Re: Bendix -Treadle Vac - Failure and Fix
Posted by Eric Boyle On 2010/10/4 15:42:48
Craig, STFU.
Here's another good story of a complete BTV failure on a 1958 Mercury and what the guy discovered while rebuilding it:thebigm.info/WorkBrakes.asp
Another Mercury site showing the rebuild method. I especially found this part interesting:
"A little more information on the counter bore...........
The rubber packing fits into the counter bore as shown in the above illustration. The leading edge of the packing seal will go in first followed by the packing expansion bushing and then the washers, retaining ring and finally the leather seal. The counter bore must be free of scratches pitting gouges etc. on order for the rubber packing to do its job. Note that the leading edge seals against the bottom of the counter bore. You exert at least 150 -200 PSI when you step on the brake pedal. That is why the bore needs to be perfect. It really only seals in the first 1/16 of an inch in the bore ...right down in the corner. If you hone the bore you will scratch the surface of the casting disturbing the green anodizing on the casting and allow brake fluid to seep past eventually allowing brake fluid to fill the booster and cause a soft pedal. The green anodizing seals the casting from the corrosion forces of the brake fluid. So if you're loosing fluid and there are no leaks ..... Look again!
When you pull the unit for service it will be full of fluid. Not to mention the vacuum reserve tank will fill up as well. Believe me it holds a lot of fluid. You will be filling all the time....With no visible leaks. This is the number one reason for failure. The casting condition is critical. However; It can be sleeved and re-anodized, but with caution.
Additionally, the inner portion of the packing seal rubs against the plunger (shaft) it too must be free of nicks, scratches etc.
Found here:ford-mel-engine.com/viewtopic.php?f=12&t=149
I also found this picture interesting:
Attach file:
(26.13 KB)
Here's another good story of a complete BTV failure on a 1958 Mercury and what the guy discovered while rebuilding it:thebigm.info/WorkBrakes.asp
Another Mercury site showing the rebuild method. I especially found this part interesting:
"A little more information on the counter bore...........
The rubber packing fits into the counter bore as shown in the above illustration. The leading edge of the packing seal will go in first followed by the packing expansion bushing and then the washers, retaining ring and finally the leather seal. The counter bore must be free of scratches pitting gouges etc. on order for the rubber packing to do its job. Note that the leading edge seals against the bottom of the counter bore. You exert at least 150 -200 PSI when you step on the brake pedal. That is why the bore needs to be perfect. It really only seals in the first 1/16 of an inch in the bore ...right down in the corner. If you hone the bore you will scratch the surface of the casting disturbing the green anodizing on the casting and allow brake fluid to seep past eventually allowing brake fluid to fill the booster and cause a soft pedal. The green anodizing seals the casting from the corrosion forces of the brake fluid. So if you're loosing fluid and there are no leaks ..... Look again!
When you pull the unit for service it will be full of fluid. Not to mention the vacuum reserve tank will fill up as well. Believe me it holds a lot of fluid. You will be filling all the time....With no visible leaks. This is the number one reason for failure. The casting condition is critical. However; It can be sleeved and re-anodized, but with caution.
Additionally, the inner portion of the packing seal rubs against the plunger (shaft) it too must be free of nicks, scratches etc.
Found here:ford-mel-engine.com/viewtopic.php?f=12&t=149
I also found this picture interesting:
Attach file:
(26.13 KB)This Post was from: https://packardinfo.com/xoops/html/modules/newbb/viewtopic.php?post_id=61276