need new drums.... sigh....

[Eomund]

Well, after diagnosing, and fixing brake problems for a while now, I've found my problem. My drums are beyond worn out.

 

Basically I've been having issue with the,auto adjusters, the pads either dragging or having,too much play and several other little issues that I was chasing.

 

Today it , came to a head. One oof the pistons was pushed out of the wheel cylinder... Which should not be possible. I've been working on cars for 14+ years (god that makes me sound old), and some real bangers too. But I've never seen drums so worn the,wheel cylinders could push a piston out.

 

I've located a store I can buy new drums for not a bad price (Rock auto has them). Unfortunately have,to wait till after Christmas. Not an informative post... Just venting.

 

And before,anyone asks, me and the arthritic ol geisha are fine and un damaged.

 

Silver lining, I found out what my problem is right?

[wayno]

It's good to hear you and your ride are all right. 

 

I would just spend the money and convert over to front disc brakes, but that is just the way I think, I got real tired of doing counter clockwise spins when I slammed on the brakes.

It seems like if the brake shoes were properly adjusted, the piston could not get out of the wheel cylinder, so it seems real strange that it could happen, did you have to pump the brake pedal every time you wanted to stop?

[Eomund]

No, they were blead properly, so thats not the case there. Everything is just too loose and jiggly. The binding, I had thought was from debris in the line or something, turns out something was just cocking or something due to being loose and all.

 

I will order new drums and pads for,all 4 corners. I have new wheel cylinders for the front already that need to be installed. I will probalbly replace the rear cylinders.... Again... Just for good measure. After this, everything will be new in the brakes.

 

Unfortunately the disc conversion is out of my price range. I'd love to do it, but the kits I've seen cost more than I paid for the truck. More than I can swing right now.

[Eomund]

Oh, and to add, all my problems oddly have been with the rear breaks. When I get the time and money, Im prolly going to convert to dual reservoirs up front. Thinking of using the hardware from a Z.

[Eomund]

I did want to check if anyone's had any issues like this before.

 

My reasoning is , everything seemed way more loose than tolerances,should be. However, all the bolts and everything are tight, and none of the hardware is loose. Im 90% sure this is my problem, just looking for confirmation.

[wayno]

The way I see it, if the shoes are adjusted properly and the shoes are mounted properly, there is no way for the piston to get out of the wheel cylinder, it just could not move that far, as the shoe would hit the drum first, now if the shoe adjustment is maxed out to where there is no adjustment left, that possibly could cause an issue, but I believe that it is not possible to max it out, as no matter how warn the drum is, there just isn't enough room in there to have that happen.

When you adjust your brakes, you adjust them till the wheel won't turn anymore, then back it off till it just rubs on the drum a little, correct?

[DanielC]

A stock Datsun 521, with correctly adjusted drum, brakes, that are bled correctly, should have the brake pedal higher than the gas pedal, on a hard stop.  If you set the hand brake, the foot brake will have much less travel, unless there is air in the rear wheel cylinders.

 

You cannot bleed the brakes on a 521 with a pressure bleeder.  One of the quirks of a 521 is there is only one port on the wheel cylinders.  a lost of other cars, and trucks have two ports into the wheel cylinders, and the bleeder fitting in on the highest port.

To get all the air out of the wheel cylinders, you have to let the brake shoe springs return the slave cylinder to the resting position.  That  allows any air in the cylinder to travel backwards to, and out of, the bleeder fitting.  If you close the bleeder fitting, when there is still pressure in the system, the air remains in the slave cylinder.

 

The adjuster barrel should be able to slide on the brake backing plate.   Not easily move, but slide with some difficulty.  If the adjuster on one side slides easier than the other side, the brakes on the easy side will tend to lock up easier

 

The Factory service manual recommends adjusting 521 brakes every 3000 miles.  if you do a brake job on a 521, you need to adjust the brakes much more often, until the shoes wear to the exact diameter of the drum.  Then you can go with 3000 mile adjustment intervals.  do a panic stop in a safe area after adjusting the brakes.  If the truck pulls to one side or the other, you can adjust the side it pulls to a little looser, or tighten up the other side a click or two tighter.  Sometimes driving slowly, riding the brake pedal will even out the brakes.

[datsunaholic]

 

Basically I've been having issue with the,auto adjusters, the pads either dragging or having,too much play and several other little issues that I was chasing.

 

 

521s don't have auto adjusters.  You have to manually adjust them, usually every oil change.

 

I've never had a piston pop out, but it is possible, especially if the lining has come off or the shoes are put on backwards (yes, they're directional).

