Sticky brakes

[1lo620]

So what would cause the brake shoes to stick when I brake, mainly only when I brake hard, I can feel them drag for a bit, and I can smell the friction. They are new brakes and brake cylinders, and when I had them apart I cleaned and lubed the adjusters.

Also pedal seems spongy, but that is probly just need to be bleed better..I guess...? Any info, out there from the Mighty Datsun Clan...thx

It is a 74 620, and yes drums all the way around, and dont tell me to get disc....I will when I am able...thx

[datzenmike]

Broken or slipped off return spring.

 

Or being new they are just 'breaking in' pun intended. They are getting hot for the first time.

[ggzilla]

Since you just changed them, I'd follow Mike's train of thought. Take the drums off and inspect.

 

If it was fine then started, and you hadn't just replaced them, most common is a slow-leak wheel cylinder. Causes the brakes to get sticky. Smells funny too.

 

 

For better bleeding put a hose from the bleeder to a clear glass with some new fluid in it, enough to cover the bottom of the hose. Crack the bleeder slightly. Have someone pump the brakes while you watch the glass. When air bubble stop coming out, it's done. The fluid prevents air from going back up into the cylinder.

 

With this method, no need to loosen/pump/hold/tighten and all that bother.

 

 

If the master cylinder ran dry when you replaced the wheel cylinder, it may need bleeding up at the master cylinder.

[mklotz70]

get discs!

 

LOL!! sorry....couldn't resist :)

 

 

I'm pretty sure if the shoes are on wrong....there's a difference between the front shoe and the back shoe....they can hang up like your saying.

 

That bleeding method can work, but the hiccup is that if it's easier for the system to suck the fluid back in from the jar, it will. You really want it to suck new fluid in from the m/c reservoir. You won't see any air come out because it will suck it back into the line when you let up on the pedal. Basically, the fluid(and air) will simply move back and forth in the line. You won't get any new air because the tube is in the jar with fluid, but you won't actually push the existing air out unless new fluid is coming in from the m/c. If the system finds it easier to pull fluid from the m/c res, then that method works great. So...I'm not saying it won't work, I'm just saying that you'll want to double check that it is working. If the fluid does not go down in the m/c res when you do it, it's simply moving fluid back and forth and you'll need to close the bleeder valve to force it to pull new fluid from the m/c.

 

I've seen a brass item on some bleeder setups in the parts stores. It goes on the end of the tube that goes in the jar. It's got a ball and spring in it. When you press on the pedal, the spring gives way and lets the fluid escape. When you let up on the pedal, the ball seals off the hole/tube and the fluid must be pulled from the m/c.

[ggzilla]

It's worked for me for years, and it does push a lot of air out -- you can see the bubbles. Takes maybe 10 pumps before the bubbles clear out, something like that. There is a little bit of the backwash you are talking about, but overall is doesn't matter. More comes out than goes back up.

 

I can also clearly see the old fluid coming out, then finally get clearer. Give it a try!

[mklotz70]

It didn't work for me, but that was many years ago when I was a kid and didn't know anything. I may have been doing something else wrong. I'm glad to hear that it works so well. The weight or resistance of the fluid in the lines should be a lot more than the resistance of the fluid being pulled in from the m/c. I will definitely try it again :)

 

hhhhmmm...now that I think about it more, I've done that to change the fluid and it's always pumped out, not just vacillated back and forth. Funny how we can get set in our thinking and go years without retrying or reconsidering things. oh well. :)

[1lo620]

I know I am not a mechanic, But I can and do know the differnence between front and rear brakes, and besides, Pumpkin Dave did the brakes....I will check and see if something popped off or see if they are just over adjusted...let ya know what I find thx guys...

[mklotz70]

I meant the actual shoes inside one drum....there's a diff between the one that goes toward the front and the one that goes toward the rear. It has to do with the drum brakes being self actuating. I certainly wasn't trying to slam on or offend either of you two Daves :) I partly pointed it out because there's a small chance it might be the prob and also because other guys reading this will be looking for options to a similar prob they're having. Anyway......with the way my luck is going, someone will come on and point out that I'm completely off base!! LOL! I'm not sure why I bother half the time anymore.

[datzenmike]

Leading and trailing shoes. On a properly fitted vehicle ever notice how it stops better going forwards than backing up?You got it right Mike... it's something to consider.

[Tice]

I agree that the new parts may still be "Breaking in". and resetting the shoes may be an idea (Back up for a bit, slam on brakes). Of course the Mikes seem to have a good point, may have wrong shoes in wrong places. Good luck!

[ggzilla]

With many Datsun there is not much difference between leading and trailing brake shoes. If you have both sides matching, I doubt you could notice a difference. Which is not the case with most cars where brake performance backing up and going forward makes a huge difference.

 

But always best to do it right. Only takes 15 minutes to check.

[dat521gatherer]

For a 10 year period I almost got rid of my 521 many times cause it wouldn't stop. Countless brake jobs(at the shop) and I kept telling everyone it stops on a dime going in reverse. As it turns out when I did my king pins years ago I put the damn whole hub/knuckle assembly's on the wrong sides so the single piston wheel cylinders were pointing the wrong way. After I noticed that from looking at my next 521 it was like winning the lottery. :hyper:

[EricJB]

You mentioned that you cleaned and lubed the adjusters. Did you clean and lube the shims and clips that mount the adjuster to the backing plate? The adjuster should slide in the slot, and center the shoes.

 

I bought a car years ago that had the small spring on the whl cyl side, and the big spring on the adjuster side. I dont even remember what kind of car it was now, but I do remember the thing drove like shit. Good luck.

[1lo620]

Ya soon as it warms up a little bit here is Seattle I am going to pull them apart. I only have a one car garage and that is where my show truck is. I am not a big fan on working on trucks in 3" on snow..So when I get them apart and check them out and I still cant figure it out.. I will let you all know...Thanks for the advice guys... I guess one of these days I will actually have to learn to work on this stufff myself...Lol...But I will say this, next major thing on this truck is Disc conversion.....