'66 Cj5 Tux Resto-mod

@Fireball what is the right way to determine how long the pushrod should be?

 

It's not easy to tell where the piston is in the master cylinder, so your best bet is to make sure there is a tiny bit of looseness in the pushrod. If you can pry the boot off the back of the master cylinder, you can look and see if the piston returns all the way to the snap ring but access to actually see it might be difficult while it's in the Jeep with the body on.

 

Well I started out this morning by backing off the jam nut and then backed off the push rod as far as it will go.

If I reach down below the steering column and pull the pedal back it moves about 3/4 of an inch back, and then when I let it go the pushrod rests on the cylinder so there is some Free play there.

I am now able to push fluid all the way through the rears so I think I solved the flow problem. The pedal is still spongy though so I’ve got some air somewhere. I don’t think the bleeders on the front calipers are in very food shape so I’m going to FLAPS to put speed bleeders in the front and that should do it (I hope).

EDIT: nope. I actually crawled under there and had a look and there is about a quarter inch between the piston end and the snapring. So the push rod needs to come out and be cut. Working on that now

 

Putting the body on probably lowered the pedal causing this. It's good you found it now. It can lead to severe brake drag if the master cylinder doesn't return all the way.

 

I think I’ve made some major progress. I’ve got speed bleeders at all four corners, and I’m pushing out clear fluid. Increasing or decreasing the proportioning valve seems to change the fluid flow through the system, but the pedal is still fairly soft and spongy. This means there’s still air in the system somewhere right?

 

It sounds like it. Manual brakes should be pretty firm. Sometimes it helps to pull the calipers off and put a block of wood in them (to keep them from pushing the pistons out). Then you can rotate the caliper to get the bleeder as high as possible. It's also possible there is still air in the pipe loops over the frame. That's a long way to push a bubble so you may have better luck cracking the fittings where they go into the distribution block.

...and it's possible the master cylinder needs to be bled if none of that works.

 

The bleeders can’t really get any higher on the front calipers.

I think I’m done working on the brakes until I can coerce a buddy to come help me. Back to wiring.

 

I went camping and came back and you guys have made good progress. I would add, for whatever reason new front calipers hold bubbles, give them a few taps with a hammer when you have the bleed tube connected, sometimes that will release some air.

 

Where did you go camping Tim?

if you wouldn’t mind can you double check me on my heater hose routing? Right now I have the line that comes from the side of the Mojave that is closest to where it mounts (call it “back”) where it says “in” going to the top of the intake manifold, and the other line from The water pump sucking in cold coolant water from the “front” out port of the heater. Is this right?

 

i went on the Vintage 4x4 Expedition, down in the foothills. All kinds of old rigs, I took my Dodge M37. Nice to get out of the snow for a few days. Yes, I think you have the heater right, hot from the manifold in, back to the water pump out.

 

Well I had a buddy come by and we tried to bleed all the air out of the brakes but despite trying for about an hour, whatever air was in there has gone from a couple bubbles to a million tiny bubbles, coming out of all four corners. What my next move do you think, just try again and keep pushing? We were careful not to rapidly pump the pedal too.

 

Now that you have fluid making it to all 4 corners all you should have to do is back off one speed bleeder a 1/4 - 1/2 one at a time and give the pedal 5 or 6 slow presses. If you are still getting bubbles air is getting sucked into the system somewhere.

 

I was thinking back to my building giant fire cannons at Burning Man days when we used to spray soapy water around pipe fittings to see if any propane was escaping by blowing bubbles.

We built this full scale replica of a Spanish galleon and didn’t kill anyone!

I know I wouldn’t want to put soapy water on brake fittings, but is there a way (brake fluid?) to observe all of the fittings while someone is pumping to see if air bubbles are coming out?

 

I bet your fitting connections are fine or they would be leaking. My guess would be the master or proportioning valve. Did the pedal firm up afte the big bubbles were bleed out?

 

I was actually lying under the Jeep, not operating the pedal so I'm not quite sure. When we stopped and everything was closed, the pedal is softer than it was. FWIW I had the PV all the way open (up, counterclockwise) during this session. I turned it all the way in after we quit (clockwise, down) to see if there’s a difference and the pedal gets significantly harder.

So at this point would you recommend that I keep bleeding the next time I can get a friend, or will I be chasing my tail forever and I should just stop and disconnect the PV and master and bench bleed them and start over?

 

This helped me.

 

I would bench bleed, then be sure there are no wet fittings anywhere, including wheel cylinders. Adjust all shoes to be rubbing on the drums. Then only work on the right rear. See if you can get it to stop sending bubbles. If it won't improve, there is no point in moving to other wheels. And you have the MC cylinder returning all the way?

 

Yes I have full return to the snap ring, and then about 3/4 of an inch of FreePlay where I can pull the pedal back from under the steering column. I don’t have the return spring installed to the crossmember yet though. What I’m wondering is if I got a bunch of cavitation in the master cylinder from the period of time was pumping a lot but the piston wasn’t returning… So I think starting over by bench bleeding it is the way to go.

 

I would start over bench bleeding. I have had bad new master cylinders more than once giving me fits trying to bleed also, so don't rule it out.

 

Funnily enough I was discussing this with the guy that rebuilt my engine and this is what he said:

A bad master cylinder will do that. We chased air bubbles on a car one time and put three new master cylinders on it and they all had the same problem. We finally took the new apart and honed the bore and found that the bore had ripples in it which was causing it to put air in the line. After the hone we put it together and the problem was solved. The other thing you can do is just leave the bleeder screw open and not pump the brake and just let some fluid flow thru it then close it then try bleeding it. Keep in mind to only pump it a few times slow before opening the bleeder so you don't aerate the fluid.. Good luck!!