Booster Issue?

[Boaf 32]

I only own a Haynes. .1 to .5mm (big typo). Downloaded the Drum Brake Booster Install Guide from City Racer: "Per Toyota spec, the clearance between the booster’s push rod and the master cylinder’s piston should be between 0.1 to 0.5mm (0.004 to 0.02 inch)".

Also, to test clearance: "Remove the four nuts holding the MC to the Booster. Hold the MC in position with your hand. Have an assistant push
on the pedal until the push rod moves the MC away from the booster. If the MC moves immediately, you have no gap. Shorten the push rod slightly until you can move the pedal a bit before the MC is pushed away from the booster"

 

[Boaf 32]

Here´s another idea:
Could it be that someone, someday changed work cylinder(s) to one with bigger bore and your stock master cant move enough fluid to fill this(these) big bore(s)?

It's hard to say, they look standard. I have ordered replacement for the remaining wheel cylinders and will try it...everything will be new.

 

[honk]

You asked above if there was another way to purge air from a brake system.

There is. Usually called "pressure bleeding" or something more proprietary. it is a system whereby a fixture mounts to the master cylinder in place of the fill cap(s), is connected to a reservoir containing brake fluid in amounts up to five gallons, which reservoir can be pressurized by compressed air, electric pump, or even a hand pump ala' bicycle pump.

The procedure goes something like this: the mechanism is set up onto a vehicle's master cylinder, all bleed points are opened and connected by clear rubber hosing to catch bottles which are only filled sufficiently to keep the hose outlet submerged. Then the pressure is applied to pump fluid through the entire system simultaneously until no air is emerging from any of the submerged outlets. At that point the bleed points are closed and the equipment is removed. The master cylinder is topped to its fill line and closed.

Such equipment is available for purchase. Most consider it too costly for their one time or occasional use but it is a standard piece of shop equipment at many professional repair facilities.

Care must be taken to assure that no air may reenter a system during any time which any bleed point is open, but that is a basic part of bleeding air from any system which operates by hydraulic action. Air is much more compressible than a hydraulic fluid; that's why it has to be removed.

 

[Boaf 32]

Well that's a neat trick. Your right,standard at the garage, not the home. I like the idea....

 

[honk]

Well that's a neat trick. Your right,standard at the garage, not the home. I like the idea....

If you like the idea there are alternatives to the high prices of professional equipment. Harbor Freight offers a version as do most any large auto part retail outlet such as Jeg's or Summit Racing. Also, many people have taken the idea and devised homemade versions of bleeders using anything from a garden sprayer to a gravity pressurized milk jug. If you are interested in exploring such things YouTube has several videos by various makers describing their solutions to the perceived need.

 

[Boaf 32]

All,

Purchased a reverse bleeder from Phoenix. Nice tool, crappy delivery though.

Bleeding:
Reverse bled starting at the Right Rear, then moved to the Left Rear. Then to the Right Front Front, then Right Front Back. Moved to the Left Front Front, then Left Front Back. The tool worked well, however...

I still have no brakes, the brake went to the floor. So that said:

Next Steps:

1. Disconnected the brake hoses from the Master and re-bench bled the master by connecting temporary clear hoses back into the Master reservoirs.
2. Continued pumping the brake until there were no bubbles in the lines
3. Re-attached the brake lines and added some sealer tape to the line threads just to be sure.
   
4. Tried brakes and still nothing.

SO after two (2) hours, called it a fricken day. Tomorrow, I will have an assistant help re-bleed the brakes from inside the truck (old school bleeding). Hopefully, the brakes did not work because air re-entered the lines...but I seriously doubt it.

I will wind up taking it to a local yocal to address the brakes. Does anyone have any last minute suggestions for the brakes on this MF-LC?

Boaf

 

[JohnnyC]

These three adjustments are correct? And spring is in place? Not a lot of free play

Crude photo ... Don't have my flash drive with me for FSM pic or measurements

 

[Boaf 32]

These three adjustments are correct? And spring is in place? Not a lot of free play

Crude photo ... Don't have my flash drive with me for FSM pic or measurements

View attachment 1202358

Thanks, yep all three within spec.

 

[JohnnyC]

I recall you saying you replaced the master cyl... Is it a teq unit or no name? What is its part number? So I can check if you have the right master...

Did you happen to check if you had the residual valves inside?

Under the plug (where the line attaches to the master) if you unscrew that you should have a washer between the plug and master and against the plug is the residual valve then under/in that will be a spring

The residual valve keeps a slight amount of pressure to hold the drum cylinder cups against the cylinder

You may want to check if they are there

 

[Boaf 32]

I recall you saying you replaced the master cyl... Is it a teq unit or no name? What is its part number? So I can check if you have the right master...

Did you happen to check if you had the residual valves inside?

Under the plug (where the line attaches to the master) if you unscrew that you should have a washer between the plug and master and against the plug is the residual valve then under/in that will be a spring

The residual valve keeps a slight amount of pressure to hold the drum cylinder cups against the cylinder

You may want to check if they are there

Hey JohnnyC,

It was a unit from RockAuto (A-1 CARDONE 111722 {#4720160010} Reman. w/o Reservoir). It was identical to the one I removed. I transferred the cups and two large connectors underneath. See attached installed unit.

I am not sure what the residual valves even look like (sorry rookie on Master Cylinders) but your description helps. Do you also have a photo?

