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That is a something that Fred and I have noticed that we tend to see the crystallization primarily on MC that are aluminum. We get numerous amounts of cores from the various makes and models that we sell for and do not notice the crystallizing on the cast iron MC. So flushing the system regularly is very important.

The unit has been cleaned and reassembly of the hydraulic side has been completed. But during cleaning we found the retainer plate for the return spring was broken so that has been replaced.


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I disassembled the power piston today. It has been one the dirtiest that I've seen in a while. It actually has a brake fluid line from where the fluid had been sitting in the vacuum can. All the parts will be cleaned and inspected. Reassembly will start in the morning.

Thanks
James

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Then offer to diagnose and rebuild BTV's for free has ended. We have received enough units to make a report when they are finished

So it is really the master cylinders that fail and not the power assist unit of the assembly then.

John

That was never in doubt

The vacuum section has been reassembled and the unit will be tested in the morning both on the hydraulic side and vaccum.

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Fred-
given this information, how often do you recommend flushing the system and do you suggest silicone fluid?

Yes I recommend silicone (DOT 5), we use it here. As long as you COMPLETELY remove all glycol based fluid, (DOT 3.4.5.1) there is no neeed to change it as it does not absorb water.

If using DOT 3.4.5.1 then I recommend flushing every 2-3 years. NO scientific proof, just a measure of caution

Fred
Thanks for the time, effort, and expense expended on behalf of all Packard owners with cars that have the BTV brake system...(James too). I would change to silicone B/F but am unsure what kind of solvent I would use to flush Dot 3 fluid out? Also with a current BTV system in my 1953, 2662 there has been no signs/symptoms of failure....but.... If brake fluid is in the vacuum chamber and it is not changed what then? I know my BTV has worked for the last 14 years, and the fluid changed when hoses, wheel cyls, lines and brakes were changed/repaired at least 2 times. What do you suggest?
Thanks
Steve

Denatured alcohol. Lacquer thinner. Are 2 i can think of. Just need to blow air thru lines.