Re: BRAKES: Easamatic Power Brakes aka Bendix Treadle-Vac--Change or Not??

Posted by Chuckltd On 2009/5/18 1:34:37

This appears to be a bone of contention here, but I'll give my take on it anyway. In the last 15 years I've had about 30 some different cars with quite a few different systems and setups. Single res. drum/drum manual and power
Dual res. drum/drum manual and power
Dual res. disc/drum power (never had manual yet)
Dual res. disc/disc power
Dual cylinder disc/drum power
and yes, there's a difference between dual system and dual reservior. So far, the only total hydraulic failures I've had were on the dual system/single res. type and on disc/drum dual res.with power assist. On a lot of dual system cars with power brakes, people tend to not notice when the rear brakes have failed or started to. I recently sold a 78 LTD that has no rear brakes but most people wouldn't notice. In fact, lots of vehicles I've worked on appeared to have not had functioning rear brakes for years. If you have a front system failure and your rear system is not up to par, then you're in for trouble. Another 2 cases were an 85 Olds and a 87 Merc. When these blew a line, the other half of the system worked but only once as both systems draw fluid from the same reservior and when it's been emptied neither will work.
Cases like those are where the false sense of security is apparent. If you maintain both sides of the system as you would a single system car, then you're ok. That includes the proportioning valve and warning light system. All too often, these are stuck or filled with crap and the warning light never comes on to let you know that something's wrong. Maybe I've been lucky. How many times has anyone let a leaking rear wheel cylinder go until they have time on a dual system car? How many vehicles have never had their brake fluid changed or flushed till something failed? I'll take a properly maintained single system any day over a neglected dual.
Bottom line: Dual system is no safer than a single unless properly maintained, in fact it may be worse.