Packard Forum Index » V-8 (1955-56)

God, I'm turning into Keith, making multiple posts replying to myself!

Here's a theory: We have the wrong gasket. The return port is sealed up, and the fluid only has one place to go, into the booster. Over time, if no one checks the fluid, the fluid level gets low enough in the reservoir that it doesn't refill the plunger chamber. Therefore, there's air in the plunger chamber causing a compressible area and therefore no brakes. This would explain why you have brakes one minute and no brakes the next.

Now, the question is, how many complete failures have been verified to not have any fluid in the reservoir? It's either this, or fluid leaking past the compensator valve due to either it deforming enough to let fluid past, a chunk of something blocking it open, or fluid leaking past the piston rod and into the booster. There isn't much else that can go wrong.

I think you have summed causes up nicely. I don't recall anyone ever mentioning low fluid--though I don't know how many checked either.

Unfortunately, any one or more of the combination does lead to the failure mode. For those that have the ability to change and don't mind the loss of authenticity, believe alternatives are there. Even fixing the gasket, there is still the issue of valve not closing one time. That one, we still haven't found a true cause for---heat, moisture, angle, all the above, none of the above---it's still a guess..

For those that want to keep some semblance of originality, or can't spare any firewall real estate such as fact AC cars, then the only place is low and that presents a problem. For those that can spare some firewall, the solution is much less painful.

Had a spare moment so I checked fluid level, almost empty, about at top of partition cast into bottom, try to have more whenever I am able to pull it.

Holy smokes! Rowdy & I make a posting and unleashing of information is brought forthwith. This was a very interesting for me tonight after a full day at the office. The experience here in this forum are impressive.

Going back to my failure, I only replaced the compensating valve and got immediate results to the positive. I inspected the compensating valve removed against the new one and could see no visual difference. I did however detect small crimping damage to the larger O-Ring. So all things being equal, should I expect the compensating valve to not work again in 400 miles?

I also wonder if with all the glass beading that goes on into restoring these units if that process could change the ID of the brass fitting that the valve moves inside?

I also have another BTV in the garage. I plan of doing an autopsy with photos this weekend. PM's appreciated on how I can document info for the cause.

Kevin, before you put it back in the car make sure that the gasket around the port is cut away, otherwise I'm pretty confident that you'll suffer fluid loss.

On a side note, if you're dead set on keeping the BTV, make sure you have access to a new front clip and bumper, as I'm sure you're going to need it eventually.

A picture of the 'damaged' O-ring would be nice to see.
U mentioned a "larger" o-ring. The one i have appears to be just one o-ring and i'm not sure it is technically an o-ring. An o-ring is toroidal.

G'day all, I have always been concerned with the fluid level in the BTV fitted to my 48,000 mile RHD 56 Patrician. The filler is almost imposible to access from the top of the car due to the RHD steering column and the heater. I therefore altered a filler top to fit a tube which goes to a clear reservoir on the RH inner guard. I can monitor the fluid level and it actually let me know that one of the original wheel slave cylinders had started to leak, when it started to lose level in the reservoir. I may not have found out otherwise until it was too late. I shall post a picture of the reservoir when I get a chance. As an aside the recently fitted alternator/vacuum pump combo had worked out very well. Best Regards Peter Toet

https://packardinfo.com/xoops/html/modules/newbb/viewtopic.php?topic_id=5721&forum=3

At this point it would be ideal if Allied Signal would be willing to supply us with more exhaustive information about the BTV master cylinder.

Couple of thoughts about this whole BTV thing. Anyone ever have a failure and successfully stopped the car with the emergency brake? I've seen it done, but only successful because of lots of room to do it and a straight road. But it doesn't hurt to practice this maneuver from time to time if you have a questionable brake system.

Another thought about the brakes in general. Weren't there manual brakes available on the '55 and '56 models, and has anyone thought of doing a dual-cylinder manual conversion? It would not require the booster placement. I wouldn't know how these straight hydraulic systems performed in these cars, but some manual drum brake setups are quite effective, when well maintained, and do not require excessive pedal force.

Can't answer the first question, but on the second one you can modify '51-'54 manual setup to fit the '55-'56 cars. It takes a little bit of doing but it's possible. It's also possible to use a HydroBoost hydraulic booster off of a diesel pickup or car which is small enough to fit under the floor. All you'd have to do is plumb it into the power steering lines and you're good to go.