Drum brake refresh, weak braking on the first pump. What am I missing?

[aging fleet]

I'm posting this as a sanity check before I go crazy bleeding my brakes.

The guilty party is a '75 FJ40 with its original 4 wheel drums. I recently replaced all 8 wheel cylinders, shoes and soft brake lines in an effort to get the drums working as well as they were intended. Per the FSM, I have them put together correctly with the left hand thread cylinders on the passenger side and oriented as illustrated below. I've bled all 4 wheels solo, with one of the kids pumping the brakes, and with my motive bleeder (that universal adapter is the worst).

I followed @Coolerman's bleeding method, the cylinders were adjusted to the point where the shoes were snug when I installed the drums. For final adjustment of the shoes, I tightened evenly until the wheel wouldn't turn, then backed the cylinders off about three clicks each. I can spin the wheel, but there is contact between the shoe and drum. Pedal height was on point per the FSM specs.

Currently, the first pump of the brakes goes almost to the floor, second pump is firm with about an inch less travel and no bleed down. If I wait few seconds, I loose the firm pedal feel. If I clamp the rear body to axle soft line, I don't get nearly as much pedal travel and the feel is firm. I assume this means I still have some air hiding in those rear cylinders, any tips for clearing it out, or is there anything I'm missing?

Thanks,
Brad

 

[middlecalf]

Did you start bleeding from the furthest away cylinder first, which I believe is LRF cylinder, then proceed forward? Was the MC bled (bench or insitu) first?

on edit: don’t know if a ‘75 is a dual circuit or single, so answer to that determines where to start bleeding - always furthest.

 

[aging fleet]

Did you start bleeding from the furthest away cylinder first, which I believe is LRF cylinder, then proceed forward? Was the MC bled (bench or insitu) first?

on edit: don’t know if a ‘75 is a dual circuit or single, so answer to that determines where to start bleeding - always furthest.

It's a dual circuit on the '75 and I did not bench bleed the master. My bleed order was LR, RR, RF, LF.

 

[middlecalf]

MC air needs bleeding out.

 

[aging fleet]

MC air needs bleeding out.

Thanks @middlecalf, seems like a logical next step given the amount of fluid I've put through the system.

 

[Skreddy]

Is the master cylinder new? If no, disregard and bench bleed first.
If yes, is it the proper master with residual valves for drum brakes?

 

[aging fleet]

Is the master cylinder new? If no, disregard and bench bleed first.
If yes, is it the proper master with residual valves for drum brakes?

@Skreddy, I did not change the master so assuming it’s the correct one. I’ll post a photo when I get back to the house.

 

[Pighead]

Try adjusting the shoes closer to the drum a click or two. See if that changes the pedal any.

 

[StephaniesFJ]

I had similar symptoms (but I have disc and drum 78 FJ40) but I tried everything - calipers, bleeding like crazy, new MC new BB....... everything.... so my last ditch, thinking out of the box, it actually worked for me....... it ended up fixing after I rebuilt my carb because the gasket at the bottom of the carb was causing a vacuum leak that was just big enough to keep from building enough pressure..... but if I gave it time and pumped the brakes I could get some brakes, but then they were back to nothing.... so if nothing else works..... the gasket on your carb. Sounds dumb, but it was my fix after trying everything else.

 

[aging fleet]

Master for reference and I’m off to do a bench bleed. @Pighead, I’l try tightening the wheels down again too. Thanks everyone.

 

[AntFarm]

You’re on the right track. MCs have a way of hiding an air bubble. Let me add one thing that I’ve learned. Just because a wheel is locked up doesn’t mean both shoes on that wheel are fully tight. Adjust a single wheel cylinder until the wheel locks up then back it off just one click at a time until you can spin it with a dragging shoe. Now, repeat that with the opposing wheel cylinder. You now have both shoes adjusted as tight as they should be. There will be a lot of drag. More than you think there should be. If your shoes are new you’ll wear off some of that surface grit on the first test drive. They will smell warm, but not burning.

 

[Pighead]

There will be a lot of drag. More than you think there should be.

Yes, that much.

 

[aging fleet]

Yes, that much.

Thanks guys, the bench bleed and subsequent bleed on all 4 corners didn't resolve the issue but at least I can cross the MC off the list. I've got another hour to mess with it before the wife starts barking so I'll prioritize adjusting the shoes.

 

[aging fleet]

@Pighead and @AntFarm, I haven't driven it yet, but the pedal feels a lot better after re-adjusting the shoes. Not sure what I missed, but sure enough, the front shoes were way too loose.

With all the flushing I've done over the past week, I'm pretty sure I have the cleanest brake fluid in the Midwest. Beer time....

 

[aging fleet]

To close the loop on this, I put a few miles on it today and the brakes work great. Way more confidence inspiring than prior to the teardown, thanks everyone.

 

[StephaniesFJ]

I updated my list from what you guys gave me and what I normally carry. Everything on this list fits in this picture!


- CASE OF PALE ALE
- gloves
- ratchet straps - I’m a girl so this is a must when I don’t have a guaranteed corn fed boy there to break a bolt loose. Wrap one side around the ratchet handle and the other around a tire or axle and get to cranking - dads teach your daughters this, it has saved me so many times.- vice grips
- LED magnetic light
- set of basic wrenches/sockets
- I carry a tool you can get at Ace that is a pry bar, hammer, crescent wrench in one (Stanley Fat Max)
- leatherman
- bailing wire
- RTV
- thread locker and super glue
- piece of jumper wire with a wad of gorilla tape wrapped around it (works as duct tape but I’ve been told its not conductive so it can be used as electrical tape to get you home)
- a spare piece of fuel hose (can be used for so many things)
- jug of premixed anti-freeze
- zip ties
- a set of basic toyota bolts
- hose clamps
- small critical parts like fuel filter, u-joint, belts
- steel stick
- breaker bar / cheater pipe
- small tire repair kit
- Jumper box that’s also an air compressor (Stanley Fat Max is also a phone charger, pressure gauge, flash light etc - I can jump a good sized diesel tractor three-four times before I need to put a charge on it)
- small can of starting fluid
- small bottle of brake fluid
- small can of WD-40
- quart of oil
- can of seafoam

 

[StephaniesFJ]

welp.. I meant for that to go on a different thread......

 

[aging fleet]

welp.. I meant for that to go on a different thread......

But now I know you always carry a case of Pale Ale which could be helpful.

 

[dazerb]

You'll get invited on every run

 

[John McVicker]

Right or wrong, here’s how I tighten my 4 drum brakes on my ‘75 40 that I bought new.

I tighten each wheel evenly until the wheel won’t turn…this is done with the wheel/tire on the truck & in the air. Then back off ONE CLICK only.

Do this to all 4 wheels.

Then go for a test ride…go for a ride in a secluded area, ride for several miles…do NOT use your brakes. Then coast to stop…coast, try to not use your brakes to come to a standstill.

Quickly jump out & feel for heat at each wheel. At this point I want them to be warm. Warm, not cool. If not warm, make necessary adjustments.

These rigs with all 4 drums are tricky to get adjusted properly, this is how I have done it since reading @Poser thread years ago.