Brake problems after MC rebuild

[Pdxdeli]

So I rebuilt my master cylinder yesterday and replaced my rear drum shoes, hats and wheel cylinders. Was having problems bleeding the rears with endless/consistant large streams of bubbles. I noticed the bleeder seemed lose for 1/3 of a turn so I put some grease on the thread and the bubbles seemed to stop. Fronts bled no problem. Problem is going for a drive the pedal is still spongy. Not getting much brakes until I push a few inches on the pedal. And now Im hearing a hissing/air leak sound when I pump the brakes up. Sound only occurs when the engine is running. Van is idling/driving normal so i dont think there is a vacuum leak. The master doesnt look to be leaking anywhere and I bench bled it in the van. It sounds mostly like its coming back towards the booster? Ive tried everything I could think of and am stumped.


For what its worth I read @Growlerbearnz say its typical to not get much fluid from the proportioning valve when bleeding and I didnt get a drop. Took the bleeder out and it was bone dry on the inside.

Any thoughts? I did the 3 booster tests in the manual and all seemed just fine so I figured the booster was good to go.

 

[Growlerbearnz]

Did you adjust the handbrake cable as per the workshop manual and then reset the automatic adjusters on the rear brake shoes? You have to pull the handbrake lever like 50 times (not a typo) to wind the adjusters out, and that's presuming their threads are clean and greased and turn easily.
If you haven't reset the adjusters and handbrake cable you'll get a lot of pedal movement before the shoes touch the drums.

To check that the shoes are adjusted correctly, lift the rear wheels off the ground and turn them with the handbrake off. They should turn with no drag. Now apply the handbrake to the second notch. When you turn the wheels you should feel slight drag. If you don't feel any drag until the handbrake is on the 3rd or more notches, the rear shoes haven't finished adjusting themselves: apply and release the handbrake lever a bunch more times to adjust the shoes some more.

 

[Pdxdeli]

I didnt see the parking lever adjustment. Had a hard time figuring when the shoes were contacting the hats. I backed the adjuster off most the way and still felt some drag so I left it there. I did clean and add anti seize to the adjusters so they move smoothly at least. So I loosened the cable and pulled at least a hundred times until I got too around 7 clicks once tightened back up. Pedal impoved a bit, but still has a soft spot to start. I rebled probably 5 times today and Im confident theres no air pockets floating around. (except that damn proportioning valve.)

 

[Growlerbearnz]

Section 36 (Praking Brake) has the adjustment procedure for the park brake, but here's the main thing you're trying to achieve, 0-1.3mm clearance between the plastic stopper pad and the brake backplate when the handbrake is off. (Basically the handbrake cable should always be under some tension, even when the handbrake is off):



Adjustment is at the handbrake lever, but if the cable's stretched too far you can adjust at the axle end too:

 

[Growlerbearnz]

Is this a diesel? A vacuum leak won't cause the engine to run badly, but it also won't cause a soft brake pedal. If anything a lack of vacuum will make the booster weaker, which makes the brake pedal harder (less assistance from the booster).

The brake booster normally makes a whooshing/breathing/air noise while the pedal is moving. It shouldn't make any noise if the pedal is stationary (in any position). It's possible you're just noticing it because you're bleeding the brakes and paying attention?

Have your rear shoes bedded in yet? Whenever I fit new brake pads or shoes there's always a period where I have to push the pedal a bit harder than usual (which can feel like a soft pedal) until the shoes break in. Maybe pull the drums off and see if the shoes are making full contact with the drums, or if they're only touching in a couple of spots. Shoes that aren't broken in yet will also show up as a weak handbrake.

You de-greased the brake drums before installing them, right?

If everything's adjusted right, and the handbrake works fine, there might be a problem with your master cylinder rebuild. Something assembled out of order, or installed backwards, or damaged, but I'd make sure the rear shoes are properly bedded in before pulling the M/C again.

To check for an internal M/C leak, pump the brake pedal (engine off) until all the vacuum boost is gone (the pedal will be hard), then press on the pedal and hold it. It shouldn't sink, even if you hold pedal pressure for 5 minutes.
Now, while still holding the pedal, start the engine. The pedal should drop a bit (this confirms that the booster is working).

 

[Pdxdeli]

Ok I adjusted the stopper to be around off the plate about a millimeter. but Im not seeing what pumping the brake is adjusting? When I pull the hand brake it pulls the tab away from the star wheel while moving the shoes out. I feel resistance by the 3rd click on the hand brake.

Ya I put the instrument cluster back in and it signifcantly decreased the noise. I guess its been there the whole time. Booster test looks good.

Shoes probably havent been bed in. My first go at drum brakes so Ill take it out tomorrow and do a higher speed break in period. Looks to be about 2/3 contact on the shoes currently.

New drums were de-greased as well as the whole inner drum area from old leaky cylinder before re-assembly.

The only thing I could see having gone wrong on the rebuilt was if the stopper bolt wasnt properly engaged. I fully engaged the pistons since the manual didnt mention otherwise.

Pedal pumped up and held pressure then dropped a little when the engine started.