Re: Remote brake fill kits

Posted by d c On 2014/8/19 15:57:32

This BTV remote reservoir subject intrigues me. I have read through many threads here with BTV info,concerns, and rebuild instructions along with info from other sources. Taking the "displacement" operation of this system into account, I would like to make a few observations and suggest one addition which may add an extra level of safety. Examining this master cyl arrangement, I agree with those who have already stated there are 2 critical areas in this hydraulic system-the compensating valve seal and the plunger cup seal and these need to maintain 100 percent seal every time the pedal is depressed to provide brake pressure. I hope these parts are being manufactured new, with new materials as delivered in the rebuild kits, and in no circumstances are NOS (new old stock) parts being used in these locations as a tear or failure here will result in instant pedal to floor no brakes with no amount of pumping to facilitate any pedal pressure whatsoever. Decades old rubber in a package,even if never used in service should not be trusted here and may explain some members multiple failures after rebuilds.
While there is no way to "see" the condition of the compensator valve rubber condition while in service there may be a way to keep an eye on the plunger cup seal operation and give early indication of a possible developing issue. As stated on another thread, the air space and the vent passage leading from the rear of the plunger cup seal to the cap sealing surface should be air, not brake fluid and discussion of the cover gasket condition and seal to the cover around that port would be of importance in a high mount resevoir retrofit. Adding this (upgrade) without knowledge of the cover seal condition around this port may leat to brake fluid flowing into the vent passage and behind the seal thus creating fluid infiltration into the vacuum canister and seal failure.
Ideally, removal of the lid and replacement with the cast style and a new lid gasket along with the retrofit cap and tube and remote fill may be prudent. As an addition, wouldn't It be great to drill and install a small brass nipple in the cap right above the vent port and attach a clear 1/16th tube run up the fire wall (ie small engine fuel suppply tube) to ensure air in the vent and create a quick visual upon opening the hood that there is no brake fluid bypassing the plunger rear cup seal. I do not believe the opinion suggested here that a visual of the level in the remote resevoir can be an indication of the cup seal state of health due to the volume of fluid in the container. A tip off of a larger leak in a wheel cylinder maybe, but a small leak in the btv may not be picked up before fluid has already migrated into and done damage to the vacuum canister especially with variations in temperature and level in the resevoir. Any thoughts?
As someone who has not had a "pedal to floor" failure of my btv I am not yet a emphatic "replace or else" member yet as some are here. May I ask, is it the compensator valve seal or the cup seal that is causing the "pedal to floor" more often or is that still not determined. Since the compensator is held "cocked" off its seat all the time the pedal is up, would it be smart to replace this every 5 years since it seems this can be done without removal of the whole unit through the top with cover off or even to chock the pedal just off the stop with the battery removed while in winter storage or will this create problems in the vacuum canister section of the unit. If someone can add a link to the thread with the cover gaskets discussed earlier it may be of help. Dan