Packard Forum Index » Post-War (1946-54)

Is the procedure for bleeding a treadle vac master any different than normal? Just run a line from the outlet port back to the cylinder reservoir and stroke the piston a few times?
Thanks

You're right, bleeding is no different than with a manual master cylinder, and best done with the engine not running though some extra foot pressure will be required. Accepted practice is to start with the wheel cylinder furthest from the MC.

EDIT - But I've never actually done it by running a line from the wheel cylinde outlet back to the MC; I usually have a buddy press down on the brake pedal and then open the wheel cylinder to purge the air/fluid, and make sure the WC port is closed before the pedal is allowed to rise. You can also run a tube from the WC into a jar of fluid (line below the liquid level). But in either of these methods you need to check that the MC fluid level doesn't fall too low.

EDIT - thanks guys for picking up on my error, I missed that the query was just about bleeding the master, not the system. But flushing or at least replacing brake fluid at intervals is a bit of maintenance that I think is for the most part neglected by many owners, so even if just the master was in need of bleeding, I'd be inclined to thoroughly bleed the entire system if it hadn't been done recently.

Mike. What u said is correct for MASTER cylinder regardless of power or manual or treadleVac all the same.

Owens advice is for the WHEEL cylinders and i ageree with his advice on wheel cylinders. Need an accomplace to bleed whell cylinders.

Thanks-master cylinder was what I was concerned with. I have a handly dandy vacuum bleeder that I use on wheel cylinders and calipers. Makes it a one man job.
MIkeG

You might check these out. I bought a set and it made bleeding an easy one man operation. Just need to make sure U don't run M/C too low. Also got the recovery bag which keeps it a clean operation.

russellperformance.com/mc/speed/import.shtml

The vacuum bleeders are just fine for preliminary bleeding. Just to get excess air removed to save on pedal pumping/time/labor etc. A FINAL bleed as Owen described is optimal. Usualy another quick pop of the bleeders some 200 or 300 miles later too.

The vacuum bleeders can allow some air into the cylinders around the threads of the bleeder screw.

store.motiveproducts.com/shared/StoreFro ... C&Count1=185634791&Count2=102775216

I've been using one of these power bleeders, makes it an easy one-man job. also great for flushing out the system.

I have never bled a TreadleVac master cylinder, itself.

Take a look at the cross-section shown in the Brakes section of the factory shop manual. Notice that the compensator port is open when the pedal is in the released position. My feeling is that this particular master cylinder is, for the most part, self bleeding - just fill it up and wait a little.

Now, I will admit that there could be some air trapped in the passage leading to the outlet port even after the unit is installed in its angled orientation in the Packards, but that doesn't merit "bench bleeding", IMHO. In-car, one could loosen one of the two nuts on the outlet fitting just enough and have some one push the pedal to burp it, but even that seems like overkill.

I'm gonna be bleeding the wheel cylinders and wanna push all that old fluid out, anyway.

I use a MityVac handheld vacuum pump with their bleeder attachment to catch the spent fluid, but stop and top off the m/c reservoir periodically. I start with the wheel closest to the m/c and work out from there, but make second a pass around the car. Sequence is more critical with tandem systems' especially when diagonally split - even moreso when ABS comes into play.

Rowdy,

Thanks for the link.
I never heard of 'speed bleeders.' They look amazingly simple.
How much do they run?

DanL

I bought a set of them from Oreilly, any local parts store should have them in stock, take an old one to compare sizes. I think I paid $12 a piece for them, but when you're doing it by yourself they're invaluable. One word of caution though, do NOT overtighten them! I did, crushed one of them where the cone that seats into the wheel cylinder has it's little cross-drilled hole in it. Had to buy a new one, but it was a good lesson learned.