Re: Treadle Vac Master Cylinder Cap

Posted by HH56 On 2022/1/14 14:14:20

Yes. The reservoirs are vented open to air on the regular BTV. If the car has had a remote fill added and a regular or an aftermarket replacement cap was drilled and threaded for a hose fitting then the vent hole must be plugged.

One of the forum posters recently found a cap that fits which might be worth looking into. It has a built in bladder to allow the fluid expansion etc . I think he posted the info on the forum late last year. One of the issues with the old open air venting system is since non silicone based fluids collect moisture the fluid deteriorates and needs to be changed on a regular basis.

Most of our old Packards rarely see the fluid changes so the fluid becomes gummy or even has hard crystals develop and float around. Those hard crystals do not play well with the BTV compensating valve and I suspect could be part of the issue where suddenly there are no brakes at one stop but everything is OK on the next. If a crystal landed on the valve seat preventing a tight seal the fluid is forced back into the reservior instead of out to the wheels.