Problem bleeding master cylinder

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david meyers
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Problem bleeding master cylinder

#1 Post by david meyers »

Greetings , while treating my 64C to new Koni's, a fresh gallon of Swepco to the tranny, lots of needed grease to the front end...decided it was the perfect time for a needed brake flush, (not that the brakes felt bad)
starting RR/LR/RF/and LF , it got progressively dirtier , but all air and color cleared up after a liter was used ( I was using a Motive/pump up /Power bleeder/bottle) ...as I was trying to get the LF totally clear, I guess the
bottle connected to the reservoir was tilted a little... to where the pick up tube was sucking a bunch of air, and the reservoir looked pretty much empty, but I filled it up , and being anxious to they the shock, etc
put tires on/ off the jack stands, only to find after starting and driving down my street ...no brakes, tried pumping nothing , turned around , and in 1st gear limped home slowly <sigh>
So back up on jack stands/wheels off , another bottle of brake fluid, bled all nipples ( except front two inners on calipers where stuck , and I didn't want to break one off ) ....still zero pedal pressure <bigger sigh>

So I suspected the master cylinder, and tried to find something on our forum archives about bleeding/master cylinder problems/fixes/procedures,etc ...nothing of help as usual when I've searched for info the last few years
when our website was "improved" changed/fixed , ( if anyone can find / forward a link , please post, thanks) but I went on a google search , and watch a guy bleeding his Ford master cylinder (on the car) by running a line/tube from
L/F nipple to reservoir , pumping brake a bunch , and eventually the fluid , and air would make it's way out and up to the reservoir ,/ get rid of the air/ and start a complete "cleaning cycle"...worked for him, but not me

So after my wife crawled out of the car ,after pumping for a half hour and a lot of words I can't repeat here, , still no pedal pressure....hook up the power bleeder , got a bunch of nasty funk out of the bleed valve , still no pressure on
pedal...then as I pumped up the pressure on p/b bottle and was twisting /repositioning it , the damn tubing broke, and sprayed a bunch of fluid around battery box...luckily don't think on any paint that I could see <more 4 letter words> after cleaning up that mess best I could I got to looking at the master cylinder again , and noticed the metal line leaving M/C to R/F caliper is on top of M/C .hmmm should I be trying to get the air out using that valve ?

sooo, that's where I am now , any ideas/suggestions....please help if you can ...before I (slip on more break fluid, again) "And have fallen and can't get up"
thanks,
dm
David Meyers

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David Jones
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Re: Problem bleeding master cylinder

#2 Post by David Jones »

David, first question, do you have a dual circuit master cylinder? If so they are notoriously difficult to bleed. As you have noted you must bleed all the caliper halves, the two you missed may be causing the problem. Also the disc brake system is more difficult to bleed than the drum brakes but it usually results in a spongy pedal until you bleed the brakes after a few days of driving. Apply a little heat to the stuck nipples and also maybe a few light taps with a hammer as you apply pressure with preferably a ring/box wrench. The disc brake nipples are more substantial than the drum brake ones and will take more effort to break off.
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Dan Epperly
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Re: Problem bleeding master cylinder

#3 Post by Dan Epperly »

If you have a dual circuit you must bleed the fronts first then the rears. Then there is a little valve on some at the top of the reservoir that you must open and bleed.

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Re: Problem bleeding master cylinder

#4 Post by Doug McDonnell »

David Before you do anything else make sure that you have 1mm of free space between actuating rod and pedal. You can sort of bleed the Master cylinder by loosening the brake switch. I have never had good luck with pressure bleeders unless pressure is very low. Too High a pressure doesn't help. Air bubbles go to low pressure so when you open bleeder valves you want very minimal opening. Brake fluid "shooting out" doesn't allow the air bubbles to be evacuated. I first Gravity bleed followed by the 2 person pumping method. And YES you will need to bleed again after driving for a while to get a firmer pedal.
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david meyers
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Re: Problem bleeding master cylinder

#5 Post by david meyers »

Thanks guys, appreciate the feedback... yes I do have a dual circuit unit, and with a friend helping yesterday I tried a lot of those things, and will do more
We came to the conclusion that I probably "toasted" the old master cylinder by too much repeated full pedal movement/pumping , and I did get debris sucking from bottom of M/C
via nipple on R/F...we used his power bleeder did fronts first , and I had already done rears first twice before...we tried bleeding using brake pedal ...no pressure /minimal
Gonna have to pronounce the M/C dead I guess ...my tired old back, and body is giving out , from too much bending/ stretching /crawling <sigh>

Guess I'll order a new M/C today from one of our vendors, along with some new nipples ,and other items, in hopes of getting her back on the road by next weekend for an annual 356 NW group gathering
if my luck and efforts don't change by then I can always take the 911 and park off in the corner, I'm sure there will be lots of good 356s to drool over , and stories of problems/things like this

...I'll report back as to how it goes
thanks again
dm
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David Baugh
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Re: Problem bleeding master cylinder

#6 Post by David Baugh »

A few years ago, I spent an hour unsuccessfully trying to bleed my brakes with my wife pumping the pedal. Finally, I looked inside, and found that she was pumping the clutch pedal. Hmmm ....

