NEVERL8

No good deed goes unpunished. I just got through replacing my rubber brake hoses to the wheels. Figured I would bleed the brakes this weekend, put the wheels on and get it off the jackstands. Last year I rebuilt all the calipers and pressure bled the system successfully. For some reason this time I cannot get a brake pedal. Stymied I went onto the forum and did a seach on brake bleeding. I read everything about "bench bleeding" and using the Motive POS pressure bleeder (which I have). 8 hours and 3 quarts of brake fluid later still no pedal.

I did a "bench bleed" with the MC still on the car. How you prevent air from getting back into the MC when you disconnect the bleed tubes and before you hook up the hard lines is a mystery to me. I screwed in plastic threaded barb connectors into each port and ran tubes into the reservoir. It was a messy process. I did not realize the front brake tube on the MC is a 20 pitch thread and the rear brake tube is an 18 until I tried to screw in a 1/4 inch threaded barb connection. Needless to say the 18 pitch barb was not too happy with the 20 pitch threads but I managed to managlate it and get it in.

After careful cycling on the master cylinder all air bubbles were removed. I then reconnected the hard lines as quick as possible. As I said before, how you prevent air from getting back in to the master cylinder during this process remains a mystery.

I hooked up the Motive bleeder, using a 6 inch C clamp to hold the top plate in place. Cranked it up to 15 PSI and no leaks. I then put it up to 20 PSI and again no leaks. I then proceeded to push almost 30 oz of fluid through the system. During the bleeding process I tapped on each caliper with a rubber mallet. I made three complete rounds around the car. Nothing but fluid coming out of the calipers. Life was good. The brake pedal felt good.

I relieved the pressure on the Motive bleeder (slowly) and reinstalled the MC cover, no break pedal. Thinking I had done something wrong I completely redid the motive bleeding process again, another 30 oz of brake fluid. With the MC pressurized by the Motive bleeder I had a brake pedal I could live with. I then VERY slowy removed the pressure from the system over a period of 5 minutes. Same result, no brake pedal.

At this point I have spent the weekend trying to bleed the brakes, used all the advice and ideas on the forum, and still have no brakes. I am out of ideas short of taking out the MC and tearing it apart. Since it was working perfectly before this little journey rebuilding the MC would not make sense and I would only do it out of frustration.

Is bench bleeding on the car OK? I assume you slowly cycle the MC until no air is present. This is what I did. Will removing the bench bleeders and attaching the hard lines introduce air back into the MC? Seems like it does and there is no way to prevent it. Pressurizing the MC with the Motive makes the brake pedal firm, removing the pressure and the pedal goes to the floor.

It seams like I still have air in the MC, there is no air coming out of calipers even at 20 psi on the Motve.

I am stuck.

devildog

Bruce,

I just went thru a similar torture on the 66. New brake lines, new wheel calipers, rebuilt master, tested and tested, even had the master sleeved with SS and honed.

Ran much brake fluid thru it with power bleeder, pump by foot, dripped bleed, etc.

Pedal would go to floor!

Removed the silicone fluid and washed out system with alcohol, replace with DOT fluid.

Works perfect. It seems that the silicone entraps air bubbles in the smaller lines on a C-2.

May not be your problem, but post this for others as well.

Joe

AZDoug

ALL lines MUST be connected to bleed the brakes.

Look for the bleeder screw on each caliper.

Attach a clear bleeder drain hose to the furthest caliper, have helper pump pedel 5-10 times, and hold pedal to floor. Open bleeder screw until helper foot on brake pedal hits floor. KEEP PEDAL ON FLOOR.

Close bleeder screw.

Pump pedal as above,and Repeat 5-6 times until no air bubbles are seen in clear bleeder drain tube.

Move to second farthest wheel cylinder/caliper.

repeat as above, then next two calipers and repeata s above.

Doug

Plan B

Why would you bench bleed the master if you were just replacing brake hoses? Did the master run dry when you removed the hoses? After going through all that fliud and still no pedal, I'm taking a guess by bleeding the master that has been on the car for a while and by bottoming out the master cylinder piston, the seals ran over some gunk in the bore where it's not use to travelling and ruined the seals. Sounds like the master is bad.

Thanks,
b

65 vette dude

I would try to bleed it the old fashion way, with a helper on the pedal,and see if you can get a pedal that way. If not,I would look at the M/C.

w1ctc

One last thing to try that worked for me (done as a last try before pulling the MC). Repeatedly pump the brakes for about 15 minutes. Been 2 years and all is still good.

DansYellow66

I don't have a Motive bleeder so I can't speak for it - it should work from what I know of it. But the old helper depressing the brake pedal while bleeding the line is what I have always had to resort to. My wife has become quite practiced at this over the years. I don't have to tell her what to do anymore. Also don't mess with the vacuum pump bleeders as I've had too much trouble with bleeder screws leaking at the caliper while trying to evacuate fluid and air from the line.

