Spongy brakes

[MiltonV]

Hello, so this is what happened, the truck was braking perfectly but I had to remove the rear left plate where the brake pads and all related hardware goes to fix a small defect in the adjuster channel, I removed the wheel cylinder and after assembling everything and bleeding brakes now efficiency is about %50 I bled it twice and no air bubbles comes from it but still doesn't work as it used to, so, any ideas?

[thisismatt]

You posted in the 620 forum, but list a 521.  What vehicle is it?

[MiltonV]

620 truck I have both

[thisismatt]

2 minutes ago, MiltonV said:

620 truck I have both

Depending on the year, you may have the nissan load sensing valve (NLSV).  Look at the inside of the passenger frame rail near the seat area.    Bleed order is: 

 

NLSV front bleeder

Front wheel cylinders

Rear wheels, left first

NLSV rear bleeder

NLSV center bleeder

[MiltonV]

No NSLV It goes direct from Master to a brass cube where it splits to  both front disc and the other circuit direct to rear wheels.

[datzenmike]

Better list what 620 you have. '78 and up were disc brake and have NLSVs.

 

Looks like '76 and up had the MLSV.

 

The disconnected brake line probably emptied and probably some air in the other rear one as well.

 

Loosen the emergency brake cables some and try. No need to bleed the fronts as they are separate from the rears.

 

What I have found useful is to disconnect the line at the wheel cylinder and put thumb over the end and hold somewhat firmly. (yes it's messy) Have someone pump the brake pedal repeatedly. Your thumb acts as a one way valve preventing air from being sucked back in. Make sure the master does not go dry. This method will move large amounts of fluid faster than a bubble can rise and remain at a high point. When only fluid comes out after multiple tries, connect to the wheel cylinder and quickly bleed it. Do the other side and don't forget to adjust the e brake.

[MiltonV]

8 hours ago, datzenmike said:

Better list what 620 you have. '78 and up were disc brake and have NLSVs.

 

Looks like '76 and up had the MLSV.

 

The disconnected brake line probably emptied and probably some air in the other rear one as well.

 

Loosen the emergency brake cables some and try. No need to bleed the fronts as they are separate from the rears.

 

What I have found useful is to disconnect the line at the wheel cylinder and put thumb over the end and hold somewhat firmly. (yes it's messy) Have someone pump the brake pedal repeatedly. Your thumb acts as a one way valve preventing air from being sucked back in. Make sure the master does not go dry. This method will move large amounts of fluid faster than a bubble can rise and remain at a high point. When only fluid comes out after multiple tries, connect to the wheel cylinder and quickly bleed it. Do the other side and don't forget to adjust the e brake.

It's a 79, 

Anyway problem solved, previous owner filled like 1/4 the slot in the hand brake link so brake pads didn't close, the adjuster was almost seized but I removed it and greased so now it moved freely, but since the pads didn't close enough when brakes were applied both tend to rotate with the drum and also affecting braking efficiency.

I compared both links with a spare I have and noted  the difference so I removed the excess material and now it works like a champ.