Ok I finally got my 1969 GTS. Drove it home yesterday from Orange CA to San Diego.

Long story short the Master Cylinder is going. The usual slow drop to floor symptom. No leaks, hard pedal, but hold the pedal and in about a minute the pedal is too the floor.

Stock brakes. Disc/drum. New lines from the rebuild.

So here is my question. What is the best route to buy a new MC? Do I go with pre 1975 or go to the later aluminum unit? Also I found these on ebay. http://www.ebay.com/itm/320938392214...S:1123&vxp=mtr


The way these are described, the pre 75 brakes on mopars all had a special valve in the MC to deal with the originally designed brake cylinders. My question is are the original calipers also designed to require the MC that has the valve? I am going to stick with manual brakes for now, so I also need to make sure I get the right MC cuz discs require higher fluid pressure than drums I am told.

I need to address this before I feel safe to go cruising. Not fun hitting the brakes and have the pedal go nearly to the floor.

Thx in advance

Oh and speaking of advance, I also have a pinging problem. I will post a thread in the engine section.

 

The link is to a set of wheel cylinders. Usually the problem wheel cylinders are used IF you have a problem with the wheels locking when stopping hard. The valve in the master cyl is for drum brakes only- retains a small pressure in the system. Not needed on front with disks. If you have disks almost any of the newer master will work. If you still have drums you need to make sure it is compatible with drums.. I would not use the aluminum master if you have headers. My personal feeling is the heat could damage the plastic fluid reservoir

 

TVLynn,

I do not have headers yet. I will keep that in mind though. And the description re those cylinders mentions spongy pedal. That usually means air in the line or negative pressure. I am assuming that new style MC with old style original rear drums allows negative pressure to build as brake shoes wear. Sounds like in the original MC there is a valve that keeps that negative pressure from building up. Maybe I am reading this wrong?

I am just not sure if the original Disc set up I have on the front would also be subject to the same affect if I am correct in my interpretation on what is referred to spongy pedal in the ad.

Tom

 

i have run the aluminium/ plastic reservoir with headers in a diplomat never had any issues
or go with oem replacement part
or if you can chaching the go with a after market setup with adjustable proportioning valve that fine tuning could be the ticket
summit racing has a nice selection check em out

 

I think I have a similar problem. I have a 69 Roadrunner, don't know too much about it's history. The previous owner died. When I try to stop or slow down the pedal goes all the way down after about 30 seconds. It takes me way too long to stop. The fluid is topped off, it looks like the original master cylinder. I don't see any leaks on my garage floor. Where do I start troubleshooting? I plan on getting discs up front anyway.