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brake pedal falling #1323745 10/21/12 11:20 AM 10/21/12 11:20 AM
Joined: Jul 2009 Posts: 198 Staten Island, NY T Theorio1025 OP member
Theorio1025 OP member T Joined: Jul 2009 Posts: 198 Staten Island, NY	I have a 69 roadrunner with front disc rear drum using the 73-76 a body setup. I was driving a week ago and the pedal started to fall when I hit the brakes, and the brake light would turn on. I drove it home, and checked for brake fluid leaks. There were no external leaks I could see. The symptoms appeared to be a bad master so I ordered a new one, and put it in. After bleeding the master the pedal is firm with the car stopped, but as soon as you drive one or to stops in the pedal will fall and the light comes on. It comes and goes but its hard to stop the car when its doing it. Anyone have this happen before?

Re: brake pedal falling [Re: Theorio1025] #1323746 10/21/12 01:18 PM 10/21/12 01:18 PM
Joined: Jan 2003 Posts: 21,067 Niles , Ohio T therocks oh wait.but hey.lets see.oh yeah.
therocks oh wait.but hey.lets see.oh yeah. T Joined: Jan 2003 Posts: 21,067 Niles , Ohio	Are the rears adjusted up?That will cause it at times.Power or manual brakes?Does it do it if you dont drive but just apply pressure to the brakes and does the master get low?Pull the drums and check the wheel cyls.Rocky Chrysler Firepower

Re: brake pedal falling [Re: Theorio1025] #1323747 10/21/12 11:17 PM 10/21/12 11:17 PM
Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska	Sure sounds like the M/C went bad as you surmised and one side has to have way lower pressure for the light to come on but from your descrip it is a part time problem that comes and goes . I suppose it is possible that the rebuilt M/C is bad. I'd give it another good visual from head to toe & have a helper work the pedal with you underneath & I'd cap the M/C with a pair of brass inverted flare plugs from the "Edelman" fittings cabinet at your parts house & if the M/C is good and bled out with it capped it will be rock hard with virtually no travel & stomp it hard and try with light pressure & see how it acts. Holler how it goes. live every 24 hour block of time like it's your last day on earth

Re: brake pedal falling [Re: RapidRobert] #1323748 10/22/12 01:17 AM 10/22/12 01:17 AM
Joined: Jan 2004 Posts: 27,347 Today? Who Knows? 1_WILD_RT Management Trainee
1_WILD_RT Management Trainee Joined: Jan 2004 Posts: 27,347 Today? Who Knows?	Sounds very much like a bad master cylinder... Hard pressure on the brake pedal usually gets a solid pedal but light pressure will let the pedal sink to the floor... I agree plug the ports & see what it does.. If the pedal still sinks under light pressure than the M/C is junk... "The Armies of our ancestors were lucky, in that they were not trailed by a second army of pencil pushers."

Re: brake pedal falling [Re: 1_WILD_RT] #1323749 10/22/12 12:22 PM 10/22/12 12:22 PM
Joined: Jan 2005 Posts: 3,344 Central TX roe master
roe master Joined: Jan 2005 Posts: 3,344 Central TX	Definitely don't re out a bad master cylinder right out the box, I've had it happen to me before with a master cylinder and alternator. 1971 Plymouth Satellite 408/904 8 3/4 3.23 SG

Re: brake pedal falling [Re: Theorio1025] #1323750 10/22/12 01:43 PM 10/22/12 01:43 PM
Joined: Mar 2008 Posts: 5,746 Ontario, Canada Dodgem master
Dodgem master Joined: Mar 2008 Posts: 5,746 Ontario, Canada	I concur sure sounds like a bad master. mexican rebuilds are not all that cool sometimes.

Re: brake pedal falling [Re: roe] #1323751 10/23/12 02:59 PM 10/23/12 02:59 PM
Joined: Jan 2003 Posts: 2,931 P Paul_Fancsali master
Paul_Fancsali master P Joined: Jan 2003 Posts: 2,931	Is the fluid level still full in replacement master cylinder ? If not make sure the fluid bleeding did not knock out wheel cyliner / caliper

Re: brake pedal falling [Re: Theorio1025] #1323752 10/23/12 04:33 PM 10/23/12 04:33 PM
Joined: Feb 2003 Posts: 1,142 Tucson, AZ C cruzin super stock
cruzin super stock C Joined: Feb 2003 Posts: 1,142 Tucson, AZ	Are you using an adjustable brake pedal rod? I had a similar experience with my adjustable brake rod loosing it's adjustment which resulted the same conditions you are experiencing. Regarding the brake light. This is related to the pedal making contact with the switch (i.e. pedal dropping) I believe.

Re: brake pedal falling [Re: Theorio1025] #1323753 10/23/12 10:29 PM 10/23/12 10:29 PM
Joined: Aug 2003 Posts: 43,157 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,157 Bend,OR USA	Quote: I have a 69 roadrunner with front disc rear drum using the 73-76 a body setup. I was driving a week ago and the pedal started to fall when I hit the brakes, and the brake light would turn on. I drove it home, and checked for brake fluid leaks. There were no external leaks I could see. The symptoms appeared to be a bad master so I ordered a new one, and put it in. After bleeding the master the pedal is firm with the car stopped, but as soon as you drive one or to stops in the pedal will fall and the light comes on. It comes and goes but its hard to stop the car when its doing it. Anyone have this happen before? If your car was a original drum brake car front and rear did you add a proportioning valve and remove the residual valve in the master cylinder for the new front disc brakes? If not you should Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

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