Am I on the right track?

[Colorado Boy-74-FJ40]

A couple of weeks ago I was coming to a stop when I felt a "Pop" and the brake pedal went to the floor. I felt the rig pull to the right. I mashed on the brakes a couple of times and they engaged very harshly. I carefully drove it home on side streets and had to pump the brakes three or four times to get a little if any engagement.There was no fluid leaking and my son and I had just recently adjusted all the shoes so I don't suspect bad / mis-adjusted shoes. I thought it was the master cylinder. I bench bled that and installed a new one and bled all of the channels until fresh fluid came out. Now when I push on the brakes the pedal is very soft the first time then when I pump the pedal again the brakes grab very abruptly and they lock up immediately. I feel like the front aren't engaging as much as the rear because the rear tires skid when I come to a stop on the test drive. I am thinking it may be the vacuum booster ? I an going to physically adjust all of the shoes again and bleed the system again including the master cylinder to eliminate the hydraulic end of the system. If all that is ok it has to be the booster...Right? When I pump up the brakes several times then hold down the pedal as I start the engine I do feel the pedal go in some but not as much as it used to i believe. Has anyone been here before?
It's a November 1973 FJ-40 With all stock brake setup.
signed Hot and bothered in Oregon

[rsbcruiser]

You Know what that sounds like to me Colorado Boy? Sounds as though one of your brake slave cylinders was stuck and finally worked itself free. Looky, that whole master booster asssembly thingy has been a nightmare for me. I finally pulled me head out me arrse far enough to figger it out. I took pics and all of my patented "read dorkmiester" method. Thinkin I could slather this post with pics OR. I have time free after noon, bring it over or viceEverse, nominal beer fee!

[FJ40 MNTCRZR]

Not sure but me thinkey, WHEEL CYLINDERS ... just a guess however they are a pain in the,,, if one is leaking just a little or sucking air. well let me say its just like women and fj40's.

If it has boobs or brakes they will give you problems.


GL

[Dirtsquirt]

its not likely your booster. the booster works to apply pressure to the master. so what ever is wrong or right with a booster effects
both front and rear.
since your rear brakes are locking up my guess is your problem is in
the front.. " I felt the rig pull to the right" Which indicates that at the least you have an inequality between the front. right engaging to much or left not engaging at all. I would pull both front drums and see if anything is amiss
The flakey spongy feel on the pedal that requires pumping could
be air in your front brake circuit. The other possibility is the seal
on the plunger for the front brake is blown.(Master Cylinder) Do you see air bubbles or what would appear to be fluid reentering the brake reservior when the brake is applied?
Good Luck..
I have had my cruiser around 4 mos. And I hope stop finding things wrong with mine someday..

[FF LC FREAK]

As others have said, it is not your booster. The reason you have to pump your pedal is that you need to move more fluid to apply the brakes than your MC can pump. I agree with RSB, it sounds like a stuck wheel cylinder came loose. Readjust your front brakes, bleed them and you should be good to go.

Good luck!

[e rock]

Definitely pull both front frums and see what's going on. The fact that the brakes "engage abruptly" makes me think that something actually went wrong in one of the two.

If you had a shoe lining separate on the left side, it could do what you describe. There are probably a lot of scenarios, but I'd start at the wheels before the master/booster.

[rsbcruiser]

Originally Posted by e rock

Definitely pull both front frums and see what's going on. The fact that the brakes "engage abruptly" makes me think that something actually went wrong in one of the two.

If you had a shoe lining separate on the left side, it could do what you describe. There are probably a lot of scenarios, but I'd start at the wheels before the master/booster.

Hey, e rock, have a buddy who live in Monroe, right by (not in) the Prison (inside joke). He drives Fords so.....

[rsbcruiser]

Come to find out, the hard way for me, this here rod has to be adjusted every time you replace the master cylinder. If you don't then things go down hill from there. The spec on this thing is 0 clearance to - 0.02". What that means is!!!!!!!! better to get it as close to 0 as posible.

[rsbcruiser]

First, You need to be sure your drums are in harmony (you know, like an OLD Rush song). Assuming your brake pedal is adjusted properly, and with the master off, pull that rod out from the front of the booster, did it have vaccum? resistance to extraction followed by an air escaping sound? Good sign I think, means booster is not leaking. Measure length to get yourself a baseline (not totally neccesary). There is a whole proceedure (read mega pain in the ass) that can be easily bypassed with a Billy Bob. This is it. Grab up your master, with pushrod in place, shove the master on there. Pay real close attention as the master comes in contact with the rod. Did the rod depress the master cylinder piston? That is bad. Did the master press against the booster with no noticable sping resistance? Could be real bad or just right. Case a, the rod is too long then every time you hit the brakes, brake pressure builds tell you can't move the rig. Too loose then permanent long throw in your brake pedal. Bla, bla, bla but you get the idea. Adjust the rod length accordingly.

[rsbcruiser]

Oh and one more. 0.02" is about a 1/4 turn or less on that length adjuster so it is real easy to get WAAAAAAAAAAAAY off. Bet it is too short therefore the root cause behind yuor long brake pedal throw.

[Colorado Boy-74-FJ40]

Update.
I finally got time to pull the wheels and I found that a lining had separated from the shoe on the right front. I am replacing both sides in case it was a bad lot. I also adjusted the rod out to where it just makes contact when the master is bolted up. It took about 3 full turns to touch. That explains the double pump problem. I also re-bench bled the master while I had it out. I will pull the rear drums off tonight to see how they look and then will re-bleed the entire circuit again I think I will have it fixed! I also put in my new rag joint last night. Look out here I come. Gonna take the top off the rig and go cruising....Finally!

[e rock]

Originally Posted by rsbcruiser

Hey, e rock, have a buddy who live in Monroe, right by (not in) the Prison (inside joke). He drives Fords so.....

We're not 'right by', but maybe a mile away or so. Close enough that we don't really need street lights at night.

Originally Posted by Colorado Boy-74-FJ40

Update.
I finally got time to pull the wheels and I found that a lining had separated from the shoe on the right front.

I win! Well, sort of. While it's lame that it happened, at least it was something easy to find, diagnose, and fix. IH8unknownproblems