Bad Master Cylinder or Air?

[moparstud440]

Just wanted to give an update on this. I bought a vacuum bleeder and finally got around to bleeding the rear brakes today. I did both the passenger and driver side. I pulled the fluid from the front reservoir to about 1/2 way twice for each side. Had a good steady stream of fluid and didn't notice any air even when I first started. Pedal still felt the same. I tried the items AJ/FormS suggested for the hydraulic portion and the pedal never was able to get a hard pedal. The hoses up front are new (doesn't mean they are good, as we've all bought new items that ended up being junk..) When bleeding the front the pedal goes to the floor so I believe it's a rear brake issue. I did replace the rubber line to the rear end housing 2 years ago when I first got the brakes working as the old one was clogged. Found that issue since I couldn't get any fluid to the rear wheel cylinders. I'm 99.9% sure it's a master cylinder issue so I've order another one to see for sure and than will have the one on the car warranty if that is indeed the case. With the virus stuff going on it's hard to find parts at the moment. Hopefully the new master cylinder will be here this week and I can get it cleaned up and painted, bench bleed and installed. Will report back later.

 

[moparstud440]

I received the new master cylinder on Friday and got it painted, bench bleed, installed on car and than bleed each wheel several times. Pedal felt a little better but was still soft. Back when I first starting messing with this issue I took my the brake rod off my 1975 Duster to measure since it has factory disc, etc. It measured 1/8" longer than the one on my Cuda. Lots of people say that the manual rods are all the same or work.. I figured being only 1/8" shorter it should be okay, just was the variance in production lines back in the day or they changed them a little bit from 69 to 75. Anyways I bought a adjustable rod when I got the 2nd new master cylinder just in case to try. Well I adjusted the new master cylinder rod to the same length as the one in my Duster and now the pedal feels like it should. I took the car just for a trip out the driveway and back (I have a LONG driveway) and I am now able to lock up the wheels. I would never of thought the 1/8" difference would've made that much difference, but it sure did.