Trouble Bleeding Rear Brakes

OK we replaced a rear wheel cylinder. Can't get it bleed. Took line out of cylinder as to bypass bleeder. Nothing coming out. Pedal is still tight, not going to the floor. At a loss.

 

Line restricted somewhere.

 

definitely a restricted line, I'd assume one of the rubber ones.

 

Isolate the issue. Use a helper to push on the pedal.
Dual MC:
Start by loosening the rear brake line at the MC.
Push on the pedal.
Does the pedal drop (pressure at the fitting)?
If no, then the issue is in the front.
If so the issue is in the rear.

If you have pressure, re-tighten the line and move to the rear soft line.
Loosen it and press on the pedal. Does it drop?
If not then you have an issue with the hard line from the MC to the soft line.
Of so, re-tighten and loosen one of the hard lines at the junction block on the axle. Do one, then the other. If you have no pressure, then you have an issue with the soft line.
If the pedal drops, then re-tighten and loosen each hard line at the wheel cylinders. If the pedal fails to drop, then there is an issue with that hard line.

If it is a issue in the front:
loosen the front line at the MC.
Does the pedal drop? If so, tighten the line and move to one of the front soft lines and loosen it.
Does the pedal drop?
If so, move to the bottom fitting and try again.
Does the pedal drop? If not the soft line is bad.
If so, then move to the wheel cylinder and crack the fitting. If the pedal doesn't drop, you have a crushed/clogged hard line.
Repeat with the other side.

The troubleshooting is the same for a single MC only you will have to move to the front/rear junction block after checking the hard line from the MC.

Usually these issues are a soft line. If so, plan on replacing all three of them.

 

Thanks all for your response. I have verified that the hard and soft lines are clear, blew compressed air into junction at axel. Still no luck in getting rear to bleed. In disconnecting rear line from master cylinder ( dual ) I can get fluid coming out but, not a nice stream, just spits it out. Just to compare I can get a nice stream out the front. Do I have a bad master cylinder or am I missing something obvious. Thanks.

 

Is there free-play in the pushrod and master cylinder piston? May not be retracting far enough to uncover the fill port.

 

Believe that it is retracting enough. I am able to push out fluid for back reservoir just not a strong stream. It's not pushing enough to get it to the rear.

 

Either the MC need to be bled or you are sucking air through the rear seal.
Try bleeding the rear first. If it continues to blow air, then you may need to either clean and/or hone the master cylinder or replace it.

 

x2

 

OK. Fast forward. It is a clogged rear flex line. Been verified. Does anyone have a known source for replacement? Thanks in advance.

Matt

 

This is what I put on my 71 with disc brakes Napa Part #: 36761

 

They are available from just about any Jeep parts supplier. The last ones I bought were from QTM, but I have also bought them from Classic Military Vehicles, and RFJP.

CMV has a complete set for $30. Whenever I do a brake job on vehicles this old I always replace the brake lines to avoid trouble such as you have encountered.

https://jeep1942.com/?page_id=7361

 

Found one through Jeepsterman.

 

Update. So after much to do Ayden and I finally got the brakes back to 100%. New master cylinder, new wheel cylinders on all 4 corners. New rear brake lines and flex hose and new front shoes. Ayden did most of the work and I am so proud of him. He is really good at problem solving and execution.