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Tom,

This BTV was gunky, too. The lines were successfully flushed and new wheel cylinders installed, and the bottom of the reservoir cleaned up, but a complete teardown is now almost certainly in order.

One reason I say "almost," (I'm a born optimist when it comes to fixing cars, and sometimes this outlook has saved me a lot of time and trouble) I also plan to have the brakes re-adjusted, the system flushed again, and bled 'til it won't bleed no more. Idea being, this could possibly free something up, or the remote possibility that the fluid is disappearing as air bubbles are worked out of the systmem, assuming it wasn't bled thoroughly to begin with (but I'm pretty sure it was).

I have used DOT 3 fluid, feeling this was the no-brainer fits-all alternative, but never thought to ask the specific question about possible better results with other fluid that might help the seals seat better.

Also, and this is strictly a "snake oil" solution, wondering if there might be an additive that could soften up some of the seals or help them seat properly. I'm sure they're dried out at the least, since they didn't even get bathed in proper brake fluid for who knows how long.

Again, these are short-term "experiments" and doubtful if they will work at all. I know what it needs: Tear down and eliminate all mysteries. But I'd rather get it as good as possible first, so the mysteries aren't overlooked, or worse, the re-build creates more of them.

I hate to put more brake fluid in the car and then start it if the fluid is geting sucked into the "vacuum side" and thence into the intake manifold and the engine. I am planning to disconnect the vacuum hose at the manifold and plug both sides so I can start the car.

Is there any danger to the engine if there is still some brake fluid in the oil? Has running the car with brake fluid coming into the engine potentially glazed the piston walls or done any other damage? Right now, the car starts and runs like a champ, but I don't want any problems cropping up down the road.

Anyone see any reason not to blast the reservoir with some brake cleaner? It's my go-to product for ungunking just about anything without damaging it.

DOT 3 is fine. That's what was there originally. I doubt you will find air in the lines. If there were, you would have a very soft spongy to poor brake pedal. But it certainly won't hurt to do it again.

I'm not aware of any additive that will help much on the seals. The sealing surface is small and once dried, subject to any abrasion that might be present. Old dried fluid and whatever gunk is with it can make a fine scouring powder. There is also the pot metal casting and the chrome piston surface. I have taken several units apart where the casting has so many pit cavities the outer seal ring surface could barely find a solid surface to rest against -- let alone seal against. Same with the piston. Where the lip sits, more than one have had a rough ring etched into the metal finish.

I'm thinking the brake cleaner would not do any good with the problem. You could risk not being able to get all the stuff out to try doing anything with the system intact.

Doubt you will have had any engine issues with burning fluid. More importantly if it is sucking that much to be concerned about engine damage, I'd be more worried it would worsen and you would suck enough fluid out between a successful stop to have an empty master and not be so lucky on the next. I personally would not drive the car with the situation.

Would it not be easiest and safest just to rebuild the BTV, thus correct the most probable failure?
I did the rebuild using Kanters set and piston, and of coursehttps://packardinfo.com/xoops/html/modules/article/view.article.php?c8/404
It was not too difficult.
My 2 ?rer (Norwegian cents).

Tom

Rocky46 Quote:

In a "hotly controversial" word: NO. There are many threads on whether to keep & rebuild the now infamous BTV OR replace it with a new, modern dual MC setup. As have many others, I chose the latter:

http://www.1956packardpanther.com/Panther/powerbrakes.html

My motivation was that I actually drive my 55 Pat a lot and over the years, I personally experienced FOUR (4) failures of different, professionally rebuilt BTVs before I gave up and engineered a workable modern replacement.

When you step on the Easamatic brake pedal in heavy, closing traffic and suddenly NOTHING HAPPENS, that will put the fear of god into you. I've had my conversion on my Pat for TEN (10) years and it still works perfectly, every time.

JMHO,

Craig

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In the first case, the brake cleaner is so volatile that it dries off of parts and leaves no residue, so I think it would evaportate out of any fluid it mixes with as well. I'm fairly confident it wouldn't hurt anything, but just about positive that it won't help. I just like to try unlikely stuff that has an outside chance of working, because sometimes it actually does.

Failure of "rebuilt" BTV units does not surprise me, if these are purchased in exchange for a "core." The rebuilds are going to be done at a speed and with the care that suits economic interests of scale. I really lean toward having the unit rebuilt by an individual who does MCs one at a time and has experience with this type of braking system. There is at least one such person in the area. Also, I would trust my current mechanic to follow the excellent firsthand instructions provided by Ross, along with the Shop Manual's original procedure, to do a job on the original brake setup that I can have some faith in, with of course precautions in how I drive and my skill at getting to the finely tuned parking brake! I have a fair amount of practice with that already.

