Difference between Wagon Powermaster and GN Powermaster?

[DMan]

Way way back, I bought a rebuilt PM for my car from an autoparts store. I installed it - it worked ok but the pedal always felt soft. I bled the brake lines and PM and still it felt soft. oh well - decided to live with it. It looked a little different than my original PM. It had a tapered fluid reservoir.

A few years ago, I learned that the powermasters for wagons are different. It has some different hard parts inside that alter the brake feel - so I learned from a 2003 powermaster tech session at the Nats. Also, you can always tell a PM that came off wagon because it has a tapered fluid reservoir. At that point I realized I have one of these wagon PMs on my car. I didn't know any better when I bought it.

Can anyone here confirm that a wagon PM definitely alters brake feel? What specifically is different about the parts inside?

 

[POWERBRAKEBOB]

Hydroboost Conversion

The Units Are The Same Except For The Reservoir, The Mounting Bracket, And The Pedal Rod. The Difference In The Angle Of The Bracket, And The Length Of The Pedal Rod Would Alter The Feel. You Would Need To Use The "regal" Bracket And Rod.

 

[turbofish38]

Yep there is also a different size primary piston. I dont think it has anything to do with pedal feel or operation though. Here's a quote straight from the FSM.
"Make note of the primary piston identifaction, stamped on side of piston, and piston length (E-11,108.08mm or E-14,105.28mm). This is to assist in selecting the correct replacement primary piston assembly. Failure to use the correct piston will result in defective brake operation"

I have had many PMs apart in the last 20 years or so and the wagon uses the 108mm piston IIRC. I know I've tried both of them and didn't notice any difference between the two. You can also ID the correct push rod. There is a letter stamped on them. B is the wagon part and its either "A" or "G" for the TR part. You can swap the rods as they are only held on by a C-clip. I've always left the bracket bolted onto the firewall when servicing the PM. Just remove it like a normal MC. And of course the reservior interchanges just as easily.

If it was me, I'd hook up the gauge to confirm that the pump is pushing out enough pressure before I'd condem a PM because of a mushy pedal. I used to abuse the heck out of a PM doing open course events. I could always tell if a pump was down a couple of hundred PSI by how firm the pedal was after I flushed the system.

 

[DMan]

Now that there is a QUALITY post. Thanks Eric!!

 

[DMan]

Eric, if your PM was a couple hundred PSI low, wouldn't it set off the pressure switch/brake light on the instrument panel?