Too much brake pressure

JasonNCJasonNC Expert Adviser
in HUDSON Posts: 652
I installed a brake reservoir to the firewall and for some reason the brake pedal keeps rising to the point that the brake lights come on by themselves.  I've adjusted the rear brake drums to alleviate some of the brake pressure, but when the car is car cranked and the tires engaged, the brake lights flicker.  I'm thinking I need to make an adjustment where the brake pedal rod enters the master cylinder so that the brake pedal has some travel before the brakes engage.  I don't see how that is done in the repair manual.  Right now the brake engages immediately when the brake pedal is barely touched.  

Comments

  • Oldfarmer1947gmailcomOldfarmer1947gmailcom Expert Adviser
    Posts: 1,224
    Are you running disc brakes on front? If so are you running a brake pressure balancing valve?
  • bob wardbob ward Senior Contributor
    Posts: 907
    The master cylinder push rod is a simple threaded rod with a lock nut, just back the rod off until you feel minimal clearance to the back of the piston.
    Lockyer Valley, Queensland
  • RichardDRichardD Member
    edited March 19 Posts: 384

    All I have read is that you don't need the 2 psi proportioning valve for the front if the reservoir is higher than the disk calipers. I removed the 2 psi PV when I installed the remote reservoir on the firewall. I kept the 10 psi PV for the rear.
    Just installed a Power Brake unit, PBR VH40; but am having a problem bleeding the system so I am certainly not an expert.


    1953 Hornet 4Dr 

    A/C-PB-PS-Rearcam-12v-alumrad/elecfan-WWW-visor-etc

    https://goo.gl/photos/a2dCQaWVmu1KT1QFA


  • JasonNCJasonNC Expert Adviser
    Posts: 652
    I have drum brakes all around on this car. I'm going to try what Bob said.  
  • Geoff C., N.Z.Geoff C., N.Z. Senior Contributor
    Posts: 3,186
    It is essential to  have that clearance between the  rod and the cylinder, otherwise the bleed hole is covered, leading to what you have experienced. 
    If you're stuck in a hole, stop digging.
  • JasonNCJasonNC Expert Adviser
    Posts: 652
    Ok, so I adjust the rod that goes to the master cylinder and notice afterwards that brake fluid is accumulating in the boot that covers the rod.  What is causing that?
  • bob wardbob ward Senior Contributor
    Posts: 907
    You have a leaky piston seal, time for a new master cylinder kit and maybe a hone.
    Lockyer Valley, Queensland
  • RichardDRichardD Member
    edited March 22 Posts: 384
    Jason, I ordered a repair kit from NAPA last week. They found one in Memphis warehouse. Read on site that the number is 138 for my '53. If that isn't right, guess what I am having for lunch?
     Came in today but I haven't picked up yet.

    1953 Hornet 4Dr 

    A/C-PB-PS-Rearcam-12v-alumrad/elecfan-WWW-visor-etc

    https://goo.gl/photos/a2dCQaWVmu1KT1QFA


  • FrankvintagefullflowcomFrankvintagefullflowcom Senior Contributor
    edited March 22 Posts: 924

    Jason, Richard,

    Just my opinion, but by the time you get it back together after trying to hone out the pits or having it sleeved, you'll wish you had just replaced it with a new one. The NAPA # for a new cyl. is NMC M3081 and they seem to be fairly common. Our local Po Dunk town has one and I see that there are several at the nearby distribution centers. They fit a ton of Hudsons, a few Hyster forklifts and many mid-fifties Packards.

    The rebuilt version (P3081) is shown as being much cheaper but availability is zero according to my info. Shop that number at your favorite AP Store if you don't want NAPA.

    Good luck.

  • RichardDRichardD Member
    Posts: 384
    Correct, Frank. Mine is not leaking but might not be pressurizing enough. $20. vs $100. so I am taking the chance.

    1953 Hornet 4Dr 

    A/C-PB-PS-Rearcam-12v-alumrad/elecfan-WWW-visor-etc

    https://goo.gl/photos/a2dCQaWVmu1KT1QFA


  • cardoclassicscardoclassics Expert Adviser
    Posts: 27
    bleed the brakes???
  • JasonNCJasonNC Expert Adviser
    Posts: 652
    I went to NAPA and according to the salesman, the 138 is for the 48-50 Hudson.  The kit is in Columbus, OH and not available until next week. They can have a new MC there in the morning.  I elected to purchase a new MC as opposed to rebuilding a part that may be over 67 years old.  
  • FrankvintagefullflowcomFrankvintagefullflowcom Senior Contributor
    edited March 22 Posts: 924

    Bingo! We have a winner!

