Rear brake adjusters rusted

[rjgilligan]

My 79 feels like it has some brake issues. When I press the pedal in softly, it stops the car, but then seems to lose tension. Sometimes when at a traffic light, the truck will start to roll forward again even with my foot on the brake. This happens after I used the brake to come to a complete stop. The pedal slowly sinks down until the truck starts rolling.

 

Brake fluid levels look good.

 

Is this a matter of just moving the rear brake adjusters? They are rusted and I can't budge them. Got a lead on some new ones from a Nissan parts place but they are a bit expensive (for a Datsun). 

 

Has anyone had this issue?

[laotsu]

don't bother getting new adjusters. Just refurbish the ones you have they are practically nuke-proof if you don't try to wreck them.

 

as far as the pedal creep, that doesn't sound like an adjustment problem. adjustment is more of an overall low pedal than a fading pedal.

 

it sounds like you have air in your lines and need to bleed your system. I would also recommend bench bleeding your master when you bleed to ensure that all air is out.

[datzenmike]

If the system is tight and there are no leaks then the pressure must be dropping as you sit with the brake pedal on. Only way I can see the pressure drop is fluid is leaking back into the the master reservoir.

 

As to the rusty adjusters... take them off and heat, WD-40 and vice grips will usually get them moving. Take the screw parts out and clean thoroughly and coat with anti seize compound or brake grease. Instal and adjust them out until the drum just barely rubs when turned. Make sure you put those oval black rubber plug/covers back on or shit will get in there and rust them up again. Get some if you don't have them.

[Aibast]

Do as datzenmike says - did mine the same way now they works so well that one vibrated out of adjustment. Before that it was rust covered and siezed lump of steel. If you have graphite oil use that to soak it in. Then add heat, that gets them loose. 

[pharouh]

Once again,Mike knows!

 That's what I had to do to mine.  And make sure you put them back on the same wheel. 

[rjgilligan]

Okay, thanks guys. I'll soak the adjusters. As for the pedal sinking... should I get a new master cylinder? Rebuild the one I have? The beck/arnley ones on rock auto are only 18 bucks. Why is there such a price difference between that and some of the others, which go up to 90?

[rjgilligan]

Oh, there's a wholesale closeout..... nevermind that last question.  Seems like I should jump on that.

[rjgilligan]

Well, the new master cylinder came but it looks way wrong. Can someone tell me if I should send this back or if it will work? It is different than the stock one in my 1979 620 in that it only has 1 bleeder valve on the side, and has a female threaded end. It also says 7/8 on the top.

 

Here's my current one:

 

Here's the one that just arrived:

[rjgilligan]

This thing is for a Mazda... they boxed me the wrong part.  This is troubling because I'm gonna start driving across the country in 3 days.  Not enough time!