Brake Master Cylinders

[Jared Richey]

Ok, I need some help here.

 

Its something to me that seems like common sense.

The car is a friend' 71 Buick Electra 225 with power disk brakes front/ drums rear like our cars.

His brakes tore up the other day so I told him to come over here and we'd go ahead and replace the master cylinder. We take it off and its a DEEP BORE master cylinder, the Problem is the Power Booster has the short plunger, so shouldn't the car have a SHORT bore Master Cylinder as well?

 

The Napa tech guy is saying it should have a deep bore one, although it shows 2 different master cylinders and Power Boosters for that model year, one the pushrod on the boster sticks out almost even with the studs that hold the MC in place, the other like on my friend's car has a short push rod like on our Montes. Why would a Short Push Rod Booster call for a DEEP bore MC????

 

My hypothesis was that someone had put the Wrong MC on his car years ago when his now deceased Mom drove it everyday, but the brakes worked good with the deep bore (till it went out the other day) and it works good and feels right with this one.

[Andreas]

Not sure I understand. How did the short push rod actuate the Deep Bore MC?

 

As far as I remember, you can use either (probably with some sort of pushrod adapter) with power brakes, but you should NEVER use a shallow bore MC with Manual Brakes.

[Jared Richey]

Not sure I understand. How did the short push rod actuate the Deep Bore MC?

 

As far as I remember, you can use either (probably with some sort of pushrod adapter) with power brakes, but you should NEVER use a shallow bore MC with Manual Brakes.

 

That's what I didn't understand how it was even working. Now the car has what seems to be the correct MC to me, a shallow bore one, with the short Booster Push Rod.

Napa techline was telling my friend it should have a deep bore one with the short booster rod??? Said something about something they did in 71 and 72 with those cars.