Bendix Treadle Vac Diagnosis
Posted by fredkanter On 2016/8/10 13:52:36
A forum member sent in his Treadle Vac which was failing. We've offered to investigate and rebuild a unit to document what the problems were.
First step is to remove the reservoir cover to see the conditions there, see photos.
Photo 1 There is an extensive amount of crud caused by long term storage and not flushing the brake fluid once in a while
Photo 2 And I mean EXTENSIVE!!
Photo 3 As indicated by the white pointer, the bypass return port is blocked with crud and had to be unplugged using a drill bit by hand This port routes fluid that leaks by the primary seal back into the reservoir. If the bypass return circuit is blocked the fluid is then sucked into the vacuum section and the reservoir level goes down. If it goes down too far the brakes will fail.
Instead of cursing the Treadle Vac unit, all ire should be directed to the previous owner who did not maintain the system by flushing and refilling it......... or to the current owner.
It is not the Treadle Vac unit that is at fault, as a manual system will eventually fail also if not properly maintained. The best comparison I can think of is a water pump. If a system with antifreeze is not flushed and refilled periodically the water pump lubricant in the fluid gets depleted, then rust/scale form and get embedded in the seal. Then a leak happens. Nobody curses the water pump as everyone knows that they eventually fail, especially sooner if proper procedures are not followed.
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First step is to remove the reservoir cover to see the conditions there, see photos.
Photo 1 There is an extensive amount of crud caused by long term storage and not flushing the brake fluid once in a while
Photo 2 And I mean EXTENSIVE!!
Photo 3 As indicated by the white pointer, the bypass return port is blocked with crud and had to be unplugged using a drill bit by hand This port routes fluid that leaks by the primary seal back into the reservoir. If the bypass return circuit is blocked the fluid is then sucked into the vacuum section and the reservoir level goes down. If it goes down too far the brakes will fail.
Instead of cursing the Treadle Vac unit, all ire should be directed to the previous owner who did not maintain the system by flushing and refilling it......... or to the current owner.
It is not the Treadle Vac unit that is at fault, as a manual system will eventually fail also if not properly maintained. The best comparison I can think of is a water pump. If a system with antifreeze is not flushed and refilled periodically the water pump lubricant in the fluid gets depleted, then rust/scale form and get embedded in the seal. Then a leak happens. Nobody curses the water pump as everyone knows that they eventually fail, especially sooner if proper procedures are not followed.
Attach file:
(323.51 KB)
(227.24 KB)
(306.69 KB)
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