the clips back on just press the whole thing with a set of channel locks.

5. While in there you will certainly be taking a look at the shoes and it is a good time to think about replacing those. I found the springs to be rusted and went ahead and replaced those too 185-665 and 115-143. And of course a great time to wire brush everything and hit with some phosphoric acid to kill rust and a heat resis' paint. You can do it on the car but bench is easier. Get those adjusters all freed up too.



Sounds like a lot but actually pretty straight forward. Couple of hours other than waiting for paint to dry.

I use one of little hand vac' gizmos (mighty vac - harbor freight has it) and find bleeding to be a piece of cake. You won't have trouble opening the valve on a new cyl and that should be the only one you need to mess with.
http://www.northerntool.com/shop/too...4&ci_sku=33160

Do you have a problem at the master cyl???? I think this is a totally sep' issue and unless you find signs of leakage there I'd not mess with it. Where to look???? Where do you put in brake fluid? Look at the underside of that . . .

p.s. don't forget not all classics have disks up front . . . That was one of the big improvements Coooper S bought into the game was it not?

 

Heck... I may just try this on my own after all...

Questions:

1. So I'll need to replace a part between the hard brake line and the cylinder? It looks like the hard line clips right onto the cylinder, looking at it from the outside (have not dis-assembled yet).

2. I plan to order complete cylinders (X2) and just replace both - GBCarparts has them for $28 apiece. From the picture, it looks like the new cylinder has all the seals and everything I need (yes?)

3. I do have an assistant, but a bleed kit sounds like a good idea - has anyone used one they'd specifically recommend? I understand the basic theory (the bleed end is submerged in clean fluid, the reservoir end should remain topped-up in order top not send air down from the top end, pump to squirt old fluid + air bubbles down into the lower pool of fluid), but I've never actually *done* it.

4. Mighty-vac? How does that help?

Thanks guys!!

 

Wheels/axles move up and down in relation to the car body, whether on shocks and springs or cones or whatever, so the brake line connection cannot be only hard line. Yes, a hard line connects into the wheel cylinder, and Capt seems to indicate its a PITA to remove, but there is also some sort of flexible line connecting that short hard line to the larger hard line coming from the master cylinder.

 

Looking at Capt. BJ's picture, I think what I'm seeing coming out of the back of the wheel is #44, which (if I'm reading it right) goes into #43, which should be the flex-line you're talking about.

 

on the stock set up

from the cyl you go to a copper line that threads things to the inside of the suspesion arm and then connects to a rubber flex line which is hard connected at that point. Rubber part is # 43.

I broke the copper line at the cyl but had better access to get a clean disconnect at the 43/44 connection. Given the hand bending nature of 44 I'd plan to replace them but you might be able to re-use. All I had to do was wait a few days for the additional parts plus pay an additional shipping charge after I found I needed them..... Get 'em in one box and save the shipping . . .

If you are a non-rubber brake line fan you want to replace 43 .... I suppose one line could replace 43 AND 44 but there would be some serious chafe points.

So I'll need to replace a part between the hard brake line and the cylinder? It looks like the hard line clips right onto the cylinder, looking at it from the outside (have not dis-assembled yet).

That's where I could not get things apart and the next connection up has better access . . I'm just providing a warning and look out for based on my experience

and Capt seems to indicate its a PITA to remove,

mine was a pita to remove because of corrosion and limited access. trying to get it free I snapped the line b4 I got things apart. Next connection up the line is in clear view and maybe you would see the line twisting b4 it snapped as it did 4 me. I had a successful disconnect there...

ABSOLUTELY this is not THE WAY

it is what happened to me . . .

 

I was just planning on ordering 43 and 44 for both sides...

 

if you do that you replace everything back up to the hard line and should be good for a serious bleeding

 

I just went through my classic Mini and replaced the entire front brake system, master cylinder, hard copper lines from the master cylinder, both rear wheel cylinders and the hard and soft lines from the rear wheel cylinders to the subframe. Here's my thoughts:

1) As suggested earlier, replace both rear wheel cylinders at the same time. You'll find that they are probably the most inexpensive parts for the classic that you'll ever buy. Also, you need to make sure that you get the correct size, as the size affects the amount of brake pressure applied by the pedal.

2) rear wheel cylinder hard lines - is your classic lowered? Jack @ Seven Enterprises helped me a great deal when I was fixing my rear brakes. Turns out they have a solution for lowered Minis that replaces the brake line (both hard and soft lines from wheel cylinder to subframe) with stainless steel braided lines. The soft rubber lines break down over time and limit the fluid flow to the rear wheel cylinders. Also the hard copper line fittings get damaged easily. You might want to consider this option. I can elaborate if you want ...

