Brake question

[Herr Otto]

My truck is getting closer to being able to do a true road test but I have a question about the brakes. I switched to a dual chamber master cylinder. When driving forward down the side street and braking, the truck stops fine and straight. When going in reverse and braking, the truck almost pulls the steering wheel out of my hands and feels like the front brakes are doing all the work. I followed all instructions on adjusting the brakes and the system has been bled. Any suggestions or comments?

Thank you,

Otto

[Frank Elder]

Did you put 2lb residual valves in the front, and 10 lbs in the rear? That will help them brake correctly....also I believe you are supposed to remove the residual valve that is attached to the MC also, someone please chime in.

[Herr Otto]

I did not put any valves in just the dual chamber master.

[lugnut123]

do you have the original axels still on your truck?

[NiftyFifty]

Like the last post..if you have your original axles then you have to get an adjustable valve (Summit racing or other spots should have) or if there are inline smaller set valves those would be an option too. I swaped in a dual on mine, but I also went to front disc and a rear diff from basically the same vehicle.

[lugnut123]

One of my old trucks I tryed to put a newer dual M/C in without any valves. I piped the outlets together then to the wheel cylinders and couldn't get the M/C to work. I finally went back to the original equipment and to works now. Maybe if I had ran it through a porpotioning valve it would have worked?

[NiftyFifty]

One of my old trucks I tryed to put a newer dual M/C in without any valves. I piped the outlets together then to the wheel cylinders and couldn't get the M/C to work. I finally went back to the original equipment and to works now. Maybe if I had ran it through a porpotioning valve it would have worked?

Ya, best to keep the valve that came off the same vehicle you got the MC from...seems to work pretty goon on mine....and some I think are even adjustable

[Herr Otto]

I have the original axles on the truck. I will look into an adjustable proportioning valve. Is there one for the each the front and rear?

Otto

[Dave72dt]

No, just one. Both lines from the master feed into it and lines go out to the front and rear axles.

[NiftyFifty]

No, just one. Both lines from the master feed into it and lines go out to the front and rear axles.

Should have 3 ports no? I know the stock prop valves do....2 fronts and 1 rear

[Dave72dt]

He went to a dual chamber MC which means he will have two lines coming out, one for the front and one for the rear. These lines need to go to the proportioning valve which often contains the compensating valve. They then go out to the axles through 2 or 3 ports.

[Herr Otto]

I put the rearend up on jackstands and ran the truck and found out that my rear brakes will not stop the wheels from spinning. I re-adjusted the rear shoes to the point where they are almost too tight and the rear wheels still will not stop. I re-bled the system with no change. Do you think it is possible that I have a bad (rebuilt) master cylinder?

Thank you

[Dave72dt]

Sounds like you need a check valve in the rear line to keep the linings from retracting to far.

[Don Coatney]

I recently installed a dual master cylinder on my car. I had lots of problems. The link below details all my problems and may be of help.

http://www430.pair.com/p15d24/mopar_forum/showthread.php?t=22469

Your fix may be as simple as adjusting the length of the rod that feeds your master cylinder.

[suntennis]

Did you replace or check any of the rear wheel cylinders to see if the pistons move or if they leak? If you bleed the rears, there is fluid to the cylinders, but if they are frozen, they will not work. Other comments are about proportioning valve as if you put disk brakes on the front. When I replaced a master cylinder on a newer car where it is mounted on the firewall, it was necessary to bleed the master before install. If the cylinder is mounted below the floorboard, maybe this is not required.

Edited September 27, 2010 by suntennis

[Herr Otto]

I have the original drums in front and rear. The master cylinder is mounted on the firewall. I will check, but I do not believe there is any adjustment in the rod. It sounds like I may need a hold off valve and/or a residual valve.

[Merle Coggins]

Do you have a solid pedal or does it go to the floor? If the pedal is solid and the brakes won't stop the wheels, but you can get pressure out when bled, I'd have to say that your brakes are seized up and not expanding into the drums. If the pedal goes to the floor and the brakes don't hold, then the problem is either still air in the lines or something is out of adjustment.

Merle

[Don Coatney]

I have the original drums in front and rear. The master cylinder is mounted on the firewall. I will check, but I do not believe there is any adjustment in the rod. It sounds like I may need a hold off valve and/or a residual valve.

Can you post a picture of your new firewall mounted master cylinder? What is the bore size of your new master cylinder? Did you buy this new master cylinder as a kit designed to be used with stock drum brakes on all 4 wheels?

[Merle Coggins]

I believe he bought this truck as an unfinished project and he's working through all of the unfinished issues. Hard telling what that master cylinder is from.

Merle

[Herr Otto]

The master is from a 1970 Dodge D100 pick up truck. I returned it today and got a replacement which strangely is the same part # but looks nothing like the one I took off. I bench bled the new master and installed it. The pedal is not solid at all, though the bench bleeding went well. When I get an asssistant I will bleed the system again.

[Don Coatney]

The master is from a 1970 Dodge D100 pick up truck. I returned it today and got a replacement which strangely is the same part # but looks nothing like the one I took off. I bench bled the new master and installed it. The pedal is not solid at all, though the bench bleeding went well. When I get an asssistant I will bleed the system again.

What is the bore size of this master cylinder? Have the brakes setup with this master cylinder ever worked? Is there enough travel with your swing pedal assembly to move the master cylinder piston a full stroke?

[Herr Otto]

I have no idea of the bore size. I never had the truck lifted to see if the rear brakes were actually working correctly. I was able to go down the road at 60mph and stop with this set up, though when backing out of the garage it did feel like the front brakes were doing all the work.

This afternoon I bled the system with the new master cylinder and the rear wheels still will not completely stop when lifted off the ground.

At this point I wish I could just go back to a single cylinder master cylinder but I am not sure what one to get because the brake pedal has been changed and the master needs to be mounted on the firewall.

Thank you

[Don Coatney]

Pictures of this install would really help.

[Don Coatney]

And as I mentioned above read this link.

http://www430.pair.com/p15d24/mopar_forum/showthread.php?t=22469

I just went through this and hopefully some information on this link may help to resolve your problem.

[Herr Otto]

Don, thank you for the reply. I did read your link and see that you had somewhat of a similar problem. There is no adjustment in my brake pedal rod. I will re-read your link to look for more helpful info.

Thank you