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 Posted: May 3, 2018 03:35AM
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Quote:
Originally Posted by Dan Moffet
The fluid level was down a little so I added more but still could not get any pedal pressure at all

Does this sound like it has ingested air or has something untoward happened to the master cylinder? There are no leaks apparent anywhere so far.
If at the start the reservoir was relatively full, then the pedal sinking to the floor with little to no resistance suggests failed seals in the master cylinder.  

Doug L.
 Posted: May 2, 2018 01:01PM
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CA
Thanks for all the ideas. The story so far:

When waking up the Mini, I found the brake pedal lower than I remember it from last year. The handbrake also barely held. So (to me) the logical step was to adjust the rear brakes (it has 8.4 disks at front). The right rear adjuster turned like it was brand new but did come up to providing light drag. The left rear would move stiffly so I gave it some WD40 and some time. It loosened up and also adjusted to provide drag. I will be adjusting the handbrake tomorrow.

The master cylinder is the yellow-band type and there was fluid in the cone-shaped part of the reservoir. When I got in the car to test pedal height, it went to the floor with no resistance... repeatedly. The fluid level was down a little so I added more but still could not get any pedal pressure at all. I left it sitting with a full reservoir while WD40 does its work on the bleeders.

Does this sound like it has ingested air or has something untoward happened to the master cylinder? There are no leaks apparent anywhere so far.

.

"Hang on a minute lads....I've got a great idea."

 Posted: Apr 29, 2018 11:59AM
 Edited:  Apr 29, 2018 08:00PM
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There is another 1-person method that I've used with success—it's a favorite of vintage restoration shops. You simply open the bleed valves one at a time (in the correct sequence, of course) and using clear tubing, let the fluid drain into a container by gravity alone. No pumping the brake peddle, no additional pressure or vacuum necessary and no chance of sucking air into the system. Once a sufficient amount of fluid has drained into the container, close the valve and move on to the next wheel.

The reason it's popular with resto shops is that older master brake cylinders have had their bores polished smooth from years of use and often have "steps," irregularities and even rust in the bore beyond the normal travel cycle of the master brake cylinder piston. Pumping the brakes during the 2-person bleeding process sends the piston into this uncharted territory where it encounters these rough spots and can damage the piston and/or o-rings. This might be an expensive mistake on an 80 year old Bentley or Jag.

The disadvantage of this method is that it takes a looong time, up to 1/2 hour per wheel. Another drawback is if there are any restrictions in the brake tubing or brake cylinders, the relativity low pressure involved (about 1.5 psi) won't be sufficient to provide a decent flow and therefore may not flush out trapped air that can be lurking in the system. On the other hand, I'd want to know if my tubing had restrictive kinks or my brake cylinders were gummed up and causing restriction.

 

Michael, Santa Barbara, CA

. . . the sled, not the flower

      Poser MotorSports

 Posted: Apr 29, 2018 05:08AM
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As with many things there are as many ways as people doing it. I have always done mine the same way. I keep rolls of PVC tubing and a tube of brake grease. Standard approach after rebuilding calipers with SS pistons and kits, replacing rear wheel cyls., adjusters, springs, shoes (use the good ones Mintex) and drums. Also hoses at all four corners and replacing any or all hard pipe in question, master and booster if fitted. Up on the tall jack stands wheels off, grease the threads on the bleeders followed by tubing. I use plastic water bottles with a hole poked in side for the tube. I open all four at one time fill the master and hope gravity will do the hard work. While I have never been one for bench bleeding the master I do bleed the master first when the pumping begins. Cracking the fitting until fluid appears around the threads. Yes I have read and heard you start her or there. I start closest to the master and work my way out. Fronts are easy most of the time. The rears are almost always an issue. I work with a helper as soon as I can find one. We do three gentle pumps and hold. I say gentle as quick sharp pumps mess with the bias valve and on later ones the shuttle valve. Once I have clear fluid all around with no bubbles I seal the system replace wheels and drive a day or two. Before delivering I put her back in the air and run though all four corners again, adjust the rears and let them go. Yes, I have two easy bleed kits and a pump. Having started with a 1930 Model A Ford with mechanical brakes followed by mini single leading shoe brakes I know what it is to have questionable brakes. I have noticed when people ride with me they tend to go for that brake pedal on their side before I look for mine. The last couple of minis I have bought have been 1275 power drum brakes that failed to stop in time. Be safe and do the best brake job possible, how ever you bleed them. Steve (CTR)  

 Posted: Apr 28, 2018 05:34PM
jeg
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EZ-Bleed for me, also.

The peasants are revolting...          

"Gone with the Wind" - a brief yet moving vignette concerning lactose intolerance

 Posted: Apr 26, 2018 03:29PM
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With all due respect Dan I have been using the EZ bleed 4 years you attach it to your spare tire valve stem put some fluid in it attach it to the brake master cylinder go around open the lead screws on each wheel and the liquid just pours out easy.

 Posted: Apr 26, 2018 03:03PM
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don't jack up one end of the car.  If you jack it up, put both ends up so wheels are level.

Don't pump it up and then crack the bleeders.  Crack them open, press slowly to floor, assistant closes bleeders, slowly raise pedal. I have no assistant, I have a hammer just the right length, it jams between pedal and steering column bracket.

Trick...sometimes, this works on all four.  Crack the bleeders.  Take off the mcyl cap and fill with fluid.  Go back in the house and have a sandwich.  Back to car, top up mcyl, close the bleeders.  All of your nipples should be dripping or on the hairy edge of wetness.  (If I see that on a t-shirt I want royalties.) Do a final bleed, driest wheel first.