Evidently, these BTV power brakes were not blowing out on a regular basis when most of the cars were newer and out on the road in great numbers. Not just Packards, but other makes that used the BTV, would have caused unending mishaps if their percentage of failure was as high as the older and rebuilt units is. This leads me to believe that these things just didn't have a very long useful life, and were difficult to rebuild to a reliable standard, especially after they became rare and unfamiliar to most mechanics and rebuilders.

I kiind of suspect the pot metal construction is just plain not sturdy enough to hold things together to spec as it ages.

What's happening now:

I have disconnected the vacuum hose at the manifold, plugged both ends securely, and hence have a very firm pedal. Residual fluid did drain out of the end of the vacuum hose. I had to be very careful removing it and plugging it, as it is quite brittle. So far, so good.

So, no more brake fluid in the intake, but no power brakes, either. I plan to experiment with how the "manual" setup works out if the vacuum hose is plugged, and with it open to atmospheric pressure. Just another dumb experiment.

The fluid reservoir is empty, so I guess now would be the time to blast some brake cleaner in there and let it sit with the plug out overnight to evaporate. Then I'll top off the fluid and see how hard I have to stand on the pedal to get any stopping power.

No worries, though:
I'm an excellent driver. I drive slow in the driveway.

On a related vacuum note: Is there any reason to remove or service the vacuum connection and valve assembly on the intake manifold? The service manual only mentions this in the "trouble-shooting" section regarding pedal "flutter" on light application of brakes. It attributes it to a dirty screen. But might other gremlins live here in this thing? I'm ruling out nothing at this point.

There were two or three type valves used. Here is one that has a hard rubber plunger that seals via a machined seat in the valve. Another type had a flat stamped piece of brass which seated against a machined surface. This type can have the plunger deteriorate and the other have the flat plate corrode. Either type can have some of the steel parts rust and flake off or get gummed up so the respective plunger types can stick or not seat well.

If your vacuum system is not intact and connected to the brake, there is not an easy way to tell if the valve is not sealing. Usually once the engine stops you can push on the pedal after a few minutes and sufficient vacuum will be held in the reserve canister for an application or two. If there is no reserve vacuum at all or it bleeds off quickly then assuming no bad hose or canister, the valve is the usual suspect.

Without an intact system you can put your finger over the tube to brake booster and stop the engine to see if vacuum leaks off or remove the valve and check it out or provide your own vacuum source to the hose going to valve and see if any air is drawn thru the valve when engine is stopped.

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Thanks, HH

That looks just like mine. Just couldn't find it in the Shop Manual. Maybe it's somewhere in the "Engine" section, but they did a pretty poor job showing the routing of the vacuum lines, so I wasn't surprised that the valve wasn't shown either.

This will be back-burnered until I figure out what might happen with the MC. I'm afraid any more variables thrown in now will probably confuses the cook.

For now, it's sittin' one more day before the great experiement of filling it up with fluid and seeing how it stops with manualized power brakes--all in tip-top shape, though.

From what I've seen so far, pulling the MC, cleaning it, and putting in the necessary parts to make it work right can be a local job. Then, I'll know who to blame and won't be sendng it back to a faceless rebuilder who will swap me for yet another brightly painted unit of unknown origin.

If this runs me over 300 bucks, I might not have it on the road again much until after next winter. The cold weather is a-comin' in. Ideally, I'd like to take it on a trip down south and park it in a nice warm, dry shady spot.

Got out to top off the MC reservoir. It really did't take much. With no vacuum to the brakes, it takes a lot of pedal pressure to stop, but the pedal is solid and does not drop to the floor. Once the brakes take hold it stops well. It takes a little for the pedal to return after a stop, but I imagine that's not unusual with no vacuum available.

I gave it quite a bit of exercise, with a lot of stops and starts. I hope that maybe somethiing in there loosens up a bit. Unfortunately, I know of no way to test it out with the vacuum re-connected that doesn't involve the possibility of sucking more brake fluid through the intake.

Even though it's getting late in the season, I hope to get this thing settled before I store the car, and get some more miles on it.

I'm planning to park it for the winter in my back yard, on top of some asphalt rolled roofing to keep out the ground moisture. My main concern is to protect the windshield and front end from anything the snow blower throws up. I think one of those blue tarps will probably work. I want to avoid trapping moisture under the car or anwhere inside, so am planning to avoid the whole car cover thing.

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Pedal should come right up vacuum or no. I suspect the fluid inside has gummed up & the leather piston seal is sticking to the sides of canister.