Brake Bleeding Problems

[Dennis Detweiler]

I have a Scarebird disc brake conversion on my 39 Plymouth. Stock rear axle with new wheel cylinders and shoes. Adjusted the top and bottom of the shoes to fit close tolerance to the drums (they rub). I just finished installing a Wilwood 8614 dual master cylinder, which has master bleeders on each reservoir to bleed the master. Bled the master to get solid fluid extracting.  I jacked the front higher than the rear, then rear higher than the front to bleed the master to tip any air to the front and rear of the master. Also installed a Wilwood proportioning valve and 2 lb residual front and 10 lb residual rear. I've tried two self bleeding methods (one by using a siphoning cup from Harbor Freight to draw fluid through each bleeder). Tried the old fashioned method of connecting a hose to the bleeder and down into a waste container that has some fluid in the bottom to keep air from retracting backwards. I've run 2 quarts of fluid through the lines after several repetitive tries. I don't get a pedal until the pedal is half way to the floor and then it's spongy. My last attempt will be to have someone work the brake pedal while I open and close each bleeder....another old fashioned method that I've used on my cars with success in my younger days.  

Any input as to why I'm not getting a good solid pedal? It's about to drive me normal.

[Dodgeb4ya]

Bleeders on the calipers at the top?

[Dennis Detweiler]

Yes, bleeders are on the top. No leaks in any of the lines. There must be air trapped somewhere in the  lines? Getting it out seems to be a problem. When I use the old two man method, should I have the person in the car pump it several times before I open the bleeder each time? Maybe that will help?

Edited August 8, 2019 by Dennis Detweiler
more info

[joecoozie]

43 minutes ago, Dennis Detweiler said:

Yes, bleeders are on the top. No leaks in any of the lines. There must be air trapped somewhere in the  lines? Getting it out seems to be a problem. When I use the old two man method, should I have the person in the car pump it several times before I open the bleeder each time? Maybe that will help?

Have the person in the car pump the brakes several times and then hold the pedal down. Open the bleeder and have the person slowly push the pedal to the floor and hold it there. Close the bleeder and repeat the process until there is no air in the line(s). Also, make sure the master cylinder is refilled each time so as not to introduce more air into the lines.

Hope this helps and if I have stated anything you already knew I apologize.

[Plymouthy Adams]

bleed the longest run first and work your way to the shortest...

[Dennis Detweiler]

I've been bleeding the system by the book and the above mentioned methods. The only difference may be to try pumping the pedal up each time. I live alone, so have to recruit a helper.

[50net]

just  my 2 cents worth. on rear drums check your book and see if says back your shoes away from drums while bleeding?

[Dennis Detweiler]

The 1939 shop manual for bleeding the brakes doesn't mention doing anything with the brake adjustments. The information and picture just shows the one man system with a hose and jar setting on the floor.

[soth122003]

Did you check the brake light switch for sucking air or weeping fluid?

 

Joe Lee

[50 coupe]

12 hours ago, Dodgeb4ya said:

Bleeders on the calipers at the top?

I had a helluva time bleading my system after I did the Scarebird on the front (Explorer disc rearend). I had to unbolt the front calipers and turn them to make sure the bleed valve was at the 12 o'clock before I could get the air out.

[YukonJack]

You might want to contact Wilwood or check the instructions for the master cylinder. I have a Wilwood master I haven't installed yet, but I seem to recall they said to remove the residual pressure valve from the master if it's being mounted under floor. About a year ago I replaced my rear wheel cylinders in my 47 Plymouth, it has disc brakes in front and stock master. I went through 3 large bottles of brake fluid trying various methods of bleeding without any success. I pulled the residual pressure valve out of the stock master and started getting a firm pedal after bleeding one wheel. Note: I am using residual pressure valves in the brake lines.  

[Dennis Detweiler]

The Wilwood master has a 10lb residual in the front and rear reservoir outlet and factory ready for drum brakes. I removed the front master residual for my disc brakes and installed a 2 lb Wilwood residual in-line.

I already had a 10 lb Wilwood residual installed in my rear line to the stock rear drum brakes. However, I left the 10 lb residual in the master rear outlet. Would two 10 lb residuals cause air to be trapped? I get good bleed out at the rear bleeders.

[YukonJack]

I can't say for sure. I was getting good flow everywhere too, but no resistance in the pedal until I removed the stock residual valve. You might want to check with Wilwood. 

[Dennis Detweiler]

I contacted Wilwood and the rep said, having two residual valves (one in the master and one in-line) should cause no bleeding problems. So, I'll try bleeding the system by the two man method next week. If it still doesn't get a good pedal, I'll remove the residual in the master to rear reservoir.