 Posted: Apr 26, 2018 02:35PM
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I prefer the two person, clear tube, glass jar method. I even have the wife trained for the pedal. I like to watch. 

 Posted: Apr 26, 2018 12:35PM
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If you use the vacuum bleeder, remember that you will get best results by coating the nipple threads with something to prevent air from being sucked in along the threads.  The Speed Bleeders have some type of goo on their threads to seal against air.  In spite of being brakes... you can use grease on the nipple threads.  The grease is not going to get sucked in where the seals are.  Teflon tape is another option.

There are at least two 2-person methods of bleeding.  The one I've seen a lot of guys do is to have one guy in the car who pumps madly to build up pressure then holds the pedal down while the second guy cracks the bleed nipple open.  I don't use that method. 

The method I use is sometimes called the flush method.  One guy under the car cracks the bleed nipple open and calls to the second guy to slowly push the pedal down.  At the end of stroke the guy in the car calls "down" to the first guy who closes the bleed nipple and calls back "release".  The cycle repeats itself until clear liquid without bubbles is seen in the clear tube.  You can generally get by with only one person doing this method if you have a tube with a check valve inline OR if you buy Speed Bleeders.  

If you have let air in the system you may find the pump-pump-pump-release method does not allow you to bleed the rear brakes because it spools the proportioning valve to the closed position.

Doug L.
 Posted: Apr 26, 2018 12:14PM
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CA
The 'small suction pump' I have is actually intended for brake bleeding and vacuum system analysis. It has clear plastic tubing and an enclosed/sealed receiving jar. The pump draws air from the jar, which in turn sucks on the tube to be attached to the bleeder nipple.
It has been over 45 years since I have bled brakes on a Mini (not the same car!), but I do recall that with a 2-person method, the bleeder should be opened while under brake pressure and closed before the pedal guy lifts off for the next stroke. I do see however that if the bleeding tube's free end is kept immersed, it is unlikely to draw air back in, unless the bleeder is opened too far and air gets past its threads.

Calipers are on the right way!

Not sure I want video running while I'm "in the car pumping away".....

PS. I managed to get the garage tidied up after winter to get to the Mini. Hope to wake her from her hibernation tomorrow or Saturday.

.

"Hang on a minute lads....I've got a great idea."

 Posted: Apr 26, 2018 11:39AM
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I'm not a fan of any method where the tube is just resting in a jar and no one is opening and closing the bleed nipple.  But... to each his own.

If you cannot find a second person, you can make a bleed hose with a check valve in it or you can go to the local parts store and buy sets of Speed Bleeder bleed nipples.  

Doug L.
 Posted: Apr 26, 2018 09:54AM
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I'd recommend using a clear 3/8" rubber line and attaching to the bleed screw. Run that rubber line into a clear 500 mL pop bottle and pour a slight amount of the brake fluid in the bottom of the pop bottle. open the bleed screw, and start pumping the brake pedal. I found that after ~20 strokes I had clear fluid to the back, and maybe after 7 I had clear to the front. Add a few extras to make sure. 

You dont really need a vacuum / pressure pot or any special equipment to do this, dont even need a 2nd person. Just make sure that after every 10 strokes you refill the reservoir - religiously - or you will end up doing the entire process over again like I did. 

As you are doing this likely solo, set up your cellphone to take a video of the bleed hose while you are in the car pumping away. Watch the replay. This way you will know if there are still bubbles in the system. Also make sure that your bleed valve is located at the top of the disc brakes. If it is at the bottom, you have your disc brake calipers installed on the wrong side of the car, and no matter what you do, you will never get them bled properly. 

 Posted: Apr 26, 2018 08:19AM
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Dan,  as mentioned above, if you already have fluid in the car and hit hasn't dried up or dripped out, stick with whatever is in there (presumably DOT-3 or DOT-4).  Since you are flushing, you won't have any problems bleeding the brakes as long as you keep topping up the reservoir as you go from corner to corner.

Doug L.
 Posted: Apr 26, 2018 07:40AM
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Sir dan ! !  Ha!
 

A quick and easy flush wont use more than a quart of brake fluid. ( only touch points will be the  bleed ports. if system is in good condition)


Dot 4 is Hydroscopic (absorbs moisture) is why is reccomended to replace the fluid annually.
  Dot 5 - Silicone = whole conversion required. some seals will not like it could cause issues. best installed with NEW componets. Has  its plus's and minus's

In my opinion /  Experience . since the Dot 4 is hydroscopic. the moisture collects no matter what we do. here in the south east USA .. I rarely see rear wheel cylnders lasting more than 2 - 3  years on a 'rarely driven car '  they either rust up solid and will not move. or rust internally = move = slit the seals then leak.

 Before you start bleeding I would pull the drums and simply shake the pistons in the cylnder. make sure they are free.
  If they are 'hard to move. or not move = you should Cylnder rebuild  / or  replacement before ANY brake fluid changes.

 Go ahead and bleed the clutch system too.

 Posted: Apr 26, 2018 06:25AM
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The Mini is circa 1986 with stock 8.4" disks and rear drums, with a dual master cylinder (no servo involved). The car was built for export to Germany if that makes much difference. I believe it is a front-rear split system - I will confirm when I get the car out of storage. I will inspect all lines, hoses and fittings before starting.

I have read recommendations here that the brake fluid should be replaced about every 4 years. If so, it is long overdue.

Q1: How much brake fluid should I buy to fully flush and fill the system?

Q2: Since nothing is leaking I want to avoid disconnecting any fittings - is this feasible?

Q3: Any tips/tricks? I will be using a small hand suction pump to bleed.

.

"Hang on a minute lads....I've got a great idea."

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