Bendix Treadle Vac Study- Serioius Business!!

Posted by fred kanter On 2010/12/1 5:23:34

I want to bring all readers up to date on what I have accomplished and learned thus far.

I have selected 100 customers who have purchased a BTV rebuild kit and am preparing a questionnaire which will include the reaspon for rebuilding such as: in the course of restoration/ hard pedal/ no pedal upon removing car from long period of non-use/ catastrophic failure in use/ gradual failure in use etc etc.

I have had 10 used units in my stock put aside for internal analysis. So far I have removed the compensating valve/spring/nut assembly and examined them.
Findings:
All 10 leaked when I tried to blow through them by putting my lips to the threaded portion. All were then disassembled Conclusions: 1. When "dry" and not immersed in brake fluid it is not possible to determine if there would leak in service. 2. All have substantial deposits of what looked like "dirt" and are probably rust or from dirty fluid.3) These deposits, from visual examination, would likely cause the valve not to seat 4) Although all were from units out of use and therefore had spent over 10 years with the valves "tipped" only 1 showed signs of a "dented" rubber face. My GUESS is that the system had some petroleum product in it an caused the valve rubber face to soften and deform.

Further analysis to be done:

Finding the presence of "dirt/rust" which might cause abrasion of the primary rubber seal and leaking, I will remove the seals and examine under a microscope.

RESEARCH WITH INDUSTRY EXPERT

I have spoken to one of the largest power brake unit rebuikding companies which has been doing BTV's for many years. In his experience there are two reasons for BTV failures. Comp valve leaking due to incomplete sealing. This is caused by foreign material or deteriorated brake fluid in the system. Fluid loss caused by leaking of the fluid into the vacuum section and being sucked into the intake manifold. Low fluid causing loss of braking. Cause, leaking of the primary seal and the fluid getting by the secondary seal instead of back into the reservoir.

Note: This problem can be caused by the use of an incorrect reservoir cover gasket which blocks the fluid return passage. This has been oted in previous posts in other forums.

OTHER MEASURES IN PROGRESS:

Wear and age are inevitable ( I recently noticed that I'm 65 despite my best efforts not to age) and the eventual wear of components will happen. I will design a simple retrofit BTV cap with a low-fluid sensor and a light to put below the dash. This will give an adequate early warning just like modern systems, similarly can be used manual brakes 35-up.

RESPONSES FROM MY PREVIOUS POSTS:

I requested to hear from members about their catastrophic failures. Heard from one who posted in the forum

Offered a free compensator valve from anyone who felt theirs was defective. NO responses.

Helpful and constructive comments/criticisms welcome. All others can air their differences at your next meeting of the Flat Earth Society

Fred Kanter
Kanter Auto Products
Boonton NJ