More Questions about CJ Brakes

dbesade

Okay, Stupid question, I have installed a new master cylinder, bench bled it, installed it, all new rear brake lines, and new shoes and wheel cylinders in the rear drums. After that I did more adjustments on all 4 drums and bled them 3 times. I still have very little stopping power, barely enough to keep it stationary in reverse. I would like some suggestions at this point. I'm thinking brake booster at this point. Thanks -Dave

Mudrat

Did you ever resolve this problem???? I'm still down 100+ posts from vacation and travel ... Pat

dbesade

Nope

Mudrat

Well, CJ's were made for years without boosters (actually a lot of cars were too!), but they had a large plunger in the MC for pressure. Did you replace the brake lines? Is it possible there is debris in them? Have the new MC seals failed allowing leak by? (I've actually had that happen with a new Chevy MC on my K-10 #-o ) Have you checked your proportioning valve? (left inside frame rail by the clutch bell crank) When you nail the brakes ‚Äì does it steer to one side (uneven braking)? Lets see if we can work though this one ‚Äì might be of use to others as well ‚Ä¶. Pat

Trailbst

If you have a brake booster, is there adequate vacuum to it. Does the vacuum valve still work properly?

dbesade

Okay,

There is no leaks in the Master Cylinder, I checked when I was bench bleeding it. Have checked again, no leaks past the seals. I did replace the rear brake lines, I bled them before I attached them to the drums so there wouldn't be any debris.

When I nail the brakes they do nothing, a slight stopping sensation but nothing more. I have to pump frantically for them to work correctly. How would I check the proportioning valve?

My CJ Has Stock power drum brakes. I have a booster on the way already, the one on my CJ is stock, as is/was ALL the brake parts.

-Dave

pyagid

dbesade wrote
I bled them before I attached them to the drums so there wouldn't be any debris.
-Dave

Did you bleed them again after they were attached? If not you will have air in your lines they need to be bled after attached to the wheel cylinder

-Paul

dbesade

Yup. Bled all around 4 times. -Dave

Mudrat

dbesade wrote
Okay,

There is no leaks in the Master Cylinder, I checked when I was bench bleeding it. Have checked again, no leaks past the seals. I did replace the rear brake lines, I bled them before I attached them to the drums so there wouldn't be any debris.

When I nail the brakes they do nothing, a slight stopping sensation but nothing more. I have to pump frantically for them to work correctly. How would I check the proportioning valve?

My CJ Has Stock power drum brakes. I have a booster on the way already, the one on my CJ is stock, as is/was ALL the brake parts.

-Dave

Frantic pumping to stop still sounds like an air build up or a bypass leak somewhere and you have to pump the pressure up :-|

Your not leaking anywhere are you - well, I mean your BRAKES aren't leaking anywhere -right? #-o

Do you nose dive any at all - even a little? Like the front is trying to grab and the back is just along for the ride?

If Yes, then it sounds like it's more in the rear brakes? If so check shoes and adjustment first, then the hydraulic actuators. (New, used, rebuilt?)

If No: then it sounds like the problem is at or before the p-valve and is affecting both front and rear brake presure. Either the MC, the 2 lines to the p-valve, or the valve itself. Check out the MP Brakes FAQ. They don't tell me how to test the P-valve, but do provide this tid-bit...
Q: What are the symptoms of a bad residual valve?
A: The brakes will be very spongy and you will need to pump the pedal to get good brakes.

Check this Trouble Shooting FAQ also ...

Does it get hard when you pump?
Is it a really soft peddle that hits the floor?
After it's hard, does it leak down under pressure?
And we are only talking brakes here #-o

Hope this helps

Pat

dbesade

Hey,

OKay some background is in order I suppose. This was my dads hunting rig back in Florida. The Previous owner before him was the Original owner of the Jeep so it hasn't passed many hands.

Since my dad has had it (about 4 or so years) it has had piss poor brakes. When he finally shipped it down to me I have done my best to correct the problems as they come and have been fairly successful. The tub itself is in pretty damn good condition for its age, just needs a new floor, side walls are immaculate as is the frame. It came from the factory with 4 wheel power drum brakes.

Now when I finally busted a brake line I decided to replace the entire rear (from the prop valve) half of the brake lines. I also installed a new Master Cylinder and installed new Wheel Cylinders and adjuster kits in the rear drums. When I pulled them off and did a good inspection, I realized the entire brake system was stock, from the factory stock. The wheel cylinders were leaking, the hardware in the drums was backwards (which explains the zero wear on the shoes which were also coated in Brake fluid).

So over 2 weeks in-between work and school I replaced the adjuster parts, shoes, wheel cylinders, brake lines, and master cylinder hoping it would at least boost the brake power. I am going to replace the Booster as well as its pretty damn rusted and gone.