The cups are held in place by large screws and a brass washer inside the cups. There is a Bleed Screw (brass I believe) on the opposite side of the brake line connections. Under the Master, are the two (2) electrical connectors. Guess they detect unbalanced brake pressure. Are these the residual valves?

Attached a Rock Auto photo. Yellow are for the cups, green for the lines, and the "bleed" screw is opposite the Brake Lines.

Thanks,

Boaf

 

[JohnnyC]

see post #4 in this thread:
QUESTION does the 76-80 disc brake master have residual valve in the front disc line

 

[Boaf 32]

see post #4 in this thread:
QUESTION does the 76-80 disc brake master have residual valve in the front disc line

Ahh, so these are under the Brake Line connections. I never took those off before installation. I thought since the Master was sealed with Plugs, it included these valves. Just heard back from Good old Rock Auto, and Cardone does not include Proportioning valves in rebuilt units.

So, called Specter Off Road, according to SOR, Proportioning Valves were not included in drum brakes (which I have on my 72). They did not appear until 75, that is in line with the Thread above. That said, Still struggling with brakes, will bleed them one last time (confirmed my spacing and clearances you highlighted earlier) before turning over to the local yocal mechanic. I'm troubled I cannot figure this out!.

Boaf

 

[tlc762]

$OR said PROPORTIONING VALVES were not included with drum brakes. What you are looking for are residual vales. Prop. valves are different from residual valves which are inside the master cylinder to maintain line pressure to the wheel cylinders. The prop. valve mounts downstream from the master cylinder in the rear line to balance front to rear brake bias-usually attached to the lower master cylinder mounting bolts.
HTH,
Will

 

[lostmarbles]

Hey JohnnyC,

It was a unit from RockAuto (A-1 CARDONE 111722 {#4720160010} Reman. w/o Reservoir). It was identical to the one I removed. I transferred the cups and two large connectors underneath. See attached installed unit.

I am not sure what the residual valves even look like (sorry rookie on Master Cylinders) but your description helps. Do you also have a photo?

The cups are held in place by large screws and a brass washer inside the cups. There is a Bleed Screw (brass I believe) on the opposite side of the brake line connections. Under the Master, are the two (2) electrical connectors. Guess they detect unbalanced brake pressure. Are these the residual valves?

Attached a Rock Auto photo. Yellow are for the cups, green for the lines, and the "bleed" screw is opposite the Brake Lines.

Thanks,

Boaf

Bleed screw?

This worries me a bit... I don't know of any bleed screws on our brake master cylinders.

There is however a screw (with a copper sealing washer under its head) that is used to keep the front piston assembly in the correct position in the bore. This screw must only ever be inserted/removed when the rear piston has been pushed fully forward otherwise internal damage will be done.

Here's that screw on my brake master just to clarify what I'm talking about...

If that screw is refitted when the pistons are "at rest" (that is, not "pushed forward") it will interfere with (and damage) the front piston (and its seals).

Just a warning... (which may be completely unnecessary because I may just be misunderstanding you).

 

[JohnnyC]

Tom ... Great point about that screw ... Thought he was talking about a bleeder ... But if that got pulled out that would explain a lot

 

[Boaf 32]

Bleed screw?

This worries me a bit... I don't know of any bleed screws on our brake master cylinders.

There is however a screw (with a copper sealing washer under its head) that is used to keep the front piston assembly in the correct position in the bore. This screw must only ever be inserted/removed when the rear piston has been pushed fully forward otherwise internal damage will be done.

Here's that screw on my brake master just to clarify what I'm talking about...
View attachment 1203070

If that screw is refitted when the pistons are "at rest" (that is, not "pushed forward") the front seal on the front piston will rip into it (and get destroyed in the process) on the very first pedal-push.

Just a warning... (which may be completely unnecessary because I may just be misunderstanding you).

So I never completely removed that screw (that I recall in my brake woes).

 

[Boaf 32]

$OR said PROPORTIONING VALVES were not included with drum brakes. What you are looking for are residual vales. Prop. valves are different from residual valves which are inside the master cylinder to maintain line pressure to the wheel cylinders. The prop. valve mounts downstream from the master cylinder in the rear line to balance front to rear brake bias-usually attached to the lower master cylinder mounting bolts.
HTH,
Will

Thanks, OK so the residual valves live inside the master cylinder, and they come with the new MC, correct? To me, that actually makes sense about keeping the pressure on the wheel cylinders. I noted earlier that when I pressed the brakes with the drums off, the Wheel Cylinders did not react until the brake was half way down in travel. That happens before and after the new Master was installed.

Still, that leaves me with...I do not have the brakes that work. Do these residual valves have ways of testing them?

Boaf

 

[calponte]

Take a air gun and take lines off at masters and blow the lines out?

 

[Fast Eddy]

Bleeding:
Reverse bled starting at the Right Rear, then moved to the Left Rear. Then to the Right Front Front, then Right Front Back. Moved to the Left Front Front, then Left Front Back.

This order is wrong for a LHD vehicle. You bleed the longest first (LR), then the next longest (RR), then LF, then RF, since it's closest to the distibution block at the front axle.

 

[sggoat]

If you are still having the pedal go to the floor when you step on it(regardless of whether the engine is running or not) and there are NO leaks on the ground--the master is bad, period.
Even if you have air in the system, the pedal will go down until the air is compressed to the max and then it will stop-and yes, it will 'feel' a little mushy, but it WILL get to the point where you cannot compress it any further--how far depends on whether your leg muscles are like mine or like the Hulk's.
(most tractor/trailers run air brakes---)