Brakes won't pump up whole bleeding.

[1lo620]

So I go to bleed the brakes on my 79 620. As I bleed the brakes I just can't get any pedal. They just won't pump up. I can hear some air as I pump the brakes. I am thinking master cylinder took a dump. Or maybe brake booster. Or am I just missing something. I have bleed brakes before and no issues. So I am a bit lost here. Any help or direction would help..Thanks

[datzenmike]

Brake booster has no connection to bleeding the brakes. All it does is make pushing the pedal easier (when engine is running)

 

 

 

Loosen the e brake  some.

Back the rear wheel adjusters off some.

 

Is this a replacement master? Or has it run dry? Have you 'bench bled' it first?  front then rear fitting?

 

Did you bleed the front fitting on the N.L.S.V. before doing the fronts? then the rears? then the N.L.S.V. rear then the center fitting?

 

 

[1lo620]

6 minutes ago, datzenmike said:

Brake booster has no connection to bleeding the brakes. All it does is make pushing the pedal easier (when engine is running)

 

 

 

Loosen the e brake  some.

Back the rear wheel adjusters off some.

 

Is this a replacement master? Or has it run dry? Have you 'bench bled' it first?  front then rear fitting?

 

Did you bleed the front fitting on the N.L.S.V. before doing the fronts? then the rears? then the N.L.S.V. rear then the center fitting?

 

 

I am not familiar with the NLSV. This is the first 620 I have had that has had one. How do I bleed that out. 

And it just went dry as I changed the engine. I bleed the brakes left rear to front. Just can't get them to pump up. So if you can explain how to bleed the NLSV..that may be What the issue is. Thanks Mike you aways seem to have the answers..👍

[datzenmike]

Suddenly going dry is not normal, even when changing an engine. See if there is a pinched line that's leaking.

 

 

The '78 factory service manual says to bleed the front then the rear master cylinder bleeders first. On engine side. What I do is place vinyl tubing over the ends and into a container otherwise it will shoot all over the manifolds.

 

Then the front fitting on the NLSV. It's on the inside of frame under passenger seat.

 

Then the front wheels (disc )

 

Then the rears... left (driver's) side first

 

Then the rear fitting on the NLSV

 

Then the middle fitting on the NLSV

 

 

Have a helper pump the pedal 2-3 times and hold while you loosen any bleeder to let the air escape then tighten and tell the helper to let the pedal up. Well... you know all the rest.

[1lo620]

Ok Mike, I did all the bleeding as stated. And I still can't get a solid pedal. Nothing I see is leeking..I just don't know what I am missing?

[thisismatt]

Have you verified it's not leaking into the cab, or into the booster?  You are losing fluid, though?

[1lo620]

18 minutes ago, thisismatt said:

Have you verified it's not leaking into the cab, or into the booster?  You are losing fluid, though?

I haven't seen any fluid in the cab. And not sure if there is any in the booster. Don't seem to be looking any fluid out of the reservoir. I am going to replace the master cylinder. It is old and they aren't that expensive. But then get to bleed brakes again how fun. 

[datzenmike]

Are the reservoirs going down? This will tell you it's going somewhere.

 

 

1/ Is there a small amount of play in the brake pedal before firmness. Push with thumb, pedal should move easily for 1/16" to 1/8". This is important.

 

2/ Did any fluid pump out the master? when you bled it ???????? Important!!!!

[1lo620]

8 minutes ago, datzenmike said:

Are the reservoirs going down? This will tell you it's going somewhere.

 

 

1/ Is there a small amount of play in the brake pedal before firmness. Push with thumb, pedal should move easily for 1/16" to 1/8". This is important.

 

2/ Did any fluid pump out the master? when you bled it ???????? Important!!!!

Yes they bled out fune. Fluid went down came the bleeder fine. Don't seem to be loosing fluid now. I have a small amount of play in the pedal. I did drive around the block a few times. But I sure wouldn't drive it on the open road or freeway as it is now. 

[1lo620]

Just now, 1lo620 said:

Yes they bled out fune. Fluid went down came the bleeder fine. Don't seem to be loosing fluid now. I have a small amount of play in the pedal. I did drive around the block a few times. But I sure wouldn't drive it on the open road or freeway as it is now. 

Yes I lost a little fluid when I bled master cylinder. Not a bunch but a little 

[datzenmike]

Well you should get a good solid squirt as the entire master piston volume should push out there.

 

Do you have some small pedal play?

[1lo620]

4 hours ago, datzenmike said:

Well you should get a good solid squirt as the entire master piston volume should push out there.

 

Do you have some small pedal play?

I am getting good squirt of fluid as I bleed. And I have very little peddle. Almost goes to the floor. I don't see any leaking and the wheel cylinders are new in the rear. I am going to play around with it some more. Maybe bleed the NLSV again. 

[datzenmike]

This would indicate to me that the master is actually pushing fluid out into the lines.

 

For a faster turn around I sometimes take the bleeder out and put my finger over the hole. If there is any air or fluid pressure it will push my finger out of the way and drain. Finger covers the hole as soon as it ends keeping air from getting in acting like a one way valve. The operator can just keep pumping because you don't need to loosen and tighten anything.