PM vs. VAC

[8AV8]

119 mph and plenty of vacuum left to stop the car...and this track is short on the other side of the 1320 mark.

 

[BlackMetal]

Interesting reading here. I have a powermaster setup on my 85 GN. Any signs and symptoms of it going out? Other than the pedal hitting the floor?

Hearing the motor run too long. Red "brake" light flickering on the dash. Coasting through a red light.

Anyways my conclusions at the moment...

PowerMaster seems risky even if you're a saint about maintaining it with new fluid etc. But if you occasionally discharge the accumulator and then see how long the motor runs to pump it back up it'll give you an idea if things are in good working order and may keep you safe. If the motors runs for an excessive amount of time, don't drive it, something is going bad. Still... too many stories about guys just sitting at a red light and suddenly the warning light pops up and the pedal hits the floor.

Vacuum... only way I would feel safe is with an auxiliary vac pump/reservoir but then that's more $, more plumbing, more wiring, more space to mount parts, more hassle over all. No I've never really heard of a vac system failing but lots of guys chasing down problems with check valves seemingly not working properly etc...

Hydroboost is most attractive to me in terms of sheer stopping power and is 2nd best in terms of reliability. The only thing that could really go wrong is leaking power steering fluid but I've never seen a power steering hose or seal completely blow out and lose a huge amount of fluid. Trickle type leaks if anything. Could probably catch it soon enough to be safe. Conversion kit something like $600 maybe more with lines and fittings.... but the more lines and fittings you add to a system the more spots for it to leak.

Manual brakes. Cheap and reliable. Either convert with old S-10 parts or buy a conversion kit with new master cylinder, pushrod, etc. $200-$300 range total. Extra leg effort required while driving. No PowerMaster motor or accumulator to fail, no tapping into the power steering system and worrying about leaks or seals blowing out, no vacuum check valves to mess with. Downside being no power assist. But no fancy parts to worry about failing, the only things in the equation are your leg and the traditional hydraulic brake system. Maintain fluid, bleed brakes, check routinely for leaks, and don't get a cramp in your leg, and you'll be ok.

I'm leaning towards a manual system with S-10 rear cylinders and a Wilwood front disc brake upgrade to compensate for the loss of power assist.

 

[turbofish38]

Vacuum... only way I would feel safe is with an auxiliary vac pump/reservoir but then that's more $, more plumbing, more wiring, more space to mount parts, more hassle over all. No I've never really heard of a vac system failing but lots of guys chasing down problems with check valves seemingly not working properly etc...

Well if the vacuum booster fails you just have manual brakes. Not quite as hard of a pedal as you would with a PM failure.

I'm working on a aux pump set up on mine. GM used a few of them on select models. I'm using the parts off a late 80's vintage Caddy Deville. I've got the parts. All I need to do is mount them and figure out if the low vacuum switch will work when it's under boost.

I've got instant lock up with my system. I need something refined. I've been thinking about trying drifting with the GN. Trying to lock up half the brakes under boost is kind of impossible.

 

[INEEDAGN]

Well if the vacuum booster fails you just have manual brakes. Not quite as hard of a pedal as you would with a PM failure.

I'm working on a aux pump set up on mine. GM used a few of them on select models. I'm using the parts off a late 80's vintage Caddy Deville. I've got the parts. All I need to do is mount them and figure out if the low vacuum switch will work when it's under boost.

I've got instant lock up with my system. I need something refined. I've been thinking about trying drifting with the GN. Trying to lock up half the brakes under boost is kind of impossible.

I was cleaning up an 04 GMC today and noticed that it has something attached between the engine and the booster, it's mounted to the booster and interrupts the vacuum line to it, and has 5 or 6 wires going to it. Is this some sort of aux pump? Kinda looks like it could be. This is just a run of the mill 1/2 ton 4wd, probably a 5.3 liter. Not that I need a pump, but if I found one in the JY I might pick it up.

 

[turbofish38]

I was cleaning up an 04 GMC today and noticed that it has something attached between the engine and the booster, it's mounted to the booster and interrupts the vacuum line to it, and has 5 or 6 wires going to it. Is this some sort of aux pump? Kinda looks like it could be. This is just a run of the mill 1/2 ton 4wd, probably a 5.3 liter. Not that I need a pump, but if I found one in the JY I might pick it up.

Yep. I've seen them too on trucks out in my shop. It would be neat if that one would bolt onto the small dual diaphragm booster. The set up for that one is basically the same as what I'm doing. The only difference is mine is going to be controlled manually more or less. The truck one is controlled by a couple of processors. It's very complicated to duplicate without a computer anyway. There is even a warning light on the dash telling you when it kicks on, or the system is malfunctioning. Hey, there's a market for somebody. Retrofit electonics for the PM.

 

[V6UnderPressure]

Does anyone know if there are other options than the stock PM, vacuum, or hydraboost master cylinders? Are there any performance master cylinders out there???

 

[8AV8]

Master cylinders or boosters? All those components are boosters.

 

[V6UnderPressure]

Master cylinders or boosters? All those components are boosters.

Boosters, sorry. Had a long double shift day at work with the bad weather.

 

[8AV8]

Manual....that is,using no booster. No chance of anything failing or performing poorly with a booster.