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HMM? I had the BTV rebuilt considerably longer than eight years ago. Based upon what I have read and heard I drive my 400 a good deal further than most Packard owners. I have had to adjust the brakes a few times. I do run silicon fluid and if heat from the exhaust manifold is a problem, perhaps the silicon brake fluid has diminished that. I am interested in the results Fred comes up with by contacting a wide cross-section of 52-56 Packard owners. I believe there are many who access this site and just read.

Randy,

We sell BTV kits to owners of about 8 makes of cars, I will survey all makes for thir experiences and try to get any recently failed units sent to me to analyze in our shop

We also have a 1950's vintage original Bendix Power Brake testing machine especailly suited to Treadle Vacs

Thanks for your support and cool head.

Fred

I don't know about the cool head and I was just stating my own personal experience. I do look forward to your survey of BTV owners. If you would can you break them down as to toeboard mount or above the steering column mount? Just trying to understand why one would fail more than others, if it does???

Good suggestion, thx

Another thing that might be interesting is who actually does the rebuilds. Some specialize in them and hopefully change what is needed, others might call a rebuild professional if all it gets is a new seal, gaskets or coat of paint.

I have also seen some pretty crappy looking pistons after a long sit that should have been replaced. Until recently the availability of repro pistons was not well advertised or known. On a quick check, I don't even see them listed on Max's site so maybe some that should be gone are not.

Same with castings or the underside of steel valve body. If the piston seal bore area is pitted, it can leak but how many know that and put in a new seal assuming all will be well or a new valve with fresh rubber assuming it will conform and seal on a rough surface.

One thing I have seen on some systems are small chunks of congealed something in the fluid. What they are other than aged or contaminated fluid or how they're formed I don't know. If they are present, there is nothing to keep them from being drawn into the cylinder. I wonder if one of those chunks might get caught on the compensator valve lip and prevent a solid seal.

All this BS about "Mercedes used it so it must be ok" is about to be refuted:

Quote:

Source:gullwinggroup.org/history.php

Paragraph #18 if you don't want to read it all. Apparently Mercedes experienced BTV failures back in the '50s when we were told by "those who were there" that there were none.

Post #5 here:forums.190slgroup.com/showthread.php?5799-T-50-Brake-Booster

Sticking your head in the sand and complaining about the "sky is falling" crowd still doesn't change the fact that this unit is failure prone across all makes and models, and was superseded by safer units.

Amen Eric, amen!

Craig

providing the startling experience of no brakes at all if the booster unit failed.
That may be the easy way to write it, because the author probably didn't know exactly what, if anything, that failed.
The failure of the booster (vacuum) unit will not cause a no-brake condition. I have stopped the car on a hill without the engine running and no booster in evidence because the vacuum was used up. The TV is still able to apply hydraulic pressure albeit requiring a much greater force to the pedal. The statement as written is not true, but we don't know what actually failed in this anecdote. It may well have been the hydraulic half of the BTV. In any case the example is in error.

Apparently that author is not the only one who would disagree with you: Original Mercedes SL

If you understood how Mercedes used the Treadle Vac in their cars you'd realize that the statement is correct.

Funny how Mercedes only used the BTV on the first 353 300SL's, they realized rather quickly that it was unsafe, and even upgraded existing cars with the newer unit.

to HH56

We refer to the deposits in the BTV reservoir as "crud". We believe it is a result of brake fluid that has absorbed water (it's hygroscopic). Car manufacturers all recommended that the brake fluid be flushed and replaced regularly which would keep this from occurring.

I guess it's possible the a piece of crud could lodge under the comp valve adn cause it to leak, but that doesn;'t explain the failures we have been hearing about that happen 1 yr after rebuild.

To Eric;

Interesting inofrmation on the 300SL etc.

I do not recall ever saying there no failures "back when".
Perhaps my memory is not serving me well, so please point out just where it was written.

I do know that today I recounted the story of my father's Lincoln suffering BTV failure with me riding in it in 1957.

As you say you havealways answered my questions, I would most appreciate if you would answer this one.
Thanks