Power Brakes Going Out

T

TulsaGN13

Member
Joined
Jul 2, 2010
I have an 87 GN with 107k miles and stock brake setup. Recently I am losing the power assist on the brakes intermittently. When it happens, the brake light comes on and the power assist fades in and out. When the car is cold the power assist works just fine but after about 15-20 minutes of driving the car the brake light comes on and the power brakes are a coin toss. The longer I drive, the less likely I am to have any power assist at all.

I know that powermaster brakes are notorious for having problems but I have also heard about people having problems with the vacuum conversion. I plan to eventually install an entire aftermarket 4-wheel disc conversion but I can't afford it at the moment. Could anyone point me in the right direction to start diagnosing the exact problem. I can't afford to just throw parts at it.

Thanks,
Bill
 
Dont see why their would be any issues with vacuum brakes if they were installed correctly look at all the cars that came with them. But If you want a guaranteed to work all the time system go manual.
 
The complaints I read about vacuum were mostly about them not holding well when you are trying to build boost for a launch. At the moment I am hoping I don't even need to consider that as an option. I have priced conversion kits and I am hoping to fix the current problem with my brakes for less than it would cost for a conversion anyway. I need to go the cheapest route possible to fix my car for now.
 
First thing I would do is replace all the brake fluid. I started getting an intermittent brake light about 8 years ago. I got another 5 or 6 years out of the accumulator before the light started coming back and I replaced it.

David
 
Great idea David! There is no telling how old the brake fluid is in that car. I probably should have done that as part of my spring cleaning anyway.
 
I had a similar problem about three years ago. Switched to the vacuum brake set-up from a Monte Carlo and have had no problems since. I am still running drums on the back, so I can't comment on how it would work with discs all around. The hardest part with the swap was finding the pedal assembly.
 
Thanks for the info! I decided to go ahead and flush the whole brake system today. I got it up on jack stands and the wheels off and was just about to get started when something caught my eye at the back of the master cylinder. It is definitely losing fluid. Well, now I know that's at least one part that needs to be rebuilt or replaced. I will start there this week and see where that leads me.
 
I ended up doing the conversion to vacuum brakes yesterday. It was relatively easy. The most difficult part was reinstalling the bolt at the top of the vacuum brake pedal. I haven't bled the brakes yet, so it is a little spongy, but on my first few tries it is holding up to about 7 lbs of boost on a launch.

I followed the instructions from GNTYPE.ORG found here http://www.gnttype.org/techarea/brakes/Powermaster_to_vacuum.html

Overall I am very pleased with the conversion and I highly recommend it to anyone looking at a more reliable replacement for the Powermaster.

Thanks for the help and advice as always!
Bill
 
I'm happy with mine. I've held 9 pounds on launch. Does this mean you will be coming out to Cruise Night at Fuddruckers this week?
 
Yes, I will be there this week at around 5:30 in the T-top 87 Grand National that is my avatar. It definitely isn't a show car, but it is in decent condition for a daily driver.

I am hoping that once I bleed the brakes I will be able to hold a little more boost on launch. I also need to look into getting a line lock. I have never used one, so it is time to start doing some research.
 
Hey guys, I totally agree with you on going to the Vacuum Brakes,,I totally dont know why I didnt do it years ago...
By the way here is also another source for info. This guy even shows you were you have to drill a hole to relocate the bolt instead of getting a Vacuum Brake Pedal. I just blew the drawing up and measured,,no problems at all..Hope this helps, his site is
http://tomsttype.com/
 
You must log in or register to reply here.

Similar threads

NoVA_87_GN
Bleeding Front Brakes
Replies
4
Views
804
NoVA_87_GN
NoVA_87_GN
X
Cant bleed brakes right
Replies
8
Views
1K
earlbrown
E
RezVek
Powermaster Issues
2 3
Replies
54
Views
5K
RezVek
RezVek
B
Vacuum booster/ master issues.
Replies
9
Views
1K
BADASSOMAR
B
VtheGNMan
Front Brake upgrade to Wilwood 140-12837?
Replies
7
Views
2K
VtheGNMan
VtheGNMan
Top