Brake question for people way smarter than me? (1 Viewer)

[brew8]

I'm working on likely a 77 FJ40, kind of a hybrid setup I have replaced all the rear wheel cylinders, the front calipers and the hoses, I have inspected everything for leaks. I had a replacement LC master cylinder and a LC brake booster,, some kind or device to regulate the rear brakes stock thing. The Booster was replaced with a mini truck booster (wouldn't hold vacuum) and I have tried a new Mini brake master cylinder as well. so no blocked lines etc., all was bench bled properly and the rest of the system bled, I adjusted the plungers some but it doesn't seem to change things.

Symptom's' When you push the pedal with the engine running the booster in play the pedal goes to the floor will not harden up. Keep in mind I have rebuilt maybe a dozen brake systems on Land Cruisers, always able to solve problem.

So

Bad new wheel cylinder in rear?
3 bad master cylinders in a row?

I'm sure its right in front of me but I'm getting older so WTH is going on,, Cheers in advance, Larry

 

[bikersmurf]

Which MC are you running now?

Booster should be fine and wouldn't cause your symptoms. It's either adjustment or air in the lines.
Some rear cylinders don't have the bleeders at the top and still have air in them even after bleeding.

I'd tighten the adjusters till the shoes are tight to the drums and see if the symptoms change.

 

[brew8]

good ideas, mini truck MC right now.

 

[SteveH]

My rear brakes ('78 FJ40 stock setup) were super-sensitive to proper adjustment. After much fiddling, I got my brake pedal back (it was diving to the floor). Spend due time on your rear brakes and try adjusting until you can just barely slip the drum over the shoes. Mine had to be very tight for me to get my pedal to stop going to the floor. I have done brakes for 30 years, too, and was really tripped up my an MC and rear shoe replacement on my FJ40.

 

[Avattack]

I had the same problem after replacing MC, brake booster, and knuckle rebuilds. I read many forums and proper brake adjustment in the rear is how I solved it. Kept adjusting until the wheel/tire locked up, then backed off 3-4 clicks. Worked both sides until my brake pedal was stiff. Took me a lot of brake fluid and bleeding until I figured it out. Gook luck!

 

[brew8]

Yea, I adjusted them too full stop on the drum 3 times after centering the shoes each time, I'll try again see if it helps, might go back to the lc master might have more volume of fluid for the rear.

 

[brew8]

anyone use those vacuum bleeders, just curious

 

[bikersmurf]

anyone use those vacuum bleeders, just curious

I've used a vacuum bleeder in the past, they make it much easier to flush a lot of fluid through the system. I've found them to be quite useful to get all the air out... some have found they're not the perfect solution.