Help! No Brakes!!

Had a rear brake cylinder go out a couple weeks ago. Drove home with brakes getting worse all the way. I thought I would keep front brakes but they went out as the rears lost fluid. Replaced the rear cylinder and bled them out as normal. Test drive and brakes are soft and go to the floor. Will not lock up wheels on dry pavement.

Setup is:
hanging YJ pedals with power
Front is late 70s D30 Disk
Rear are early 70s 11” drums.

These brakes have worked perfectly for the past 3 years including one trip thru the Rubicon and many miles on Colorado trails. As well a thousand miles at home.

My best guess was a bad MC. Installed that yesterday, did an thorough bench bleed and had help bleeding the rest today. Brakes are no better.

So I’m stumped. I’m sure I was bleeding them correctly as I’ve done that many times. From the initial build to every time I’ve taken the rears off to grease the bearings.

Thanks for reading. Suggestions for the next step are welcome.

 

Get speed bleeders.
Start at farthest point from master and work inward to bleed them. You most likely have some trapped air in your system somewhere.

also, just because your MC is new does not mean it’s not part of your problem.

 

I fought this and was getting straight fluid all 4 corners. At GeoffreyL 's insistence I pulled the front calipers off the brackets, put a block of wood in the caliper, bled again with the bleeders pointed straight up. Got a lot of air out of both fronts. You can put your face through the windshield now.

 

I’m sure I was bleeding them well. I use a clear plastic hose on the bleeders to see if any bubbles are coming out.

I considered the new MC was bad but since the brakes were exactly the same before and after I think it probably wasn’t the problem.

 

That’s easy enough to try. It’s just baffling as the fronts never ran out of fluid and I have never had to do anything like that before.

Is there a reason I also lost front brakes when the rears lost fluid?

 

A new MC is a bitch to get bled. Even with the bench bleed, (and make sure you do that at a slight angle up), once you disconnect and reconnect the lines, there is air. In my experience, really tough to do on a dual circuit disc/drum without a pressure bleeder.

 

I used a Mighty Vac and had no problems. Peddle is hard as a rock. Used on my clutch and M/C.

 

Pretty much everyone thinks it’s a bleeding issue. I’ll go at it some more tomorrow. Thanks for the replies. Any other ideas?

Is there a reason why the front brakes don’t work when the rear goes dry?

 

The only thing that would really cause that is not having enough pedal travel before you hit the floorboards.

If the rear circuit looses its fluid, you need to completely bottom the rear circuit piston out before the front circuit can start building pressure. This can take quite a bit of pedal travel. It's something to consider when designing a custom pedal setup. You should ensure enough travel to not hit the floorboard in the even of a single circuit failure.

 

I've seen where calipers were mounted on the wrong side, and upside down, so the bleeder was not at the top. Just a thought.

 

I have a mighty vac and I still go back to my clear hose and a pickle jar.. My son thinks I'm weird..

 

This is how I always bleed brakes!

 

Mityvac it is. Stand by for results.

 

I was going to add to check and make sure you have your push rod adjusted correctly.

When I installed my YJ setup in my 2A I had to both modify the brake/clutch arms AND the floor board to get enough swing. CJ5s have more cowl height, so this is less of an issue, but still, make sure you have enough push rod length.

 

I’m pretty sure it’s good. The brakes have been awesome for a few years until this recent failure.

 

Was having troubles bleed brakes when I put everything in new.
Start over again. Undo the brakes lines from the MC and put the small short lines in so you can bench bleed again. Do it while the MC is in the Jeep. You can sit in the Jeep and use your foot. Much easier and can do it for longer time. Use speed bleeders.

 

I may have to pick up that Phoenix system it sounds pretty nice.

 

Thats kind of my point. If you used a used master that was working and fully bled, then blew all the fluid out and changed it for a new master, you either have bad master Orings, too short of a rod, and or air in the system.

I chased poor braking in the same vein as yours and it was air in the system. You might have to do as Rich said and physically turn the bleeder on the caliper straight up and as Steve said to bleed that master while IN the jeep.

 

X3 on removing a D30 caliper to turn the bleed screw straight up. I bled these on the axle with no air bubbles for over a dozen cycles. Then after pulling the caliper, putting a wood block between the pads, and bleeding again with the bleed screw straight up, I got more air bubbles out of both sides. Problem solved!
You have to look at the caliper to see where the highest point is in the piston bore where the bleed hole is.
Another trick is to squeeze the piston all the way back in the caliper, squishing all the air volume out before you start to bleed the caliper. This way, there is almost no air to bleed as the caliper fills with fluid. This is the only way to bleed a BMW clutch slave.
-Donny