Re: Treadle vac disassembly snag
Posted by HH56 On 2019/5/26 13:52:32
With that much corrosion make sure the bore where the seals are positioned is in excellent shape and that the relief passage between the top of the fluid reservoir and the space between the hydraulic and vacuum seals is open. Also make sure the ram shaft is smooth and undamaged the entire length.
The vacuum side seal is thin and fairly simple but if it should leak a tiny bit the vacuum can pull fluid out of the hydraulic section and into the vacuum side if the relief passage is blocked. Conversely, the hydraulic side seal is heavy and robust but is designed to allow a tiny bit of seepage to keep the seal moist and lubricated. If the small amount of fluid that gets past the seal builds up in the space because it can't get to the reservoir it can be forced into the vacuum side by hydraulic pressure as it keeps building up. The bore needs to be in excellent condition on the outer circumference of the seals because if it is pitted vacuum can leak or fluid can be pulled or forced around the outside of the seals.
If the unit was dry and fluid crystallized there is also a possibility the ram shaft has been scored or even pitted around the area the seal was touching. The shafts are not part of the rebuild kits but Kanter has new stainless shafts if yours is the least bit damaged. Also check that the conical spring that pulls the compensator valve closed is intact and functional. It is supposed to be stainless but some have reported finding ordinary springs that had rusted and no longer could pull or hold the valve tightly closed. I don't know if any repro springs are available at retail. A rebuilder that had some made for his personal rebuilds retired and no idea if anyone bought his inventory or if anyone else has made them available.
When reassembling the unit, check the reservoir cover gasket. If it is the typical gasket found in many of todays kits there will be a portion of the gasket that sits directly over the relief port. The port will be blocked if you have the later version BTVs which had the relief port flush with the top of the reservoir and combined with the thick flat cover plate that was usually found on Packards. Apparently the gaskets were designed for use with a different cap than was used on most Packards. Those other caps had a slight raised channel pressed into the cap and centered over the port to provide an opening. To use the port blocking gasket with the flat caps just make a small notch between the hole and inside edge of the gasket so the port can be opened to the reservoir. Some Packards did have a later style cap so if you do have a cap with the channel then use the gasket as is.
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The vacuum side seal is thin and fairly simple but if it should leak a tiny bit the vacuum can pull fluid out of the hydraulic section and into the vacuum side if the relief passage is blocked. Conversely, the hydraulic side seal is heavy and robust but is designed to allow a tiny bit of seepage to keep the seal moist and lubricated. If the small amount of fluid that gets past the seal builds up in the space because it can't get to the reservoir it can be forced into the vacuum side by hydraulic pressure as it keeps building up. The bore needs to be in excellent condition on the outer circumference of the seals because if it is pitted vacuum can leak or fluid can be pulled or forced around the outside of the seals.
If the unit was dry and fluid crystallized there is also a possibility the ram shaft has been scored or even pitted around the area the seal was touching. The shafts are not part of the rebuild kits but Kanter has new stainless shafts if yours is the least bit damaged. Also check that the conical spring that pulls the compensator valve closed is intact and functional. It is supposed to be stainless but some have reported finding ordinary springs that had rusted and no longer could pull or hold the valve tightly closed. I don't know if any repro springs are available at retail. A rebuilder that had some made for his personal rebuilds retired and no idea if anyone bought his inventory or if anyone else has made them available.
When reassembling the unit, check the reservoir cover gasket. If it is the typical gasket found in many of todays kits there will be a portion of the gasket that sits directly over the relief port. The port will be blocked if you have the later version BTVs which had the relief port flush with the top of the reservoir and combined with the thick flat cover plate that was usually found on Packards. Apparently the gaskets were designed for use with a different cap than was used on most Packards. Those other caps had a slight raised channel pressed into the cap and centered over the port to provide an opening. To use the port blocking gasket with the flat caps just make a small notch between the hole and inside edge of the gasket so the port can be opened to the reservoir. Some Packards did have a later style cap so if you do have a cap with the channel then use the gasket as is.
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