Now,

I have NO leaks anywhere in the brake system, I have been watching. So I'm guessing from the information you posted there is still air somewhere in the system.

When I slam on the brakes at low speed the jeep does nose dive a little. Before all this work the rear drums were adjusted all the way in (on purpose) so they were not in touch with the drum as the wheel cylinders were fscked anyway and I didn't have the time to fix it). So the front brakes were doing all the stopping.

Most of the time when I slam on the brakes, nothing happens until I start pumping. When it does stop I hear a slight groan from the rear brakes and slight rubbing from the front.

It doesn't get very hard when I pump with no engine power and when the engine is running its very very very very to the floor with pinky finger soft.

P.S. I'll fix the picture in the mod forum 🙂

-Dave

Mudrat

dbesade wrote
Hey,
P.S. I'll fix the picture in the mod forum 🙂
-Dave

Why? I did for ya :wink:
And go ahead and give me a call if you want - but I would suggest looking at the Brakes links I gave above ... I had to replace my p-valve when I went to disks in the rear from TSMMFG and still have the stock unit if you need it.

Pat

dbesade

Okay here is the news, I got under there, sprayed all the drums with brake cleaner, adjusted them all, bled everything 2 times and prayed. I now can stop *IF* I ump the brakes. This seems like a brake booster issue to me, what do you guys think, I have one on the way so I am thinking I finally have this issue licked! Thanks for all the help! -Dave

fuzz401

when you bleed the brakes are you pumping them or just pushing them after the bleeded is opened = pumping is not good it can make the fluid foam up = air in the lines

dbesade

When I bleed the brakes, I am pumping the pedal until it gets firm-ish (as firm as it will get), holding it there, and opening the bleeder screw, (still holding) let the fluid/air out, retighten the bleeder screw, release the brake pedal. -Dave

Goose

Well This will sound stupid.. and it has nothing to do with your spongy pedal travel.. but I noticed in an earlier post you mention that the brake hardware was in backwards...Umm (and this is not a bust on you) Are you SURE?? I have put the shoes in back wards a time or two cause I was convinced.. they were in wrong.. and since most of the braking effort on a drum brake comes from the "camming" action of the shorter shoe vs the long shoe..if you have them in reversed, you wont get any braking action with ten boosters.. Believe me I have been convinced they were right and found they were wrong.. and you dont have to actually admit it..

dbesade

I replaced them via the instructions in my Haynes Manual and then checked them against the front brakes (which match the manual). I am 100% Positive the shoes are facing in the right direction. -Dave

dbesade

More updates, OKay I found a Jeeper near my house (finally), he came by and we bled the brakes another 4 more times, spewed a ton of air out, good stuff now I replaced the grommet on the power brake booster as well as the connector for the vacuum hose so thats all fixed (was leaking vacuum) and now, again, NO brake power. At this point I am thinking I might install the original master cylinder again and re-bleed the brakes, see if that makes any difference in brake power. It makes no sense, the only thing that could be not working is the master cylinder, its very possible that even though its new, it could be defective. Question now, do I try bench bleeding the new Master Cylinder again to make sure there is no air inside or do I just reinstall the old one (does the old one need re-bench bled as well?). Thanks -Dave

Mudrat

A: Install the MC,
B: fill it, open each wheel bleeder, and
C: get a beer.

Come back, check the level in the MC and look to see if your leaking DOT3.
If no = Repeat step 'C'.
If yes = shut that valve, then Repeat step 'C'.

Repeat as necessary until:
1 - 'C' is empty
2 - all bleeder valves have leaked and are secured

Test brakes in the driveway - if this process took a long time (it's called gravity bleeding) step 'C' will have filled the dwell time between steps 'A' and step #2 which will create additional issues with the operation of your Jeep. It is NOT recommended to proceed past your mail box #-o

But like I said earlier - I've had newly rebuilt MCs be bad from the git-go

dbesade

Hey Guys, before I went to work this morning I figured I'd see what happened after I replaced that Grommet and elbow for the booster, welp, NO vacuum leak anymore, in fact, with the engine off, I can hear the diaphragm and the pedal gets way stiff like it should and on top of that the brakes work a ton better with the engine off. Now when I turned it over, pedal to the floor way easily and no stopping power. This either means air (unlikely) or a fouled Master Cylinder. Whatchya think Mudrat, think I got a bad new master cylinder, you said it happened to you. -Dave

Mudrat

dbesade wrote
Whatchya think Mudrat, think I got a bad new master cylinder, you said it happened to you.

-Dave

Yup - OR your ported to absolute vacuum and not just an assist - but you can't stop and that scenerio would have you pull'n against brakes that were set by vacuum, and it would affect both front and rear brakes, not just your drums.

If it isn't the MC, I'm out of suggestions.

Good luck and let us know.