I'm considering converting my car to vacuum brakes. Went to the parts store to price out rebuilt vacuum booster, master cylinder, etc. The counter guy asked me whether I wanted a single or double diaphragm vacuum booster. Which is recommended? Is more better in this case? Which one came standard on non-turbo cars? Does it matter?
you want the tandem which is 9" in dia. Tandem mean double.
Thanks Frank for the quick reply. I'm off to the parts store!
OK guys, went to the yard yesterday and got a pedal out of a mid-80's Monte SS. Went to the parts store, Consumer Auto Parts (C.A.P.) and picked up my re-man master cylinder and vacuum booster (Cardone). Total cost: $26+$5 core for the MC w/reservoir, $95+$10 core on the tandem booster, $10 for the pedal (plus the two under body front braces) on the Monte SS. A few hours of BS&T hanging upside down in a couple of G-bodies. Installation complete! It really was easier to put it together than it was to take it apart! It was so hot in the junkyard I burned my fingers putting the tools back in the box when I was done! I followed the bench bleeding procedure for the master cylinder that came with the unit. Put it in a vise and pushed the plunger many times until no more bubbles. Installed it in the car, checked the pushrod length. I have about 3/8" pedal travel before it moves fluid which should be OK. Connected the brake lines to the MC. My lines were not even close to where they needed to be, so I bent them enough to fit. Connected the vac line. Started the car and tried the brakes to see how bad they needed to be bled. While looking at the master cylinder when pushing the brake pedal, I could see a lot of bubbling in the rear MC reservoir. Brakes are SUPER SPONGY! Do I need to re-bleed the MC before going any further? Should I just forge ahead with the rest of the bleeding procedure? Can the MC be bled properly in the vehicle or do I need to pull it back out and re-do the bench bleed? It sits on an incline when installed. Any ideas?
I think you get a better feel of pedal sponginess when you check it with the motor off and the vacuum system depleted. Try to get as hard a pedal as you can like that, then see what it's like with the car running.
i wish that conversion kits would be more specific about the single or double diaphragm system... which one is it??
First I have to start by saying that I have only owned my 87 GN for 5 months. I have dreamed about owning one since 1986. My car is fully restored BUT I am experiencing problems with the powermaster system. I returned it to the dealer (because the previous owner owns a GM dealer and had it fully restored at his shop) to replace the brake module. Well it has been replaced 3 times and I still have no brakes. I decided to do some research and found that the powermaster system is junk.. So I am going to convert it but I really need to know if I need a single or double diaphragm brake booster for the car.. No one at the dealer seems to know a thing about it. I thought that they would be smarter than that, apparently NOT!!!
I don't think you've researched the topic enough to call the item junk. I've had my car for four years and while I did have to replace my powermaster unit and even had to return the reman'd unit I recieved once, I don't think it's a junk system. The reman'd unit was reman'd bad and the proper parts weren't replaced. I would try to use the troubleshooting charts on the website to determine where your problem lies. You could have a simple problem such as air in the lines. And you have to remember, these cars ARE old and you might not have anyone at that dealership who knows how to work with that system. This isn't a flame towards you, I'm just trying to open your eyes a little and hopefully save you some money. Like I said, it may be something small and inexpensive, especially if the car is restored, and no use spending all the time and money to convert it if you don't have to, not to mention take away from the car's originality. The power master vs vacuum brake debate is a very old one and it always ends up coming down to the individual. Good luck.
It may not be proper to call a Powermaster "junk", but certainly UNRELIABLE would fit! Yes, some owners have an original unit and may have only replaced a couple parts on it. It is not a question of "if" it fails, but "when"? There is not a good time. I know of only one case that sudden PM failure has caused a collision, know of lots of close calls.
That alone is reason enough to condemn this brake system. Bet the Chev, Ford, Mopar and any other brand does not have the traffic in discussing their brake failures? They use a vacuum system like my '72 Riv, still with the original booster.
Just tell the dealer to forget you have a turbo car and install the same booster, master cyl and pedal as in a non-turbo '87 Regal. Maybe they can figure that out? If not, go the the tech area and copy the vac conversion article for them.
Thanks for your response!! I don't mean to slam powermaster systems BUT I have experienced problem after problem with mine. The research that I have done-- More people than none say to change over to a vacuum system.. BUT if I can figure this problem out I just might keep it , for now anyway. The dealer.. well that's another story. The mechanic that works on mine is 51 and has worked at this place for 20 years, he seems like a real sharp guy but when it comes to my car he's just a head scratcher. Hmmm.. I understand that after talking with other GN owners that it would come down to personal preference... Hell.. I just wanna drive my car, Looks like I am going to have to take time off of work to fix this problem. The only reason I wanted to change to a vacuum system is -- From the multiple failure analysis of the powermaster system it has been determined unreliable. Maybe, maybe not. The vacuum system has been reported extremely reliable. I want to close this subject for good and never have to bother with another brake system problem similar to what I am experiencing now. As far as cost..$300 would cover all of the parts but every time I ask the dealer they say.."Well there are 2 types of boosters!! single and double diaphragm, which one do you need?" I stand there with my mouth open and say "Dah I dunno"... I have looked at multiple websites and could not find an answer.. Please help my broken GN.
Dual diaphragm is smaller and I'm pretty sure that's what everyone recommends.
Thanks Ken