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Hi all, Two posts in the one day, I must be hooked! Please be cautious in changing to silicone brake fluid (SBF)in the Esamatic brake system. I USED to convert all of my hydraulic brake cars to SBF, almost entirely because it was lubricatng to the seals and did not attract/absorb water. (currently have 4 packards on SBF)
I recently had an experience whereby about 6 months after I converted my 56 Patrician to SBF, the brakes started to not release, to the extent that on at least 3 occasions they locked the brakes up completely. My diagnosis was swelling of the main seal covering the compensator port, not allowing fluid to release back to the master cylinder reservoir. It would appear that the nominal 7% seal swell due to the SBF was sufficient to block the system, (and it is one of the most probables in the factory diagnosis). I quickly pumped and relaced the SBF with one of the low hygroscopic DOT 4 fluids and have not had any problems since. I have installed a monitoring light under the dash which indicates when there is pressure in the brake system and so long as it goes off quickly I am happy that the 7% seal swell may not be permanent and shall hopefully have no further system lock-ups. Happy Packarding Peter Toet

Peter -

I have two V8 Patricians with DOT5 silicone brake fluid running in their veins. The conversion on the first car was done by the previous owner, but I suspect it was merely a drain/flush and refill. I did the conversion on the other car, but replaced every piece of rubber in the system - including the compensator port valve stem.

Though the first Patrician has been in dry-dock for several years, I did drive it quite a bit, including a couple hundred interstate miles, but it began to exhibit some grabbing in front brakes just moving it in and out ofthe garage. The other Patrician did not see much road use as it went on the back burner when I acquired my Carib, but I can back the car in and out of the garage with no grabbing - unlike the other Pat.

The only ill-effect I noticed from the use of DOT5 was premature failure of the hydraulic brake light switch, though not consistently. It makes me wonder if a new run of switches produced with a more modern rubber might alleviate that, but I ain't holding my breath on that ever happening.

As such, I have to ask if you replaced all the rubber components - including that compensator port valve - when you converted to DOT5.

The only parts which I replaced were in the booster, I flushed out the rest of the system with compressed air, Methelated spirits and compressed air again. I have used this method on quite a few cars (and bikes) without problems, until the Patrician and a late Eighties Nissan. Some vehicles appear to cope with the nominal seal swell (approx 7%)of the SBF, while others cannot.

What kind of bikes do have????? Any Green Eggs, 4ours, Crockers or hack outfits????? Circus bikes or anything else obscure in the way of bikes???
I have a 48 Chief and a 56 Cushman Eagle 8hp. Both are just nice riders. One 47 Chief parts bike.

i measured a compensator port seal. It is only just an O-ring type arrangement bonded to the trip needle of the compensator assembly. 7% would only be about 1/32 of an inch max. In my opinion that is not enuf to cause any problem.
The compensator port and its operation is very CRUDE at best. It is not really a valve but rather just a a kind of dump gate. The plunger has a washer affixed to the pedal end that only trips the pin that cocks the valve open and it does it by alot of angle.

My treadle vac on my 56 was converted to Silicone 3 or 4 years before i got the car and it ran just fine for about 4 years and 10K miles there after with no problems.


BTW, u refer to it as an ease-a-matic. My understanding is that the 56's All had Treadle-Vacs?????

Clarification: The compensator port seal is a very sloppy fit in the port housing. If u remove the spring that holds the assembly together then the seal and pin that it is affixed to can be shifted around A LOT. The seal only lays flat against a flat surface to create the seal. So it is NOT a seal in the sense that a wheel cylinder cup is a seal or a transmission or axle seal is a seal. Not at all.

Hi Packard V8, I just spent 30 minutes drafting a great reply to you about your last three replies then lost the lot when I ran out of your threads, then lost it all. Oh the joy of computers!
Bikes? I am not sure about what green eggs are but I guess that they are Army bikes. I have a 1917 Excelsior Model (1000cc) ex US army, a 1927 Harley J ex army (1000cc), a 1939 Harley WLJ 1200cc, ex Japanese army (repatriated from Sumatra in 1985), a 1941 Indian 741B outfit ex Australian Army . The closest thing to your 48 Chief is my 1928 matchless X3 (1000cc) in which I am running 44 Chief rods, rollers and a hand made crank pin.
You are so right in that the compensator valve appears to be a very crude tipping device and I was very surprised that I achieved the lock-up problem. The trouble-shooting suggested seal swell so i changed the fluid and it has worked since. I am a great believer in "if it aint broke - don't fix it" I did replace the compensator valve with a NOS part when I put the reconditioned vacuum unit in.
You are most probably correct that it it is a Treadle Vac unit and I am not fully up to scratch on the fitments of a 56 You are also correct in that the compensator seal simply sits against a face, but once you have pressure in the master cylinder doesn't the pressure force a pressure seal on the Compensator valve until the master cylinder piston tips the compensator valve rod, to release the pressure? What do you think? Best regards Peter Toet

Hi Packard V8, I suddenly remembered that the seal swell problem related to the main piston seal and the seal swell meant that it did not come back as far, which affected it's ability to tip the compensator valve seal. it did not relate to seal swell on the compensator seal at all. best regards Peter Toet

Peter -

When converting to DOT5, I've used alcohol (as well as aerosol brake cleaner) to flush out steel lines (that were otherwise in good condition), but never attempted to clean the rubber parts with alcohol.

My understanding is that DOT3 (or DOT4) will become impregnated in the rubber parts and those that are exposed to air will continue to draw water (due to the hygroscopic nature of glycol-based fluids) - even with the system otherwise full of silicone-based DOT5 (wich is essentially inert). As such, I simply replaced all the decades-old rubber parts.

However, in a much newer car, I did notice an incredible amount of swelling of the rubber diaphragm in the master cylnder cover of conventional dual-chambered master cylinder when I flushed it with aerosol brake cleaner from a DOT3 system. After removing it, the diaphragm returned to its normal hape after giving it sufficient time to ai dry. (Good thing I didn't introduce any of that cleaner into the reservoir.)

I'm no engineer, but my gut feeling is that you have experienced some sort of reaction between the DOT5 and whatever chemicals might have remained in the old rubber parts.

Keith -

"TreadleVac" was the moniker given by Bendix. I don't know whether it was a matter of trademark rights or marketing spin, but Packard used the term "Easamatic" to describe the power brake system - even engraved in the rubber brake pedal pad through the 55th Series.

Packard also used the term "Mag-Nu-Matic" to decribe the Trico windshield washer system they used on these cars - vacuum-powered, but activated by small solenoid.