Re: CAUTION ON THE USE OF SILICONE BKAKE FLUID IN ESAMATIC BRAKE SYSTEMS

Posted by BH On 2007/10/23 18:35:09

Peter -

I've not personally experienced a broken compensator port valve spring in operation, but found one in a unit that someone sent me to inspect and supply them with good used parts (for those not supplied in the minor kit). Also, the spring from the T-V unit in a 1956 Patrician that had been left in a garage since 1967 (until I purchased it in 1990) was corroded and ready to break.

As far as actual use and reliability of the Easamatic/TreadleVac system, my father purchased a brand new Exec hardtop in 1956 and put 74,908 miles on that car through 1963, when he replaced it with a '63 BelAir. Imagine all those miles (including two 900-mile round trips to Chicago) with a single-chambered master cylinder, no HEI, no ABS, no airbags or seat belts. (GASP!) It's amazing that any of us ever lived to tell the tale - LOL!

In the examples that I've personally seen, the corrosion that occured and lead (or would lead) to failure of this fine-wire spring is something that took place over many years. The problem is that glycol-based fluids like DOT3 and DOT4 are hygroscopic; they will draw moisture right out of the air - even through rubber. Over time, moisture in the system will take its toll on the internal metal parts - from master cylinder to wheel cylinders. In fact, wheel cylinders with aluminum pistons set in a cast iron bore are particularly prone to bimetallic corrosion and can sieze. Pitted wheel cylinder bores and master cylinder plunger will work like a cheesegrater on the rubber seals.

Regardless of what master cylnder is used, it is important to go through the brake system, "from stem to stern", in these old vehicles and throughly inspect all components. Even when the cylinders are in good shape, I prefer to replace all the rubber parts in the hydraulic system, and upgrading to DOT5 follows naturally. (However, DOT5 appears to be a "no-no" in ABS systems.)

Last but no least, I've not found much problem in the vacuum section of the TreadleVac. With a bit of care and patience, the rubber gaskets can be freed from the metal components for inspection. However, unless there has been an obvious problem with power assist that is not external to the T-V unit, disassembly of the vacuum piston assembly is usually not necessary.