PM vs. VAC

[chopped39]

This is a sore subject with me I do not trust anything that has control over my brakes.power master is an unpredictable pos .Wrecked my car because of it.I will admit i never had a problem with it. But when i did there was no warning. The hydraboost is nice but if something breaks tensioner,serp belt or the shaft in the power steering pump you are not stopping or steering . I had a power steering pump fail in a rather large bread truck.soiled my shorts on that one.Everyone is gonna have a differant point of view on this subject.I went vacuum .Its not to much money it bolts right in.Just my 2 cents

 

[Black Power]

I will never use a powermaster again.

 

[little]

I don't know what to do- car has 80k and I don't want the pm to fail on me. I don't drive my car a lot but when I do I need good brakes!

 

[thepremier]

When I bought my 87 GN roughly over a year ago, it was running the Powermaster brake setup. Everything was perfectly fine up to about a month ago when the Powermaster was starting to go bad on me. I kept hearing the continuous clicking, I believe it was the accumulator that needed to be replaced. Anyhow, after doing research on the powermaster and vacuum setups, I decided to go ahead and convert to the vacuum brake system. I received my vacuum brake kit a couple of days ago in the mail, and swaped it out myself. At first I was skeptical about the whole procedure, but after installing the vaccum setup, I am definitely happy that I decided to go through with the conversion.

 

[54Rich]

Has anyone tried a simple manual brake MC? No fuses, no vac, no worries

My wife will be driving this car, brakes Must work, always.

Rich

 

[RobS]

I am intrested in a manual brake set-up as well. Sometime around 1978-1981 manual brake were avaliable on the Chevrolet g-bodys. The master cylinder can be purchased at local parts stores no problem. I can't find a manual brake car in the junkyard to get the pedal and push rod. I think the push rod is unique the the manual set-up. I am not sure about the pedal.

 

[zeus87gn]

Brian has it right. The PowerMaster must be proberly maintained to function correctly.

- Change/flush your fluid every year or two. Use synthetic DOT4. It takes higher temperatures and works better in the high pressure system IMO.
- Cycle the accumulator every couple of months, or when ever you check you fluids, to remove any possible air that may get introduced. It makes a difference to the lifespan of the diaphragm of the acc ball and the seals within the power piston.

If you look and compare the basic design facts of a vacuum system to the P/M, it is impossible for a vacuum brake system to outperform a proper functioning P/M. Vacuum systems have to build pressure from nothing to high enough positive pressure to move the brake pads against the rotor. The P/M has over 650psi available to stop your car the instant your foot touches the pedal. Reaction time is no comparison.

I agree that these rebuild units can be questionable. I have dealt with one (finally) and questioned the condition of the pump/motor. BUT, after properly bleeding the system upon installation, it will literally "throw you through the windshield". Ask garyk1970. He won't forget to put on his seatbelt again!

This debate will rage on.
It's good to have varying opinions and thank God we can take part in a discussion where we can discuss this. Point is to each his own. Regardless of the type of brake system you choose, it should always be properly installed, never neglected and properly maintained. No skimping allowed. Used parts should never be considered. The ability to "lock up" the tires should not be considered because locked up tires don't stop a car.

The only drawback I have been able to determine (considering the entire system) on our Buicks is the rediculous little disk brakes that those d@mn GM engineers decided to use. And there is a viable solution for that.

 

[back in black]

So if i convert over to a vaccum setup can i use the same proportioning valve or do i need the one out of the donner car.

 

[J-B Racing]

Has anyone tried a simple manual brake MC? No fuses, no vac, no worries

My wife will be driving this car, brakes Must work, always.

Rich

I was*thinking of this at one point, but I don't think you will get close to the amout of Pressure the Pm will give you...
But like you say, it will never let you down..:smile:

 

[Bweavy]

You're right the PM was designed for a non vacuum situation, however, it was not designed to work if/when the stupid 30amp fuse blows Design flaw?:wink:

The reason the 30 amp fuse blows is the motor is worn out. No different then a drill motor that goes bad.As it goes bad it draws more amps smokes etc..

 

[Bweavy]

So if i convert over to a vaccum setup can i use the same proportioning valve or do i need the one out of the donner car.

