To Bench Bleed, OR, Not To Bench Bleed

[MrMarty51]

Two different instructions from the same manufacturer, Dorman.

Heading to the vice with my old fashioned plastic bench bleeding fittings and hoses.
I do not see anything special about this new master cylinder that would make it any different than any other master cylinder that I have purchased new, or rebuilt myself.
Single piston master cylinder for the 59 Power Wagon.

 

[MrMarty51]

The instructions says to use the provided solid plastic plugs and screw them into the ports. Use a blunt instrument to depress the piston no more than an inch at a time, repeat until piston will depress no more than 1/8” at a time and no more air bubbles appear in the reservoir.
Install the master with plugs in place. Install one line at a time and lightly press pedal to bleed the junction.
No different than what I have always done except I always used the provided bench bleeder fitting/hose kit.
And the instructions is mentioning a stepped master cylinder. This one is just a straight bore unit, so, here goes.
It’ll bust or function.

 

[Will L.]

When in doubt, call their tech support.

When rolling dice:
Don’t bleed it. If you don’t bleed it and should have, you can always remove and bench bleed it later.

If you bleed it and shouldn’t have, you cannot later choose the other option.

 

[cornemuse]

Not my truck, but almost same issue,
My Mercedes, about 15-20 years ago, I replaced the master, bench bleed with plugs & hoses
Year ago replaced M.S. again. Solid plugs, (on bench) pump with blunt stick till ⅛" etc.
I allus save the old plugs tubes and instructions! 30 years worth!
Different instructions 20 years apart, , , ,

FWIW, edit: from O'Reilly's, allus have had good luck with them

 

[MrMarty51]

I bench bleeded it with the old fashioned hose kit.
I plunged the piston just enough to emit bubbles out the piston feed ports. When no more bubbles appeared in the reservoir then plunged slightly deeper, repeat until the piston was near bottom and no air emitted from the bleeder hose or the on the reservoir piston feed ports.
Guess if its wrong it warnt a terrible expensive mistake.
Buy a rebuild kit and start over.
I tried installing it lone wolf style.
Nothing doing. Could not get the master close enough to the bolts to get a nut started.

Now waiting for the son to come over.

 

[MrMarty51]

Old PW gots brakes and it stops.
The son came over and he held bolts, I started the snuts, tightened them all down, bled out the brakes. Son left and I went phor about a 30 mile drive.
Old PW runs quite nice.