3) Not sure what master cylinder you have, but I had an early split system on my '73 and the master cylinder is no longer available. Also the rebuild kit for my master cylinder is worthless since the master cylinder wall was worn down and the rebuild kit doesn't address this issue. My only real solution was to buy a later model split system master cylinder, but it had different line fitting sizes so I also had to replace the hard lines that connect to the master cylinder. Soooo, don't do anything with the master cylinder until it fails, which it likely hasn't at this point.

4) bleeding systems - I have a good quality metal Mity Vac and it works ok. not great but ok. For about the same amount of money I bought a Motive Products Power Bleeder from summitracing.com with the 45mm cap (your master cylinder might have a different size cap). It is 'the' solution for brake bleeding. It's basically a container that contains new brake fluid and a fitting that threads to the master cylinder in place of the cap. You pressurize the container, then crack open a bleed screw and the pressurized fluid is pushed through the system. No pedal pumping. It's truly a simple single person bleeding solution. The added benefit of this is that you can put all new fluid in the system, getting rid of all the old dirty fluid.

Hope it helps,
Jeff

 

replace 43 and 44 keeps it fairly original

or replace both with a single braided line as Seven suggests.

Braided is assumed to be stronger and prefered from a race stand point and certainly you won't have to worry about messing up when bending the copper stinger lines....

I have not compared from a $$ angle but you might want to do that.

 

I haven't seen braided lines that replace both the flexible hose and the hard lines. Typically the hard line will always be there. Would be a lot of bends/angles to run just a flexible line.

I wouldn't worry too much about replacing the hard lines, but changing the flexible lines isn't a bad idea.....as long as you are in there.

 

Isn't that what was just described?

Turns out they have a solution for lowered Minis that replaces the brake line (both hard and soft lines from wheel cylinder to subframe) with stainless steel braided lines.

 

Ok, so they do have them, but it seems like an unnecessary fix to a problem he doesn't already have.
"Designed for radically lowered Minis to avoid the rear metal brake pipes being crushed" - Keyword being radically.

 

ok ok

what I don't know is if

the copper stinger and the rubber connector

is less expensive then a

stainless relplacement of both . . .

 

My car is *not* lowered (beyond the typical amount caused by old rubber cones, of course). One day I'll probably swap the cones for springs and put in a Hi-Lo system, but that's for later on.

Re: Might Vac: Is this the one people use? This one is about $100 cheaper than the one I'm finding on Summit Racing's site (maybe I'm looking at the wring item?):

http://www.harborfreight.com/mityvac...ump-39522.html

This seems pretty reasonable @$40 (if it actually works). I'm assuming this clips to the line near the rear wheel cylinder and pulls fluid *from* the master reservoir? Also, will all 4 lines (front/back) need to be bled 1,2,3,4?

Re: Master Cylinder: My car is actually a 1992 with the single reservoir, and I have to assume that it's the original part that's never been serviced/repaired/replaced. Can I visually confirm that it's OK (leaks, other damage/corrosion)?

 

Yes, that is the MityVac I was referring to, except I have the metal one ... I find plastic tools just don't last in my garage . The MityVac connects directly to the wheel cylinder bleed nipple.

Bleed Procedure is:
1. fill master cylinder,
2. connect MityVac to wheel cylinder
3. pump MityVac to produce a decent vacuum (I usually get into the top 1/3 of the dial)
4. crack open bleed nipple to allow vacuum to suck fluid and air from line.
5. close bleed nipple when vacuum reaches about 5 psi
6. repeat steps 3-5 over and over and over and over until your forearm no longer works. Fill master cylinder as needed.
7. check pedal pressure and let forearm recover

If your fluid level was low enough for you to notice it in the pedal, then you've pushed air into the brake lines at the master cylinder, which means you really should bleed all four corners. Start with the rears since you'll lose most of the fluid from those lines when you replace the wheel cylinders. You'll know straight away if the front lines have air because the pedal will be very squishy.

The biggest give-away that the master cylinder doesn't work is if the pedal no longer produces line pressure. Using the standard 2-person brake bleeding procedure (one at the pedal, one at the bleed nipple) you'll find that pumping the pedal won't produce any pressure. Another tell tale sign is if you start getting fluid dripping down the pedal assembly (because the seal has failed).

Good luck,
Jeff

 

It was making great pedal pressure until I lost the rear wheel cylinder, so I'm going to assume the master is OK.

Thanks for clarifying the procedure!