[Dennis Detweiler]

I'm stumped!  I've tried every method of bleeding and still can't get a good pedal. It's spongy and goes 3/4 of the way to the floor before I get brakes. I drove it up and down the driveway and applied the brakes and it's not even close to stopping on a dime. Can't lock up the wheels on gravel or in the grass. I did the two man bleed, reverse bleed, vacuum bleed and always started RR, LR, RF and LF. I had two 10 lb residual valves going to the rear drums (one in the master and one in-line and I removed the in-line residual. I have a 2 lb going to the front disc brake conversion. The Master is Wilwood 260-7563 one inch bore and using the remote reservoirs mounted on the firewall. New rear brake shoes and wheel cylinders. Brake shoes are adjusted to rubbing on the drums. Using a Wilwood proportioning valve within 12 inches of the master cylinder. No leaking brake lines.  I followed the bleeding instructions for bleeding the master. It has bleeders on the side for each reservoir with instructions to mount the master and connect the lines before bleeding the master. The master is pumping pure brake fluid after the initial air came out. The front calipers and pads are 83 - 92 chevy S-10 4wd (Scarebird Conversion).  Any ideas? A different master cylinder? Air trapped somewhere?

[DJ194950]

Are your front caliper bleeders pointed straight up or at an angle?? Just a slight bit will leave a small amount of air in the caliper and cause your problem as described. remove one bolt, tip caliper to straight up position, bleed. The bolt is then reinstalled. 

Happened to me so that is why I bring this up.

 

DJ

Edited August 28, 2019 by DJ194950
add line

[White Spyder]

I just changed rear wheel cylinders and have had a hard time bleeding as well. No leaks in the system. Finally gett just a bit of peddle but not like it was before. I didn't have this much trouble when I put disks on the front and replaced all the lines to all wheels. 

 

With the what Little I have I am throwing in the towel and going to get it on the trailer and take it to a brake specialist. 

[dhrandy]

I had replaced all 8 wheel cylinders, all the rubber brake lines, all the brake pads and still had a spongy pedal.  For me it turned out my master cylinder was leaking.   When I replaced that I had to replace the 2 main brake lines.  Now mine is perfect.  But you said you replaced the master cylinder and bench bled it.  With bleeding I started with the back right, then back left.  Next was front right top, front right bottom, then front left top, front left bottom.  I had the wife pumping the brakes.  My self bleeder pump seemed to be sucking in air from somewhere.

[Dennis Detweiler]

The Wilwood master has bleeders built into the pedal (like a wheel cylinder) and directions say to mount it and make line connections before bleeding it. I'm getting pure fluid through the master bleeders now. I get pure fluid at each wheel cylinder after some initial air.

I think the one man system of bleeding with a container on the floor, tubing to the wheel bleeder and some fluid in the container to begin with, allows air to be sucked back into the wheel cylinder by way of the threads of the wheel cylinder bleeder when you release the pedal each time. So, it's not the perfect method, even though the Plymouth manual shows to do it that way. I've never had a problem with the two man method in the 54 years of working on my own cars. I went through the process of two man method twice on this car and end up with the same results. I pumped 3 quarts of fluid through the system trying different methods with the same pedal results.

[Dennis Detweiler]

I'll try loosening the calipers and make sure they're straight up and give that a try.

[kencombs]

Is it possible that you don't have enough master cylinder stroke to actuate all the wheels?  Maybe too much pedal movement(free play) before the plunger starts to move.  Or, maybe the pedal pivot ratio doesn't provide for enough stroke. 

 

Those kind of issue typically arise in a brake system custom fabrication, not a replacement, but still worth looking into.  Maybe try reducing the free play dramatically as a test.

 

Edit to add:  or plug the front and rear ports separately and see if the pedal becomes solid

Edited August 29, 2019 by kencombs

[Lloyd]

I put all new brakes only 39. Granted it was a stock master cylinder but had the same problem.  Looking into the reservoir I saw a small hole I believe was the fill hole for the piston cavity. Noticed that the piston rubber was blocking the hole. I loosened the brake pedal rod adjustment so the piston retracted past the hole and brakes started working. 

[Dennis Detweiler]

Could be my new Wilwood master, but doubt it.

I noticed a screw (plug) at the 12 o'clock position on my disc brake calipers. I've been corresponding with Scarebird today and asked if it's possible that the S-10 calipers have an alternative bleeder position? The current bleeder is at about 11 o'clock position. Rather than removing the caliper and rotating it to make the bleeder at 12 o'clock, maybe I need to switch the plug and bleeder, if that is an option. Or maybe just loosen the plug and let it burp until fluid starts oozing out? I should hear from Scarebird in the morning. Keeping my fingers crossed and hoping this is where the trapped air is located.

[JD luxury liner]

https://youtu.be/ioHjV4d6BWk

might try this type set up.

 

[pflaming]

I was told to bleed the caliper with a lower bleeder valve next to last.