Brake trouble shooting

My 58' cj5 134 f head has been rebuilt for a year now and the brake are giving me heck, the jeep runs great but, it stops tot well and does not quite stopping......

I put new wheel cylinders on her new shoes new springs, and dot 5 fluid, bleed and bleed and bleed the brakes, I am running 11' drum brakes from a willys pickup/ wagon on the front, i get the same symptoms every time.

The brake Pedal engages at 1/4 of the way down and after one full pump the pedal is stiff and will not depress again.

My brakes grab and do not let go until some time passes ( a few hours ) or when i continue driving after stopping the brakes bog down the motor until the friction is over come, the passenger side is worse than the driver side and cause the jeep to swerve to the right but both side grab and stay grabby.

I have not replaced/ rebuilt the Master cylinder. I am ready to throw more parts at it, Does this sound a MC relief valve problem?

Holidays are jeep times

Pete

 

How did the brakes work before you installed the 11" inchers?
If okay before, then I would rule out the master cylinder.
Those brakes will be manual cam adjusting and they need to be right on the mark.
Are the brake shoes installed correctly?
Did you turn the drums"
Grease or brake fluid on the shoes?
I would be pulling the drums back off and doing a visual of all the parts before doing anything else.
Do not apply the brake pedal with drums removed.

If all of that is okay....
It could be the master cylinder....during bleeding, if the pedal went to the floor, the piston inside the master cylinder would have extended through an unused/rusty portion of the bore and damaged the piston and/or seals. It could also be binding in the bore.

 

how are the hoses running to the front ?

 

Pete I have put on 11 inch drums from a wagoner, on the back of my CJ and I get the exact same symptoms. I think the stock MC does not generate enough force. Not sure though - what I do know is having a working stock MC did not help in my case.

I have ordered the dual MC conversion kit from R&P and it should be here soon enough. If it helps I will post and let you know if you have not worked it out yet.

 

Stock MC generates enough force if the brakes grab and don't want to let go....

 

"I think the stock MC does not generate enough force."

Enough force for what? Sounds like it is the release that is the problem, not the application. I'd agree with jpflat2a, the MC piston may be binding.

 

Crack the line loose coming out of the master when the brakes are locked. If they release, bad MC. If still locked, bad brake hoses- they collapse on the inside, no matter what the outside looks like.

 

"Crack the line loose coming out of the master when the brakes are locked."

Good idea. Unlikely that all four hoses would collapse at one time, I would think. I've never seen it even once.

 

Did you have the shoes arched? or ground to the correct inside diameter of the Drum? If not I have seen the leading edge of the shoe bind up against the drum.

 

What happens with mine is the stock MC can't generate enough force unless you pump it. It will hold for a little while but then fade. I thought I just needed a good bleed for the longest time but I finally realized what was happening.

I can lock the tires up, but only if I pump the brakes once or twice first

 

That sounds more like a worn out MC IMO.

 

I installed a new master cylinder and didn't realize you needed to adjust push rod. The master cylinder would work but get terrible brake fade really quickly, much like you describe. I was bleeding the brakes all sorts of methods even did it exactly according to the factory service manual. I forgot how I figured it out but I adjusted the push rod and that problem went away and that single reservoir has enough pressure to hold regardless of ten or 11 inch brakes.

If its been rebuilt well, I would say the master cylinder could be questionable I was having trouble with the one I rebuilt. I learned replace stuff like that don't bother rebuilding.

to the original poster: like other said do a brake inspection, pull of drums and check those springs and the hold downs for the shoes.

 

Hi Pete...if you're ready to throw more parts at it, throw a new master cylinder in it. I just did R&P's Dual kit & it took about 3-4 hours. If the hoses are old/stiff/cracked, replace them. Prior to doing my brakes, I had similar problems with pulling to the side when applying the brakes...first to the right & as more pressure was applied it would pull to the left. (Kinda scary) I've never been a mechanic but the advice I got many years ago was to make sure the drums on each side of the axle are turned to the same dimension & that the shoes are properly mounted...what I mean there is that one half of each side may have a longer pad...& that the longer side should always be to the rear...how valid that advice is, I don't know, but it has always worked for me. You also say you have replaced the springs & that may be part of the problem too...take a look here... http://www.earlycj5.net/forums/showthread.php?105127-Brake-Drum-Issue/page2

 

What Miner's saying is that with most simple drum brakes, and I'm guessing that a CJ5 is one of 'em, there is a leading (front) and a trailing (rear) shoe, the leading shoe needs to be shorter because with the cylinder at the top the front shoe will want to try to jamb up the drum and brake very aggressively with the drum rotating forwards. I have run into rubber brake lines that have broken down on the inside but look fine on the outside. When you apply pressure they will let fluid pass but not return, effectively locking that brake for some period of time until it bleeds off. FWIW

 

Where the longer and shorter brake shoe belongs depends on the type of brake drum system - it is different for self adjusting and non self adjusting. Normally it will be the shorter in front I think

 

It depends on where the "action" to move the shoes out is mounted, with the cylinder on top the front shoe will try to grab the drum and rotate with it, whereas the rear will just be pushing against the drum, the direction of rotation will not try to force the rear shoe out any further. If the cylinder, or any actuator for that matter, is mounted on the bottom the rear shoe will be shorter, but I can't think of an example of that. A double trailing shoe system uses a cam at the top and the bottom, the top cam pushes only the top of the rear shoe out, and the bottom cam pushes only the bottom of the front shoe out, making both "trailing" shoes so you can use a shoe with maximum surface area with no worries about binding. Off the top of my head the only example I can think of is my '71 Honda 350.

 

"A double trailing shoe system uses a cam at the top and the bottom"

I recall on British bikes at one time a dual leading shoe was the hot set-up.

 

Wow, I have lot of things check and suggestions to consider, appreciate all the feedback. To confirm, I'm running the stock single reservoir master cylinder. I have only run the 11 inch drums on the Jeep in it has it never stopped consistently for me since I I've got it.
if I bleed the brakes after they've locked up at the wheel cylinders they do unlock and do not catch/ grab anymore so does that mean my problem is with my master cylinder?