brakes sticking

[laniadude]

I have a 74 620 and when I come to a stop and release the brakes, the brakes are still slightly applied... enough that if I was downhill at a stop I can let the pedal go and the truck wont roll down... any help?

[datsunaholic]

1) Leaking wheel cylinders make the shoes swell, and get saturated in brake fluid, which can make them sticky.

 

2) Improperly adjusted brakes will stick, especially loose ones (they have to be manually adjusted every 2000-3000 miles for light wear, sooner for lots of stop and go)

 

3) A missing or broken brake spring will cause them to not retract, or only will retract by backing up

 

4) Improperly installed shoes will grab in one direction (it's not uncommon to see front brakes installed upside-down on these)

[ggzilla]

Yes, the logical place to start troubleshooting this is at the wheels. Remove the brake drums and inspect. You may find gooey stick mess or a loose part falling out. When you jack up the wheel, rotate the tire by hand. The one that won't rotate is the bad one...

[datsunfreak]

FWIW, I had this same problem on my '75 B210 and after checking everything at the wheels multiple times, it turned out to be a defective spring on the pedal itself.

 

Easy way to check is to see if (while driving) you can put your foot under the brake pedal and pull up as hard as you can. Does the problem go away then?

[laniadude]

Ok... thanks for replies... so I checked the wheel cylinders and as I thought they weren't leaking... but on that note... I had them replaced when the right front and left rear were leaking... but didn't change the shoes as well because the mechanic said they were still seevicable... could it be that they were saturated and plumped up? My pedal spring is fine... on thing I did notice is that the master reservoir caps have all the rubber torn and worn... could that cause the sticky ness... I will be replacing all the brake hardware this weekend... hopefully it'll fix it... thanks guys...

[ggzilla]

none of that explains the problem. Why replace the brake hardware? Better that you find the problem and fix it. When you jack up each wheel, and apply the brakes, does one wheel become difficult to turn? Are they adjust correctly? You should be able to spin the tire with one hand.

[VintageRice]

I have this same problem with my 70 510 and was about to start a thread.

 

Question. Is it the front brakes sticking or the rear? or all 4?

 

I just did a 280zx brake upgrade. Rebuilt the calipers(thought that might fix the problem but didn't) and installed new soft lines in front.

 

My fronts are all that get tight and stay tight. enough to where my car will stop when brakes arent applied and it makes the motor work really hard.

 

My next plan of attack is to service/replace the master cyl. Thats all I can think of.

[hawaii_620]

My rear drums were like that on my 75' 620. I rebuilt the back drums. New cylinders, new shoes and springs, new drums. Made sure I had some brake grease on the parts that make metal/metal contact on the back plate. A short while after doing the brakes, it started to "lock up" like your brakes do now. I readjusted the shoes and everything works fine, at least for now anyways.

 

I've read that it's easy to mistake the brake shoes and get the wrong one on the front/back. I couldn't tell if my shoes where on correct or not. They look the same. Is there any markings on the shoes?

[john510]

I have this same problem with my 70 510 and was about to start a thread.

 

Question. Is it the front brakes sticking or the rear? or all 4?

 

I just did a 280zx brake upgrade. Rebuilt the calipers(thought that might fix the problem but didn't) and installed new soft lines in front.

 

My fronts are all that get tight and stay tight. enough to where my car will stop when brakes arent applied and it makes the motor work really hard.

 

My next plan of attack is to service/replace the master cyl. Thats all I can think of.

Did you try and adjust the brake pedal at the master cylinder ? after doing a complete brake job my fronts were kind of tight and after driving it they would get tighter.I loosened up the pedal a bit and its fine.

[Sinnful]

I had this problem on a toyota 4runner I was working on a while back.

 

Replaced the front calipers....didn't fix it

 

Inspected the rear brakes....everything seemed good

 

And then took a gamble and I replaced the master cylinder and bam it worked. The master cylinder went bad and was not releasing the pressure so they brakes were always applied.

 

So maybe try that?

[ggzilla]

It could be a bad master cylinder. Or something else.

 

Getting the trailing and leading shoes mixed up will not cause this problem. It many cars it causes the brakes to be less efficient (but not stick). In the Datsuns I've worked on there is not much if any difference between leading and trailing brake shoes, so it won't do anything.

[VintageRice]

Did you try and adjust the brake pedal at the master cylinder ? after doing a complete brake job my fronts were kind of tight and after driving it they would get tighter.I loosened up the pedal a bit and its fine.

 

 

Interesting, I didn't know there was such an adjustment. I'll check that for sure. At any rate I'm currently in the market for a 280zx master cyl.

[BOZO]

I am at this moment working on replacing all my shoes just because of this grabbing problem and after looking over my old shoes still mounted on my truck and comparing it to the repair manual, it seems the previous owner had gotten the front left side on backwards. It is easily done. When the shoes are on properly, the edge of the brake material should be approx. 2 5/8" not 3/4' from the edge of the piston. This is if the repair manual got it right, of course.

[datzenmike]

Interesting, I didn't know there was such an adjustment. I'll check that for sure. At any rate I'm currently in the market for a 280zx master cyl.

 

Look at the peddle. There is a push rod attached to it that goes through the fire wall. Remove the pin clip and slide the clevis pin sideways and out. Now the lock nut can be loosened and the rod lengthened or shortened by turning it. MAKE DAMN SURE YOU PUT THE PIN BACK IN AND INSTALL THE CLIP PROPERLY

You should have about 1/16" of play on the peddle before the rod contacts the inside of the master and becomes firmer.

 

 

When the brake is released the internal pressure in the lines and the springs inside the master should push the pistons in the master back to their rest position and any trapped pressure vents into the reservoir. The pistons in the master could be sticking and not releasing the pressure also.

[Uncle Laulau]

I've got sticking brakes in my 72 pu. Started off noticing r front locking up the first time I applied the brakes. That went away and now I'm noticing sticking at stops. Im going to inspect the pedal, master cylinder, and brakes in that order. Thanks for the informative posts, and I'll let everyone know how it goes. Ive got my money on the r front being broken. I remember hearing a clunk when I broke way back. The clunk is gone and now the sticking.

[Uncle Laulau]

ok status thus far...1st pedal looked good. 2nd master cylinder was at min fluid mark, no visible leaking. 3rd L front wheel moderately hard to spin, and seemed our of round. 4th I turned adjusting wheel L front up 1cm. wheel spun free. Now Im gonna drive around a bit, brakes don't fail me now! oh i topped off brake fluid

[Uncle Laulau]

Arrgggg. Brakes felt a bit less firm, more normal to me. Still binds after stopping. L rear locks on hard braking, normal for pickup? I guess it's time for a brake job, yuck. I'll inspect each brake before I replace pads. Maybe I've got a loose spring? Any tips would be appreciated Thanks Uncle Laulau