71 521 brake problem I think?

[Barber Phil]

I have a 71 521 with drums all around. The pedal seems to go way to far down before it stops. I am not sure if this is just the way it works with all 4 drums. this is my first vehicle with this set up. I have replaced all 4 drums, wheel cylinders, shoes. I have replaced the master cylinder twice and all of teh hard and soft brake lines. I have bleed them to many times to count and have adjusted and readjusted them. The truck does stop and will lock up all 4 wheels if you slam on the brakes but my foot will be 1/2 inch from the floor before it stops. any help would be grately appreciated.

[izzo]

Start from the top. Check your fluids, bleed the brakes. Drum brakes need adjusted! Had a car once, bled the brakes. still did it, kept bleeding them, finally some more air came out and it was done.

 

Check for leaks first.

[kelowg]

make sure u dont have too play on mc pushrod, also be sure shoe adjusted correctly.

tighten them up until u cant turn the drum, back off til just dragging.

on the front, i need to pump the brakes couple times and recheck shoe adj

[Barber Phil]

I have done all of this stuff time and time and time again I have bleed like 2 liters of fluid through them with the current parts and there are definetly no leaks. I think i have adjusted the shoes on here like 15 times. I will try it one more time tomorrow but when I adjust them I have someone pump the brakes to make sure they get adjusted right. I may try to adjust the mc pushrod out a little.

[datzenmike]

All you need to do is push down on the clutch peddle with your thump. There should be about 1/16" of peddle play before there is resistance.

[DanielC]

Did you fill the wheel cylinders with brake fluid before you put them on? The bleeder fitting does not bleed air out of the wheel cylinder itself, but out of the brake line right before it goes into the wheel cylinder.

I do not know how to get all the air out of the cylinder. I have thought that by loosening the brake shoe adjustment, and then bleeding the wheel cylinder, that would allow the wheel cylinder to move a lot, fill with fluid, and then when the bleeder fitting is opened, the brake shoe springs would then collapse the wheel cylinder, and expel the air out of the wheel cylinder, but I have never tested this theory.

 

When you bleed the brake lines, bleed the longest line first. That is the right rear, then do the left rear, right front, and finally left front.

[Barber Phil]

OK so i adjusted the mc pushrod out a little right to where there isnt any free play in the pedal only took about 1/16 of an inch. also bled again and redajusted again still the same issue. the weird part for me is the truck stops fine and the pedal never hits the floor it just seems to go really far down to get the truck to stop. when stopping there is probably only 1/2 inch left before the pedal hits the floor. However again it does not hit the floor.

[banzai510(hainz)]

adjut the brakes till its slightly rubbing then back off one maybe to clicks.

Your adjusting the start wheel back behine the hub right?

 

I bleed my system using a bottle with tube going in it. so I can see no airbubbles

[mklotz70]

It's all in the adjustment of the shoes. If the pedal feels rock solid when you push down hard, you've bled it correctly. If it feels spongy when you hold it down, there's air in the line. If it slowly drops while you're pressing hard, there's a leak. So...going by what you said....it sounds like it's rock solid, doesn't drop and is not spongy.....it's simply the shoe adjustment. The shoes are requiring too much travel before engaging.

 

With the car on stands and the wheels still on, adjust each wheel until they drag constantly....then back off a couple of clicks. Press the brake pedal to recenter the shoes and see if they drag. You'll want a bit of scuffing...probably no more than about 25% of the rotation. This should go away in a couple of days of driving and the shoes seat into the drums. When I say 25%...drums typically scuff in one spot when turning as opposed to dragging all the way around. If it drags really hard in one or two spots and not in the others, I'd take them off and have them turned....yes, even if they're brand new. Most parts stores will true up new drums or rotors for you when you buy them if you ask....but if you take them and bring them back, you'll have to pay. If the drums are "true" and perfectly round, the shoes should scuff fairly evenly all the way around. I would leave them with a slight drag...something you hear more than feel in the rotation. Don't forget to keep pushing the brake pedal down hard each time. Each time to turn the star adjuster, you can move the shoes back and forth....offsetting how they are centered....so, do a few clicks and spin the wheel, but push the pedal down hard before you trust what you hear or feel.

 

You want to leave the tire/rim on because if you do this with just the drum, the tiniest rub will feel like it's rubbing really hard. The diameter/weight of the tire will give a much better feel of how hard it's rubbing. Also, it's good to have the drum held on with the torqued down lugnuts so that it's all nice and even.

 

You want some scuff or rub so that you know your shoes are really close. If you jack it back up after a couple of days, I'll bet they don't rub anymore. You can readjust them again....this time you'll be looking for very little to no scuffing. Reason being that you "bed" the shoes into the drums. This can take a couple of days to a week or so, depending on how much and how hard you drive it. With the initial "softness" of the shoes gone, you should be able to get them really close without needing to rub. You may notice that in the first week your pedal drops a slight bit because of the shoes seating.

 

Anyway....you've adjusted all four and have what feels/sounds like even amounts of scuffing on the new shoes......your pedal should be close to only being half way down or less if your drums are pretty true.....time to drive. I prefer to test them in dirt or gravel to save on my tires....or I do it in the rain. You're looking to see which one locks up first. This is probably much more noticeable on the front brakes. One wheel locking up on the rear is easy to tell, but it won't throw off the direction of your vehicle like one front wheel locking up. If your pedal feels good and you have one constantly locking up first, back that one off a click and try again. If you have one that doesn't lock up like the rest, tighten that one a click and try again.

 

Yes.....this is a pain in the rear....that's why everyone goes to disc brakes!!! :)

 

I ran through that kinda fast....let me know if you have any questions. :)

 

oh...you can download the factory manuals on my site www.olddatsuns.com (free) if you want to do it by the book. :)

[mklotz70]

oh...on your m/c pushrod....you don't need much play, but the rod should feel loose just to make sure you're not actually pushing the piston in :)