CJ brakes

blackcj71 · Jun 27, 2006

I got a 77 CJ5 with front disc rear shoes, power brakes, and adjustable prop. valve for the rears. Brakes worked perfect until we swapped out the pos dana 30 for a chevy 44. Since we've done that it takes about 4 pumps to get alittle bit of pedal. I keep sucking air into the fronts and cant figure out where its coming from...Took the calipers back got new ones that didnt work baught new master cylinder thing it might be sucking air from the back that didnt work. Gone over every fitting making sure its tight and its tight. What am i missing?? I can pump it up and hold it tight and it doesnt fade away but as soon as i release and push pedal again straight to the floor. Any Idears:redneck:

spenser

NotMatt · Jun 27, 2006

I would be that you're not sucking air in, it probably just still has air in the line. Had this problem on a friend's rig after it sat for a while with no fluid in the system (same story... axle swap took a while to finish).

We ended up gravity bleeding it over the span of a few hours. Put a hose on the bleeder screw, open it up, and set the end in a container on the ground. Do that for both sides, top off the master cylinder, and come back in a couple hours and try bleeding it again.

Also, if the master cylinder has been empty for a period of time, it helps to "bench bleed" it. You also need to do this with a new master cylinder (not sure if you did or not but you didn't mention it). You need a couple short pieces of brake line with the correct fittings. Fill it up with fluid, and connect the short chunks of line back into the resevoir below the full line. Fill it up with fluid and pump or push the rod in until no more air bubbles come out. A lot of times it's tough to get the bleed process started if you haven't done this on a dry master cylinder.

blackcj71 · Jun 27, 2006

That sounds like the same thing that happened here swapped stuff out sat for bout 5 months then put the brakes on

We spent all day saturday trying to bleed this damn things ill try that and let you know if it works

And yes master was bled out both the old and the new.

NotMatt said:
I would be that you're not sucking air in, it probably just still has air in the line. Had this problem on a friend's rig after it sat for a while with no fluid in the system (same story... axle swap took a while to finish).

We ended up gravity bleeding it over the span of a few hours. Put a hose on the bleeder screw, open it up, and set the end in a container on the ground. Do that for both sides, top off the master cylinder, and come back in a couple hours and try bleeding it again.

Also, if the master cylinder has been empty for a period of time, it helps to "bench bleed" it. You also need to do this with a new master cylinder (not sure if you did or not but you didn't mention it). You need a couple short pieces of brake line with the correct fittings. Fill it up with fluid, and connect the short chunks of line back into the resevoir below the full line. Fill it up with fluid and pump or push the rod in until no more air bubbles come out. A lot of times it's tough to get the bleed process started if you haven't done this on a dry master cylinder.

junkyard jim · Jun 27, 2006

If the calipers are much larger than the original ones, then the master cyl's volume won't be able to keep up. You'll push it down past the point that the relay port (or whatever they call it. Been awhile since I looked at a diagram) holds pressure in and it will be released into the front half of the master's reservoir. (when you pump it, you overcome the volume problem till it can hold)

Hip · Jun 28, 2006

you need an 1 1/8" bore master cylinder. what size came on the vehicle?

my cj had a 1" bore and it wasnt enough. the 1 1/8" did the trick.

blackcj71 · Jun 28, 2006

Hip said:
you need an 1 1/8" bore master cylinder. what size came on the vehicle?

my cj had a 1" bore and it wasnt enough. the 1 1/8" did the trick.

Ill check that out where your brakes totally dead?

blackcj71 · Jul 1, 2006

Still not working! Tried what notmatt said and also picked up a Brand New master from a corvette and still the same problem! Whos the brake guy around here?