brakes... I hate them... can you fix them?

tripped38

tripped38

Well-Known Member
Joined
Jul 9, 2008
Location
MI
I am trying to sort out the brakes on the bass boat build. So far I have nothing.

What is in place...
CJ vacuum booster. CJ pedal and assembly.
86 e350 master cylinder. This is the second one. bench bleed following the directions and it felt like it built pressure.
all new lines.
Axles are from an early 80's one ton. disc front with new calipers. rear is drum with wheel cylinders replaced.

I had a cutting brake in the picture but I have since by passed it as I thought that is where my problem was. I used a soft line to by pass it.

power bled. getting a steady fluid stream from the bleeders at all wheels.

I have double checked all fittings to make sure there are no leaks. I can't find a leak.

The issue is that I can't get the pedal to build pressure. when the jeep is off and you pump the pedal up it becomes firmer but the pedal still falls to the floor with steady constant pressure.

When the jeep is on and the booster is hooked up the pedal can be pushed to the floor with your finger. It doesn't seem to be building pressure.

I am at a total loss. This is the only thing stopping me from testing it and getting some trail time on it.

Basically I am frustrated with this thing.... and can't figure it out....
 
This is going to sound really stupid but I had a buddy with a similar problem and his issue was when he was bench bleeding the master he wasn't fully pressing the shaft all the way in so effectively he was only bleeding the one circuit in the master cylinder.

Are you getting air in booth chambers of the master?
 
Both chambers had bubbles. I was pushing it in fairly deep.... I'm not ruling it out but the way it felt I really think it is good

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Ol' jeeps made a spacer for me.

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what Lee said
also
To bleed my front 60, I had to remove the calipers, and put a 2X4 in place of the rotor to get all the air out. turning it different angles.

You said new lines, it may be that you went with too big of line and that you don't have enough capacity on your cylinder plungers to build pressure.
 
3/16 line I believe. I'll need to double check it.

What do you mean put a 2x4 in place.

I've used a power bleeder and also done it by hand with help.

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I had to remove the caliper off the Jeep, and put a 2X4 in between the caliper instead of the rotor, turn it to different angles to get all the air out of the capliper
 
Interesting. I'll try that. But would that explain why it isn't building any pedal pressure?

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Been pondering this, Mike. Think I may have found the answer.

First, make sure the rear shoes are adjusted up good. You could be using all your master cylinder/pedal throw to push the shoes out.

Second, You will probably need to put a 2 PSI residual valve on the front system and a 10 PSI residual valve on the rear system. The stock system has this built in. And since the specs an your master cylinder are the same as the stock master cylinder, I think you could be missing the residual pressure that would normally be there to keep the system ready to pressure up.

The calipers are retracted by the o'ring. So they retract very little unless the rotors have excessive run out, (which will push em back in further!). The 2 PSI residual will keep the calipers full so when you hit the pedal, you don't use up pedal filling the caliper cavity. Now the rear uses springs to retract the shoes. So the springs will retract the wheel cylinder back further yet, requiring more pedal just to fill the wheel cylinders before ever applying pressure to the shoes.

It occurred to me that if the fluid isn't leaking out or "going anywhere", the system absolutely MUST build pressure! Even if it is just spongy "air pressure" from an un-bled system, it still will have some pressure. It has to!
Unless.
The master cylinder runs out of 'push' before it can fill the system and hit the restriction of the brake pads/shoes and builds pressure.

I believe these two things will solve yer problem!;)
 
Ol jeeps! I think I should just bring it to you and let you work your magic. Thanks for the help guys. Bleeders are correct. Double checked them.

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I thought it as I typed it... I was waiting for the... that's what she said

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Jody Treadway said:
Any chance the bleeders are upside down? Happens to the best of us.
Click to expand...
I can second that. I know on a Jeep axle the calipers can be put on the wrong side. If the bleeders are on the btm, you can bleed all day long with no results.
 
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