    You won't regret going that route, especially if you don't have much/any experience with such repairs.

    I think they're off base with the '48-'50 kit application but it doesn't matter. My info says they're all the same '48 thru '54 and even the '55-'57 Hornets (except Jet and Italia, of course).

    Good luck.

    F

  • Ken U-TxKen U-Tx Senior Contributor
    Posts: 3,200
    If indeed the master-cylinder is as old as he states it may be, the rubber piston cup is probably swollen and with small tears/ cracks. The swelling causes it to cover the compensating port, blocking the return of fluid to the reservoir on release of the pedal. This causes the brakes to be applied all the time, thus the brake lights being on or flickering. The addition of the remote reservoir mounted on the firewall about 2-1/2 feet above the MC increases the pressure in the master-cylinder's reservoir to about 1PSI , due the column of fluid. This in turn resists the return of fluid to the master cylinder to a certain extent as well, but only is an issue if the compensating port is restricted also, as is the case when the rubber piston cup becomes swollen or distorted. The tears are why the inside of the rubber boot are wet with fluid. The new master cylinder will resolve the sticking brakes issue provided the pedal push rod is adjusted to allow about 1" free play when fully released. The old fluid must be THOROUGHLY flushed out. Brakes hoses, if they haven't already been replaced recently, should be replaced also, as the rubber inside can swell also and restrict fluid from returning to the master-cylinder. I recommend a high quality Low Moisture Activity type DOT 4 fluid. I do not use DOT 3 in my cars anymore. I do not like DOT 5 silicone due to the spongy pedal feel and some other issues.
         As to why the rubber swells, it is due to the old fluid breaking down and becoming saturated with moisture. Flushing the fluid once a year on an older car with the open vent MC caps is a good idea, esp if your car is not in a temp/ humidity controlled garage. Folks in Vegas, Phoenix might get away with flushing every 2 years or more, but if you are in Seattle, Baltimore, similar,  or anywhere in the UK, once a year is recommended.
  • RichardDRichardD Member
    edited March 23 Posts: 384
    Jason, if you are using the same remote reservoir as I showed you on mine {Wilwood}, you can use a 3/8" bolt shoulder (not threads) to slip in the tubing at the MC QUICKLY then tighten the clamps quickly to save most all of the fluid in the remote resv. WHEN YOU TAKE YOUR MC OFF.

    I just did it !!

    1953 Hornet 4Dr 

    A/C-PB-PS-Rearcam-12v-alumrad/elecfan-WWW-visor-etc

    https://goo.gl/photos/a2dCQaWVmu1KT1QFA


  • JasonNCJasonNC Expert Adviser
    Posts: 652
    Richard I took the Wilwood reservoir off because I couldn't get it to stop leaking.  The car came with a Toyota forklift fluid reservoir that I relocated from the fender to the firewall and it works great.  I'm going to flush out the DOT 3 fluid per Ken U's suggestion, so I'm not going to try to salvage the fluid in the reservoir.  Are you going to Sanford Saturday?  If I can get bugs worked out on the car that I bought from Lance, I may see you guys there.  Even if I can't get the '49 Super Six to cooperate, I'll probably drive the Kaiser as it running pretty decent right now.  
  • RichardDRichardD Member
    edited March 24 Posts: 384

    Remember that the wire-type clamp that they furnished with the kit would not stop it from leaking. I had to change to a SS wormgear type of clamp for the hose on the plastic reservoir.

     
    We have too much going on to go to Sanford--I hate it since I didn't make the Christmas party.  Give condolences. Thanks.


    My car is dead due to the brake problem now anyway. Put on Power Brakes but can't get the system to bleed out !! Took MC off this afternoon to redo it then go again.
     Guess I will have to look forward to getting to Lance's now.

    3/24>> just installed rebuild kit; found out that the 'rubber' check valve (#18) was torn all the way around, no way to check. I am NOT sure that was the problem- doesn't make sense to me, but sometimes nothing does !!!!



    1953 Hornet 4Dr 

    A/C-PB-PS-Rearcam-12v-alumrad/elecfan-WWW-visor-etc

    https://goo.gl/photos/a2dCQaWVmu1KT1QFA


Sign In or Register to comment.