Brake bleeding secret?

[gearhead]

Is there some sort of brake bleeding secret to help bleed the brakes on a 74 620?Ive bled the brakes 5-6 times times and still my brakes suck ass.This latest time I even used a vacuum bleeder and it pulled out MASSIVE amounts of air,and still my brakes suck.I just want to be able to lock up all four tires if I panic stop.Right now it seems like I would stop better if I just dragged my boots on the ground.

 

It has a brand new master cylinder and it doesn't look like anything is leaking,but I still have tons of air in the lines.I'm getting the impression that the brake lines actually go into some alternate universe before coming back to the truck and the alternate universe is full of air because there is no way the lines on the truck could hold that much air.

 

If I open a bleeder there is fluid there,but still lots of air.If I pump the brakes after 4-5 pumps it firms up.

If I can't get it working right after the next couple tries I'll just go and get new wheel cylinders all around,even though its supposed to have them..

[Laecaon]

Did you bench bleed the MC?

 

I did a full fluid flush on my car, but there was still air trapped in the MC itself.

[Guest 510kamikazifreak]

Did you bench bleed the MC?

 

I did a full fluid flush on my car, but there was still air trapped in the MC itself.

 

This first and foremost

then bleed the brakes from the furthest point(of the master,usually rr,lr,rf,lf) working towards the closest point

[datzenmike]

First why are you bleeding them? If something was replaced, go there first and be sure all fittings are tight and not allowing air back in of leaking fluid out.

 

To bleed the master cylinder get a short length of vinyl tubing and fit over the front bleeder (marked F and located closest to the firewall) and pointing towards the driver's fender. Fill the reservoir and stick the other end into the fluid. Loosen the bleeder and pump brake until no air bubbles come out. Close bleeder and do the rear bleeder (marked R which is to the front) tighten bleeder..

 

Before bleeding raise each wheel and adjust the drum brake so that the shoes are just dragging when you spin the tire.

 

The other thing is your method. I have the '73 620 FSM and it says to bleed the rears first then fronts. Generally the one furthest from the master moving closer as you go.

 

If you have a NLSV (Nissan load sensing valve) in line on the rear brake line...look on the inside if the frame under the pass side seat. (the '74 may have it I don't know) The procedure for bleeding this system is ...

NLSV front bleeder

Both front wheel cylinders

Both rear wheels, left first

NLSV rear bleeder

NLSV center bleeder

 

Get a proper brake fitting tool.

[jesusno2]

YES! ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ mike that stupid valve! it traps air like a sonofabitch! 90percent why 620 brakes never work i always use vacuum on it 

[datzenmike]

He'll have to look to see if he has it. The '73 FSM does not mention it.

[jesusno2]

73 didnt use it i know as fact had one, but 74 or late model 74 did.

[alabama_lowlife]

I was having trouble with bleeding my 521's brakes. I read somewhere on here to adjust the shoes all the way out. Until you can't turn the wheel at all. Then bleed them. It worked for me, I just readjusted the shoes when I was done bleeding.

[gearhead]

what does that load sensing valve look like?I don't think it has one but to be sure...

[gearhead]

got it figured out,both rear lines were leaking at the fittings.