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

Hi guys,

About 3 years ago, I had the original BTV unit rebuilt on my beloved '54 Patrician. I filled and bled the brakes at install. Every year I replace the fluid in the master.

Yesterday, during a routine brake line flush, when the valve was opened on the RR brake, I was able to pump the pedal down, and had to manually lift it off the floor. This happened maybe 4 times, when the brake pedal became absolutely stuck in the down position. I removed the entire unit and the plunger is definitely stuck in the down position and cannot be returned to the open/unstuck position. Also, there was fluid and gunk on the bottom of the brake pedal side of the accumulator, looking to have been there for a while, which I know isn't supposed to be there.

Also noteworthy the color of the brake fluid was "OK" when I removed the fluid from the reservoir before refilling to do the line flush. However, at the wheel, it started out a little cloudy/dirty then a gush of dark cola colored fluid came out, maybe 3 pumps before the unit froze.

Thoughts and advice?

No suggestions on the cola colored fluid other than possibly a hose or some contamination or other deterioration is happening.

On the stuck pedal, just for grins check the relief port which connects the space between the seals and the reservoir. See if it's blocked. There was an issue identified with the reservoir cover gasket a couple of years ago. It was also found that at least one rebuilt unit had the port filled with RTV compound.

If the port is blocked, any seepage from the hydraulic seal has no where to go other than be forced into the vacuum side. At the same time, if there is a vacuum seal leak there is nothing to suck except fluid from the hydraulic section. Either way any fluid gets into the vacuum side it can mix with the leather seal lube or congeal all by itself into a sticky goo. It sounds to me like that might have happened.

Early on there was a change in the height of the relief port passage inside the reservoir. The first design had the port stop a slight distance below the top. You can see that version in the illustrations in the service manual. The later BTV versions had the port go all the way flush with the top lip of reservoir.

Packard used a flat cover and with the first version BTV that worked out just fine. With later BTV versions with the raised port, the lid was changed to accommodate it. Most mfgs used a lid which had a raised "bubble" passage or an actual U shaped tube in the lid which allowed the port to function. Packard however, kept the flat lid with the later versions. The newer gaskets for the newer lids combined with the flat lid completely blocks the port outlet area. That prevents the port from ever working.

If you get a rebuild kit, the port solution is to either cut the gasket blocking the port hole or turn the gasket around. Either will provide a bit of space so the port has a slight clearance to lid. That way leaking fluid can return to reservoir or leaking vacuum can suck air instead of fluid. It would be a good idea to pop the lid off any complete units you receive to verify the port is open.

The master cylinder reservoir probably ran dry while bleeding.
Fillr the reservoir and use a screw driver or something to to trip the compensator valve in the bottom of the rservoir. That will let fluid into the pressure side of mc. Theb pump the brake pedal. It will most likely requir 25 to maybe as many as 75 pumps to get the the system replenished with enuf fluid to drive the mc plunger back into position.

Thanks, guys. So, if I do a re rebuild of the BTV and get in there and change out the wheel cylinders and hoses, is there any reason not to switch over to silicone?