Re: Bendix -Treadle Vac - Failure and Fix
Posted by HH56 On 2010/10/4 8:39:02
Relief port may be a misnomer but I both agree and disagree as to the function.
Agree there may be some "spill off" to lube the back of seal, although from the looks of that gasket and reservoir, minimal to none. However, I think there is much more function to the port than that. If the primary seal were leaking under the pressure of the brake application, that passage would give the fluid a place to travel back to the reservoir or somewhere rather than all being forced into the vacuum side through the vacuum side seal. IIRC, the vacuum side is leather and not much use in stopping fluid pressure of 800-1000psi.
Conversely, if the vacuum side is leaking, while some fluid will be drawn thru if there is a leak, the open vent to atmosphere (unless the remote fill reservoir was in use) will let it draw far more air than fluid unless or until the leak is so bad from the primary the whole seal is submerged. If there is no primary side leak other than the minuscule amount of plunger wipe off, then air would be drawn rather than fluid. If, as been noted, that gasket is essentially closing the port, that might explain why so much fluid is being drawn in on the units Keith has seen.
I'd be curious as to any opening in the cover with that arrangement--or if there is an optical delusion in the photo as to height of the port at some point. With that gasket, doubt it but if you look at the illustration, you see the port is open to the fluid chamber and appears lower. Is there any kind of relief channel? This gasket from a NOS Packard kit 436318 for 52-4 version doesn't even have the hole which means the port would be as the illustration-lower than mounting flange.
There is a different kit for 55-6 so wonder what other changes besides vacuum side valves and response were made in the versions Packard used .
Attach file:
(24.81 KB)
Agree there may be some "spill off" to lube the back of seal, although from the looks of that gasket and reservoir, minimal to none. However, I think there is much more function to the port than that. If the primary seal were leaking under the pressure of the brake application, that passage would give the fluid a place to travel back to the reservoir or somewhere rather than all being forced into the vacuum side through the vacuum side seal. IIRC, the vacuum side is leather and not much use in stopping fluid pressure of 800-1000psi.
Conversely, if the vacuum side is leaking, while some fluid will be drawn thru if there is a leak, the open vent to atmosphere (unless the remote fill reservoir was in use) will let it draw far more air than fluid unless or until the leak is so bad from the primary the whole seal is submerged. If there is no primary side leak other than the minuscule amount of plunger wipe off, then air would be drawn rather than fluid. If, as been noted, that gasket is essentially closing the port, that might explain why so much fluid is being drawn in on the units Keith has seen.
I'd be curious as to any opening in the cover with that arrangement--or if there is an optical delusion in the photo as to height of the port at some point. With that gasket, doubt it but if you look at the illustration, you see the port is open to the fluid chamber and appears lower. Is there any kind of relief channel? This gasket from a NOS Packard kit 436318 for 52-4 version doesn't even have the hole which means the port would be as the illustration-lower than mounting flange.
There is a different kit for 55-6 so wonder what other changes besides vacuum side valves and response were made in the versions Packard used .
Attach file:
(24.81 KB)
This Post was from: https://packardinfo.com/xoops/html/modules/newbb/viewtopic.php?post_id=61201