Re: Bendix Treadle Vac Study- Serioius Business!!
Posted by fred kanter On 2011/2/4 21:41:16
BTV FAILURE DIAGNOSIS
A v-8 owner had a BTV rebuilt and it suffered sudden failure soon after. It was returned to the rebuilder who checked it, perhaps re-rebuilt it and returned it to the v8 owner. It suffered the same failure soon after.
This chain of events has occurred numerous times that have been reported on Packardinfo.com and the BTV is blamed for having an unsafe design. There are a significant number of members who advocate replacement of the BTV with a modern unit.
I made an arrangement with the V8 owner to purchase the unit for research. Here is what I found.
Photos to be attached when I figure out how (help appreciated)
See photo 2: Some type of silicone sealer has been used at the top of the lower counterbore. See curved sealer after washer was removed. Note, there is no seal needed at this point, none was used originally and its presence in the hydraulic system could lead to seal/valve failure.
See photo 1: Fluid return port plugged with silicone sealer.
This explains the failure, fluid cannot be returned to reservoir , when cavity between hydraulic rubber seal and \metal/leather seal fills up, it will be sucked into the vacuum section.. Eventually all the fluid is depleted and the brakes do not function.
It is clear to me that the rebuilder (not identified by V8 owner) is incompetent and does not understand how the unit works.
BAck in the 50's/'60's there were millions of BTV's on the road, rebuilders did hundreds of thousands of rebuilds and did them well. That would explain why there were few problems then and the above example explains why there are frightening problems now. Keep in mind that if a modern master cylinder is rebuilt by an incompetent rebuilder it may fail also.
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A v-8 owner had a BTV rebuilt and it suffered sudden failure soon after. It was returned to the rebuilder who checked it, perhaps re-rebuilt it and returned it to the v8 owner. It suffered the same failure soon after.
This chain of events has occurred numerous times that have been reported on Packardinfo.com and the BTV is blamed for having an unsafe design. There are a significant number of members who advocate replacement of the BTV with a modern unit.
I made an arrangement with the V8 owner to purchase the unit for research. Here is what I found.
Photos to be attached when I figure out how (help appreciated)
See photo 2: Some type of silicone sealer has been used at the top of the lower counterbore. See curved sealer after washer was removed. Note, there is no seal needed at this point, none was used originally and its presence in the hydraulic system could lead to seal/valve failure.
See photo 1: Fluid return port plugged with silicone sealer.
This explains the failure, fluid cannot be returned to reservoir , when cavity between hydraulic rubber seal and \metal/leather seal fills up, it will be sucked into the vacuum section.. Eventually all the fluid is depleted and the brakes do not function.
It is clear to me that the rebuilder (not identified by V8 owner) is incompetent and does not understand how the unit works.
BAck in the 50's/'60's there were millions of BTV's on the road, rebuilders did hundreds of thousands of rebuilds and did them well. That would explain why there were few problems then and the above example explains why there are frightening problems now. Keep in mind that if a modern master cylinder is rebuilt by an incompetent rebuilder it may fail also.
Attach file:
(186.14 KB)
(93.59 KB)
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