Brake Problems

[John Burke]

The brakes on the 49 Dodge have started acting up. To explain my set up...I have a "Cuda" rear end of about mid 60's vintage and a firewall mounted, dual chamber master cylinder with a swing pedal. The pressure in the rear brakes gradually builds up, 20-30 miles of driving, till the pedal is hard and the rear brakes are not releasing. When I stop, the brake light stays on and after an hour or so the pressure gradually releases and the light goes out. The next morning the brakes act fine at first but the problem reapppears when driving it. Most of the locking up seems to occur in the passenger rear wheel so I tore it down and replaced a leaky wheel cylinder, and a worn axle bearing and seal....This did not solve the problem. It's going to my mechanic next week but he will be digging in the dark also. Any suggestions would be helpful...btw the power steering from a 70's GM I added works great. Speedway now has a nice, all electric, unit that would probably be easier to install but they start at a grand.....jb

[PatS....]

I would be looking at the flex hose going to the rear end, then for a kinked line going to the rear end, not allowing the fluid to return to the master properly.

[martybose]

Aren't the symptoms he described typical of a master cylinder pushrod that is too long, thereby covering up the port to the master cylinder reservoir?

Marty

[Andydodge]

John, what sort of front brakes do you have?.......if you have discs then you should be running a pressure limiting/residual valve on the rear lines, as most dual circuit master cylinders will either have one built in or there would have been one on the original rear line to the Cuda rear end, as discs use much higher line pressure and rear drums without the valve will lock up. If you have drums all round then is the master cylinder from a disc brake system?......as again it would have higher pressure then an all drum brake system cylinder........andyd

[Plymouthy Adams]

Actually the power brake booster is normally the larger bore..(1 inch) less pressure applied than the typically non powered manual bore...(7/8 inch) the larger bore will indeed give you a tighter pedal but..should never interfere with the brakes in such a way to lock them up.

[John Burke]

Aren't the symptoms he described typical of a master cylinder pushrod that is too long, thereby covering up the port to the master cylinder reservoir?

Marty

Marty....it appears you had the answere...I shortened the master cylinder pushrod about 2 turns and got more freeplay on the pedal. A 30 mile test run last nite showed no problems so we may be good to go....I'll give it a few more runs today increasing the distance before I take a long trip....btw the power steering is working like a champ.....thanks for the tip Marty.....John

[John Burke]

Well I spoke to soon....I started out on a run tonite and was forced to turn around and go back... My expensive "Vintage Air" conditioning unit quit cooling also...Temp read 100* on the Wahoo bank...needless to say i was not in good humor. I'll check the lines tomorrow and if I don't find anything wrong I'll try a new master cylinder....jb

[Frank Elder]

I see your on line John, did you ever get your brake problem solved? What was the mystery malfunction?

Fellow Nebraskan FRANKIE47