master cylinder bleeding issues

[Materman]

hi all, after I rebuilt and cleaned the master cylinder I cant seem to get it to pressurize up when bench bleeding it, it doesn't seem to have any air in it and it is still soft. do i have to have the entire system installed to get it to pressure up or is something wrong with my master?

Thanks in advance.

[Plymouthy Adams]

bench bleeding involves getting air out of a master in a open line condition..why do you think it should build pressure?

[Materman]

I thought that the pedal should build up pressure when I pump it when bench bleeding like most other master cylinders, or is this different?

[Plymouthy Adams]

_{you are in description combing two operation into one..are you bench bleeding or are you now trying to bleed the brake system..}

[50 coupe]

go to you tube to look up 'bench bleeding' so you have an understanding of what you are trying to do and what the process is. That should help.

[mopar_earl]

If you use the plug the ports method to bench bleed, yes it will firm up. If you use the older method of using hoses to bench bleed, it won't firm up.

Earl

[Don Coatney]

I do recommend you plug the discharge ports in the master cylinder when done bench bleeding to prevent air intrusion and contamination during the install.

 

[Materman]

well, I am trying to bench bleed the master by the hose method, I knew the method for bleeding with plugs and I knew that it would build pressure. but I can't seem to find plugs to fit my master, so the hose kit is all I have and I have never used it before. I watched several videos on youtube on how to bench bleed with the hose method and I assumed that it would firm up like the plug method, but I guess not. not bleeding the system yet, I know now that if it doesn't firm up when I bleed the system I have problems.

[Don Coatney]

The plugs I installed were after I bled the master cylinder. From your comments I don't believe you understand the purpose of doing this job. The purpose of bench bleeding is to remove air from the master cylinder and not to build pressure. Master cylinder bleeding is an open loop. No pressure involved. Once the master cylinder is installed and all of the lines and slave cylinders are installed then the system is closed and only then will you get pressure once all air is removed from this closed loop.

[mopar_earl]

I agree with Don when using the hose method. Also remember not everyone knows of the new method of using plugs instead of the hoses to bench bleed.

The plug method. You install plugs in the master ports, work the master piston at different strokes and the air purges up through the fluid from the internal ports in the bottom of the reservoir. This will cause the piston the be firm as the air purges. Pretty much all new master cylinders come with the plug bleeding kit now. I like it cause its easier and no mess and the plugs can be left in till you connect the lines.

Earl

[Niel Hoback]

I don't believe you need to bleed the master cylinder before you put it on or connect the lines to it. The relief hole in the reservoir allows the air to escape to the reservoir, filling the cylinder. You have to bleed the wheel cylinders last anyway.

Bench bleeding only became necessary when brakes went to dual systems.

[dale]

Darn hard to keep air out while hooking up the lines to the master cyl.  There is a sequence to use when bleeding the system.. I had an awfull time bleeding mine until I let it sit for a few days.  I had a bad new brake cyl. and before I realized it was bad I had gotten air mixed up with the brake fluid so it was kinda milkey looking.  Musta seperated after sitting because when I tried again it was real good.   Must be why they say to press the brake slowly when bleeding the system..  Sequence.. Passinger side rear.....driver side rear.....passenger side lower then upper.....driver side lower then upper.

[Don Coatney]

Your sequence is correct. Furthest from the master first, closest last.

 

Bleeding is much easier if done with a pressure bleeder. Do a Google search on how to make one inexpensively with a garden sprayer.

 

[Materman]

well, after rebuilding my master, getting all new wheel cylinders,building a garden sprayer bleeder and bleeding the brakes with it and using DOT 3 brake fluid, I STILL have no pedal. any suggestions?

[Materman]

I also followed the proper bleeding sequence...... pass. rear, driver rear, pass. front lower, pass. front upper, driver front lower, driver front upper.

[ptwothree]

Is the brake pedal free play set correctly?  Did the master cyl ever get empty while bleeding?  Are the brake shoes adjusted.  Any other work/mods done to the brakes?  Were you getting steady steams of fluid from the whl cyls with no air bubbles?

[Materman]

freeplay is set correctly as per my manual, m/c never ran out, shoes are set where they are barely dragging the drums, and there was a nice clean stream of brake fluid coming from each wheel cylinder with no bubbles, also went through about 2/3rds of a gallon of fluid to make sure all contaminates were out of the lines. the only other thing that I have done to the brake system is reline the shoes.

[ptwothree]

 I would plug off one of the outlets at a time on the m/c and see if you can isolate if it's the front or rear systems that have a problem.  Or, plug off both outlets and see if you can get a solid pedal.

[mopar_earl]

Maybe your master bore is bad or internal valving. I'd buy a new master and not bother with rebuild kits.

Earl

[Dave72dt]

There is a specialized tool for setting the brake shoes.  A number of members here have them and some rent them for use.  From all the posts on poor brakes, it appears the tool is necessary to get them adjusted and have proper pedal height, and brake performance.  I did not see mention of using the tool for setting them or having the new shoes arced to the drum.  Not having them arced or setting them by feel can result in using all the fluid the master pumped just for getting the shoes close to the drum and not enough to apply any pressure.

[mopar_earl]

Do you have a low firm pedal that pumps up firm? Or do you have a spongy pedal? If its a firm pedal and it pumps up firm, its a travel/adjustment issue. If spongy, air. Don't over look the brake hoses. They can appear OK but have internal issues. They can swell and cause low pedal. Also if your keeping your original single circuit brake system, you will want to replace everything. All it takes is a leak or rupture and you have no brakes. Also go over your parking brake as its your emergency backup brake.

Earl

[dale]

I run a hose from the bleeding valve on the brake cylinders to a glass filled half full with brakefluid with the hose under the surface so I can see the air coming out.  When the air bubbles stop close the valve and move on.  After a few slow pumps keep the master cyl as full as possible.  Works best when you can get someone to push the pedal while you are at the brake cyl.  I also agree you should buy a new master cylinder.  This should be only a fifteen minute job.

[Materman]

it is just spongy, haven't got it to build any pressure as of yet, and I did get around to replacing all rubber lines recently, so that can be crossed off my shopping list haha. I guess its a master cylinder then, I'll let you guys know what happens next.