I'm not clear at the lines and fittings problem you ran into but it sounds like you might have a cross threaded or mis-threaded fitting. Are you sure you have a good seal at the master cylinder?

NEVERL8

The rear cylinder reservoir ran out of fluid while the LR caliper was off the car. Looking back I should not have let this happen. The front cylinder reservoir did not.

I "bench bled" the MC out of desparation since nothing else was working.

I did methodically bleed the brakes using both conventional and Motive method, starting with RR, LR, RF. LF. I did this several times. Usually you can pump up the brakes, hold and bleed. The brakes do not hold enough pressure to pump them up. There are no leaks in the system. I confirmed this by pressurizing the MC to 20 psi and holding it there for 30 minutes.

Maybe I hurt the seals in the MC by pushing the brake pedal to the floor repeatedly. Still with the MC pressurized to 15 psi with the Motive bleeder, there is a fairly good brake pedal so I do not think the internal seals in the MC are compromised.

Each caliper was tapped with a rubber mallet while bleeding to dislodge any air bubbles.

nassau66427

I believe the recommended sequence for bleeding the brakes is: left rear inner, left rear outer, right rear inner, right rear outer, left front and right front.

You might want to give that a try. Don't let the MC go dry or you get to start all over again.

skids

This probably doesn't apply in your situation, but I just went through the same ordeal on my Grand Cherokee. New calipers, MC, rotors, etc. Bled MC thoroughly, all calipers thoroughly, no bubbles at all. No brake pedal. Well, oops. Had the front left caliper on the right side, and right side on the left. Everything fit perfectly,except now the bleeders are on the bottom of the caliper instead of the top where they belong. Switched them around, rebleed, and now excellent pedal.

NEVERL8

I may try the alcohol trick even though I am not using silicone brake fluid. Nothing else seems to be working. I remember using this on a car in the distant past and it worked. Thanks for jogging my memory.

Tampa Jerry

Sounds like you dislodged the seal on the master cylinder. It is a good idea to place a 3/4" block under the brake pedal while pumping the brakes. The piston can be pushed passed its limit. I would rebuild the M/C. The kit is inexpensive. Next bench bleed the M/C. Bleed the system as noted above. Jerry

NEVERL8

Jerry,

When I pressurize the MC with the Motive the pedal is quite firm. I pushed and held the brake pedal with the MC pressurized and the pedal did not move at all. It did not slowly sink to the floor as I would expect if the MC seal was compromised. Am I wrong thinking this is a good test for the MC seal integrity? I do not understand why the brake pedal is firm with the MC pressurized above 10 psi and then goes to the floor once I remove the pressurization.

NEVERL8

I am done. Just totally purged the system with alcohol, then refilled and purged with DOT3 at 20 psi. Absolutely no air coming out of the system. Same results. Very nice firm pedal with the Motive pressurizing the MC at 10 psi. No pedal once I remove the pressurization.

Tomorrow the MC will come off and I will take a look see. I am not happy about this.

bobs65

I'll be watching this post closely as I'm about to do the same thing. Today I got the calipers/stainless hoses on, rebuilt the MS with a kit from Keen parts, bench bled the MS and hooked up the lines.

It's sitting right now with the bleeders open while I read the MityVac manual. A buddy of mine and a search of the archives also talked about gravity bleeding? I guess thats what is happening now while I wait.

Bob

Kensmith

I didn't read if you have power brakes. If you have power brakes, you need to start the car so vacuum will let the brake booster diaphragm work or you will never get any pedal. If not power, maybe a bad master or need a new O ring on the piston as sometimes they collapse or get inside-out.

NEVERL8

Please let me know how you bench bleed. Once you disconnect the bleeders how do you get the MC back into the car and hook up the hard lines without a) drooling brake fluid everywhere between the bench and the car (I assume the MC has fluid in it) and b) not getting air in the lines during the transition from the bench to the car.

I am missing something here.

Thanks
Bruce

Kensmith

You need rubber plugs to inset in the openings, you will get some air and you can try to reverse bleed from wheel cylinder back to master. Air will rise so not a problem. If not, you need to go through the old method of bleeding again. Just recycle the old fluid as long as it's clean.

bobs65

I didn't use a standard bench bleeder(a couple hoses etc..), I just plugged the 2 lines with a couple plastic screw in plugs, pumped the piston until it got real hard and no more bubbles, capped it and took it over the car, mounted it back to the booster and then pulled the plastic plugs and put in the steel as fast as I could. Yes I did get some leaking during the exchange, but not much...more on the front side than than the back.

I haven't actually start the entire bleed process yet. Thats next.

Bob

Kensmith

Try bleeding the lines by pumping the pedal. Then start the motor and let it run, pump the pedal and see if you get brakes. The booster has to have some vacuum to work.