1970 D26 Winnie Brake Problem

[Ramblen Ron]

Hey Fellas and Gals,
Been awhile since I visited this neck of the woods. Late start opn working on my Ramblin Rose.  I have been plagued with problems, it seems, from fuel issues now to brakes.  Does anyone have an idea as to what is happening when I start the engine and my brakes go on?  I suspected the fron rims were getting hot and the rig had a tendency to not move when I put it in gear. It would go after I stepped it down but I was unaware what was happening till I checked things out.  With the engine off the wheels turn fine.  Start the engine and the brakes are on.  I don't know a thing about the power booster and how they work, I know there is a big Vaccum line going back to the booster.  HELP!!!!!!!!!!!

[DaveVA78Chieftain]

First you need to know if you have a M300 or M375 Chassis.  Because the service manual is a bit confusing to determine what information applies to a given configuration, I have assembled a some pages that tie information for the respective components together for different configurations.

69-71 M300: http://dave78chieftain.zxq.net/M300_69-Early.html
69-71 M375: http://dave78chieftain.zxq.net/M375Early.html

It is mostly nothing more than reprints from the manual.  There a links on each page to the relative information for each configuration.  The boosters are different for each configuration however the troubleshooting information applies to both types.  I see I have a coding error for figure 2.  It is supposed to be the main drawing for the M375 configuration (same one as at top of M375 page).
The site is still a work in progress for the parts.  If you need help with identifing parts let me know.

Dave

[Ramblen Ron]

Hey Dave,
Through trial and error and talking with the parts store I figured it out to be the forward booster has a leak in the vacuum.  I disconnected it and my problem went away.  The diagram for the 300 is the one I have and it appears the front runs the front and the rear booster is for the back. ?

[DaveVA78Chieftain]

My best guess,
Look at the Failure to Release portion of the Midland-Ross Service Diagnosis table in the Service manual.
http://dave78chieftain.zxq.net/MidlandRoss.html

Sounds like the control valve is stuck.  You can get a booster at Precision Rebuilders or NAPA.  Scroll down to the parts section on the M300 page for booster information.

With the vacuum line to the front booster disconnected you may only have rear brakes.

One booster for front and one for rear was typical for that era.  Early years used the Midland-Ross booster until they went to the Hydro-Vac unit.  They finally went to a Hydro-boost system in 1979 which is driven from the power steering pump.

Dave