You can use the same but recomend a Brass unit. That was a factory re-call.
Unfotunately GM discontinued them this year.
An Iron proportioning valve is what causes damage to the brake fluid & power master.
I'm not saying a power master is the best unit ever produced but it was produced for a reason.

We are trying to get some one to manufacture the brass valve but have not had any luck. If any one knows a company that could do it please e-mail or PM me.

 

[Danster]

Manual Brake Kit for G-Body GM Cars

I am intrested in a manual brake set-up as well. Sometime around 1978-1981 manual brake were avaliable on the Chevrolet g-bodys. The master cylinder can be purchased at local parts stores no problem. I can't find a manual brake car in the junkyard to get the pedal and push rod. I think the push rod is unique the the manual set-up. I am not sure about the pedal.

I don't have the kit but have been thinking about it.

Drag Race Brakes

Dannyo

 

[87GN]

Where can I get the TTA check valve?? Is there a part number??

Nic

 

[Bweavy]

Where can I get the TTA check valve?? Is there a part number??

Nic

GBodyParts.com Online

 

[87GN]

All I see is the vacuum block. I'm refering to the check valve on the booster.

Nic

 

[turbo nasty]

To hit on maint and service the PM again.

A simple test that will tell you if its working right or condition its in.

Pop the hood

IGN sw off pump the brake pedal until its hard ( about 10 times or maybe more)

Turn the ign sw to "run" no start/crank position

PM will/should energize, The brake fluid level in the reservoir closest to the engine should be pulled down to around a 1/4" in no longer than 10 seconds.

If this does not happen then something is not right pump or internals or something.

I wrench on GN's frequently that the owner feel as though the PM's are working fine when driving around and they FAIL this test and then I bring it to the owners attention and they say why its working fine, I am not getting a brake light and its stops as good as ever.

Then the next thing I know their brakes go out w/o warning or they get a brake light, motor wont shut off, etc.

Sure the PM could go out even if they pass the above test its a mechanical man made part.

I have had vac brake MC's go to the floor in traffic and would not pump up with out a sign of leakage on the firewall .......they all can fail!

Keep and eye on it and learn how the system works. Main reason most swap is for money it takes on parts and service for the PM.

Not say that switches wont go out, accum go bad, and other parts.

All in all i believe if more folks had a better understanding of what to check and how it works then it would probably save some heartache...but not money.

The PM is an expensive sucker

My 02

 

[little]

Good info Nasty! I'll be checking mine this weekend.

 

[turbofish38]

Thats BS on the TTA check valve. It's the same one used on every Camarobird. It's also the same one used on NA G-body.

The only difference I've seen on check valves is the size of vacuum hose used. The stock size is 3/8 and most of the newer vehicles use 1/2". IIRC the nipple on the stock TTA vacuum block is 1/2. I've been using the stock plastic vacuum block for a long time with the 3/8 hose swedged on.

GM Part Numbers
3/8 check valve 18021981
1/2 check valve 18022219

You know it's kind of a moot point when this type of discussion comes up. There are very little parts to rebuild the PM and a reman'd unit is expensive. Both have their merits and they also have their faults. IMO the PM is the only way to go if you drive your car at 110%. And who does that? Go with the vacuum if your car is a DD or sees limited track time. There are ways to drive a TR fast with vacuum brakes. It just takes time to learn how. About 11-12 seconds for most of us.

 

[BlackBandit]

I went through two PM's. The second unit was remanned, clean fluid, passed the pump test, failed in a matter of months. Luckily that time I was at a red light. Just sitting there and then the pedal hit the floor and I started rolling. I like the performance of the PM when it works but I'm running the vac setup until I get a hydroboost system. Brian, you're right about the fuse but don't forget there's a big difference between a drill motor taking a crap while I'm drilling standing still at my work bench and my PM motor going bad trying to haul 3500 pounds from 60 to 0 in a panic stop. Plus, if you're really worried about the reaction time you can set up a system that uses engine vacuum and get an auxilary vacuum motor and a resevour coupled with a good check valve and you'll never have a hard pedal. That way there's also a little redundancy.

 

[Bweavy]

All I see is the vacuum block. I'm refering to the check valve on the booster.

Nic

Check valve is $14.00 I'll get it back up on the site tonight not sure what happened to it.