[dat521gatherer]

There are no auto adjusters on any of the 4 brakes if they are stock.

 

When I had my drums turned last the machinist didn't go in far enough so the edge of the shoe was riding on a inner lip of the drum thus not making full contact. Just thought I'd throw that out there.

 

Also most adjusters on 521's seize up and need to be taken apart and cleaned throughly. After everything is working right make sure your 4 dust boots on the back of the adjusters are there doing there job keepind rocks and water out.

[wayno]

Both of you above read better than I do I guess, I should have caught that auto adjuster thing, the trucks didn't have auto adjust capability till somewhere around 1985.

You have to adjust 521 brakes manually Eomund, you turn the adjuster till the wheel will not turn anymore, then you back off the adjuster till you can spin the wheel almost a full turn before  it stops, do all 4 wheels this way, if you cannot turn the adjuster when you have the brakes apart, then pull it off and get it apart, clean it up, lube it, put it back in and put it all back together, note which way the adjuster wheel needs to turn to tighten it, tighten it to the point that you can just get the drum on, then move to the next wheel.

When all 4 wheels are done, then bleed the brakes, start at the farthest point away from the master brake cylinder, and work your way to the closest from drum, then after that is done, adjust all the brakes like I mentioned above.

[Eomund]

Hrmmmmmmm..... Okay, something to look into then. Very, very likely to be the issue.

 

I'll look at it tomorrow. Good,to know you almost always have to check it as well.

[kelowg]

Also when adj shoes, after u get them to your liking. Spin the wheel and apply brakes a couple times. Most likely they well b loose again so readjust. The adjusters slide around a bit during braking and change things.

 

Dragging brakes, can b caused by lack of lube on all contact/pivot points.

 

Front disc conversion can b done for less than 500.00 with jy parts.

[Eomund]

You guys seem to hit the nail on the head. The more I read, the more this definately holds water. Christ, how could I not notice it was a manual adjustment? This is the oldest car I've ever owned, never seen one manually adjusted before save a motorcycle.

 

Thanks so much for the input. I'll update when I get it looked at (might not be today if it rains :( )

[datzenmike]

wayno... auto adjusters were introduced Dec. '82 on the 720 trucks. This also the advent of the Z24 and the increased size of the 720 front calipers. If this 521 has self adjusters then some serious swapping of parts has been going on.

 

I've seen many non Nissan brake set ups where there are stops so the piston cannot possibly push out of the bore. The 720 doesn't appear to have this so neither would the 521, but either way the piston can only pop out if the brakes are applied with the drum off.

[Eomund]

wayno... auto adjusters were introduced Dec. '82 on the 720 trucks. This also the advent of the Z24 and the increased size of the 720 front calipers. If this 521 has self adjusters then some serious swapping of parts has been going on.

 

I've seen many non Nissan brake set ups where there are stops so the piston cannot possibly push out of the bore. The 720 doesn't appear to have this so neither would the 521, but either way the piston can only pop out if the brakes are applied with the drum off.

Lol, tell that to my brakes

[datzenmike]

Yes.

 

This is why I say some things must be not original parts. Maybe just the shoes are worn out? Can you post a picture?

 

Normally brakes have lots of redundancy or 'over build' in them. Well worn shoes and drum should not be the cause of the cylinder pistons popping out and the total loss of hydraulic pressure. I believe the 521 has a single master??? This would cause a massive and total loss of all hydraulic braking

[Eomund]

Yup, single resivoir master, and yes, the brakes go out. The shoes aren't that old. And everything per the microphich and pictures are OEM. Think everyone else hit it right that it's just way outta wack in adjustment. I'll get some pictures when I work on it today.

[DanielC]

The brake drum inside diameter is 10 inches.  .040 is the wear limit.  I take brake drums to a auto parts store, that does have a machine shop, and have them measure the drums. 

 

Just in case it is not clear, the brakes on a stock 521 are NOT self adjusting.  You have to adjust them.   A lot, especially right after working on the brakes.   Backing up and stepping on the brakes DOES NOT adjust them.

 

To adjust the brakes, you have to block the truck so it cannot roll.   The truck must be in neutral for the rear brakes, and the hand brake must be off.   Then you jack up each wheel, until it is off the ground.  There is an oval dust cover on the bottom of the backing plate, remove it.  You need a narrow (1/4) spoon, or screwdriver to reach the adjuster.  If the brakes were assembled correctly, you turn the star wheel adjuster down to spread the shoes.  If you have the brakes apart, the adjuster assembly for the LEFT side has LEFT hand threads.