Dave
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david meyers
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Re: Problem bleeding master cylinder

#7 Post by david meyers »

I feel your pain Dave...after recruiting my wife to help , I could see she had her doubts ( as did I). She sat in the car staring at the pedals with a kinda "deer in the headlights" look.

"Now which pedal do I push ?" she says ...The one in the middle honey ,I replied <sigh> ...hey at least I don't have to worry about her driving one of my 3 pedal cars eh?

suppose maybe our wives were sisters , separated at birth ?

cheers,
dm
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cory cotherman
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Re: Problem bleeding master cylinder

#8 Post by cory cotherman »

Dan Epperly wrote:If you have a dual circuit you must bleed the fronts first then the rears. Then there is a little valve on some at the top of the reservoir that you must open and bleed.


Is it a valve? or a little bolt with a copper crush washer on the top of the master between the inlet ports for the reservoir? asking because i'm having the same problem. fronts bleed fine but rears wont.

cory

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Re: Problem bleeding master cylinder

#9 Post by Dan Epperly »

cory cotherman wrote:
Dan Epperly wrote:If you have a dual circuit you must bleed the fronts first then the rears. Then there is a little valve on some at the top of the reservoir that you must open and bleed.


Is it a valve? or a little bolt with a copper crush washer on the top of the master between the inlet ports for the reservoir? asking because i'm having the same problem. fronts bleed fine but rears wont.

cory
Yes a small bolt tween the two inlets for the fluid. Just crack it open a bit and have someone apply pressure to the brake pedal very lightly till fluid comes out and then tighten it, should be done.

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Re: Problem bleeding master cylinder

#10 Post by David Baugh »

Do not remove that bolt, unless you're planning on disassembling the master cylinder. It's a pin that restricts the return travel of the forward piston.
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Re: Problem bleeding master cylinder

#11 Post by Martin Benade »

It is not meant as a bleeder, but bleeding there (without removal) wouldn't cause a problem.
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Re: Problem bleeding master cylinder

#12 Post by David Baugh »

Just a warning shot for those who are unfamiliar with the construction of the device, Martin. The forward piston can be destroyed by removing that bolt, then trying to screw it back in after the forward piston has been pushed rearward by its return spring, past the pin location. But, as you've mentioned, bleeding at that bolt does work, as long as one is aware of the potential hazard.

Incidentally, I've had a lot of success with simply filling the reservoir and letting the car set for a few days. The master cylinder will frequently "gravity-bleed" itself enough to continue the process.

Dave
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Re: Problem bleeding master cylinder

#13 Post by Martin Bruechle »

It is important the the person pumping the pedal pumps at a steady slow to med pace, not fast.
Fast or speed pumping can make air bubbles or foam. I always use a clear piece of tubing on the nipple into
a clear bottle so you can see the air bubbles and dirty fluid. With the hose going into a bottle you won't get air sucking back in.

Even on duals I always start on the right rear, then left rear then passenger front and drivers front last.
Put a few miles on it then a final re-bleed. Pump 3 times, hold brakes, crack the bleeder, pedal on floor,
close nipple immediately maybe 2-3 times per bleeder nipple to insure no air is present.

david meyers
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Re: Problem bleeding master cylinder

#14 Post by david meyers »

Well I finally got brakes back, at the 11th hour<big sigh> just in time to go to the NW Bullsession ,yippee

I tried every suggestion/ tip/procedure that ya'll suggested, and more,
but even after running probably a gallon of fluid throughout the system last week
( with new M/C ), I could never/ever could get any pedal pressure, then about the time I was looking for a sharp object to fall on
another friend came by and suggested a variation that had worked for him with the Motive power/pressure bleeder

We pumped up the pressure to at least 15-20+ psi, ( had been running 5-10) then instead of just cracking the bleeder nipples
a half turn like I had been doing, he opens them way up to over 2 full turns to hopefully blow it out ...bingo ...got all the rears to burp ,
pedal started to get some pressure , then did the front 4 valves , and even better feel on the pedal. Stops well , but since
I was sure to leave a little more clearance between M/C rod and piston I have to push a little further/more travel on the pedal to get brakes
but I put about 250 miles on it yesterday , and maybe after burning another tank of gas , I may bleed again..
.then again I may wait a little longer <smile>

thanks again guys for the help !
dm
David Meyers

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