 

You adjust the star wheel tighter until you cannot rotate the wheel and tire forward and back. The brakes are self energizing, it will be easier to turn the tire backwards.   With the brake adjustment tight, step on the brake pedal, fairly hard.  If you can turn the tire and wheel by hand after stepping on the brake pedal, tighten up the star wheel some more.  Then, according to the FSM, you back off the star wheel 12 clicks.  If your drums are good you might be able to back off 9 or so clicks, but make sure the brakes do not drag.  A very light scraping sound is OK, but it should not noticeably drag the wheel and tire.

 

For the front wheels, turning the steering wheel hard right, makes the right brake adjuster easier to get to.  Turn hard left for the left wheel.  a straight screwdriver will reach the star wheel easily. 

For the rear wheels, there is no easy way to reach the adjuster.  I have a small pry bar, with about a 1. or 1 1/2 inch radius in it right at the end, that will reach the rear adjuster, and clear the rear axle parts.  For me the easiest way to reach the rear adjuster, after jacking up the truck rear wheel, is to crawl under the truck, just in front of the rear wheel, and get to the back of the brakes that way.  MAKE SURE THE TRUCK IS SECURELY BLOCKED, SO IT CANNOT ROLL.  If you are adjusting the rear brakes you cannot have the hand brake on.

 

When done, put the dust cover back on.    I was able to get new adjuster dust covers from a local Nissan dealer, when I need some, a few years ago.

[datzenmike]

A picture would help but what you think is an auto adjuster simply shouldn't be there.

 

521

 

720 would look like these with a cable self adjusteradjuster

 

 

 

 
This looks pretty close to a Nissan automatic brake adjuster. The start wheel is threaded and moves outward to spread the brake shoes to adjust for lining wear. The metal plate above it is worked by brake action and levers the star wheel out. When the shoe travels too far, the lever catches one of the teeth on the star wheel and ratchets it out.

[wayno]

I believe it is possible to transfer 1983+ everything from the backing plate to the drum onto a 521 rearend to upgrade to automatic adjusting rear brakes, but I don't know it, but it looks possible to me.

But the only reason I actually could see a reason for doing this is brake part availability, which is really not an issue right now, so I don't see the point, as the rear brakes hardly ever need adjusting anyway.

 

It's been so long since I looked at a 720 rear brake assembly that was built after 1982 that I have forgotten what year they started the automatic adjusters, I have two rearends in vehicles made after 1982, the 520 is one of them, but I hardly drive it, so the rear drums have not been looked at since I put the frame to use and bled everything, the other one is the work truck, that is a dually rearend, and it is different, but it does have automatic adjusters.

 

 

[Eomund]

Ya it's not an auto adjuster.

 

So final diagnosis, now that I've had it apart.

The adjustment was way off.,enough,that it pushed the,cylinders far enough that it damaged on of the seals. It also pushed the cap that sits on the piston off due to its looseness.which was the audible clunk I heard.

 

I need a new wheel cylinder now, and have one ordered. I'm still getting new drums after christmas, just cause I can.

[Eomund]

So final update to this. Got everything together a couple of days ago, and now,adjusted correctly. Ive pulled it apart twice to verify again that everything was good (gladly it's all correct and staying that way).

 

Adjusting these brakes are fiddly as hell.

[wayno]

Adjusting the brakes is easy if you can figure out which way to turn the adjustment wheel from the back access hole, I always have trouble remembering myself.

What I do is get a light that I can aim at the hole while I am under the truck, I pull the plug off after I know which way to turn the adjustment wheel, aim the light threw the hole so I can see the teeth on the adjustment wheel, then I use an appropriate screwdriver and turn the wheel the correct direction till I cannot turn/spin the wheel/tire, then I back it off(the adjustment wheel) till the tire/wheel will not quite spin a full revolution when I spin it, you will hear the shoes scraping on the drum, but as long as the wheel will spin a little, it will break in without over heating the brakes.

[Charlie69]

If your backing plates are clean, or clean them, take a paint pen and draw an arrow in the direction you need to turn each adjuster.  This helps me adjust the brakes faster.

[wayno]

If your backing plates are clean, or clean them, take a paint pen and draw an arrow in the direction you need to turn each adjuster.  This helps me adjust the brakes faster.

 

This is a great idea, but then I would get confused on if that is the way the wheel is supposed to turn, or  that was the way the screwdriver was supposed to move. :lol:

It's always going to be something with me, isn't it. :lol: