Dry brake master cylinder

bachman502

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My deuce hasn't been on the road in a few years do to torque rod bushings and finances. A few months ago I put some batteries in it to just to start it and drive around yard. I had no brakes. Checked master cylinder and it was dry. I added the correct brake fluid type to master cylinder and over filled it. Obviously master cylinder is now covered with fluid. I looked at all the tires looking for brake fluid and seen none. Check for obvious leaks around brake lines and didn't see anything. This past weekend I drove it around yard and I just barely can feel brakes engaging. Looking for some advice and opinions on where to start. I did replace the wheel cylinders up front years ago. Should I start with a brand new master cylinder for piece of mind and then work my way towards wheel cylinders? What about air pack? I hate to go through the system and just to find out master cylinder is bad. At same time hate to replace that if not needed. Anybody replace master cylinder just because for safety reasons?? Thanks for advice. Just not sure where to start.
 

Valence

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After filling the master cylinder, did you bleed the brakes? You first need to bleed the air pack, then move to the axles. I start with the wheel cylinders (following the brake lines routing) farthest from the master cylinder:
Passenger middle axle >> Passenger rear axle >> Driver rear axle >> Driver middle axle >> Driver front >> Passenger front

But if you can't find any leaks, it could be a failed air pack. It will stuck brake fluid into it's big air chamber. Another indicator that the air pack has failed is if brake fluid is being sprayed out of the vent line (under the hood, to the right side of the air cleaner - it's where the air is vented after you release the brake pedal).


As per your question if anyone replaced their master cylinder just because safety reasons... I did. It was about $65.00 for an NOS one on eBay, but I also did it at the same time I was attempting to rebuild my air pack since I was already in there, having problems, and I didn't want to have another problem anytime soon.
 
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Valence

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I also highly recommend installing a "remote brake fluid reservoir". It makes checking and topping off the brake fluid level SO MUCH EASIER and faster. :)
 

bachman502

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No I did not bleed brakes after I added fluid. It wasn't a priority at the time. I wanted to see if the fluid would disappear after I filled it. Unfortunately I overfilled it. I wasn't sure about the air pack and how to tell if it's bad. I don't mind replacing master cylinder for peace of mind. I do have another surplus air pack that I purchased for a spare years ago. Didn't want to swap that unless I had to. Also didn't want to throw money at a problem just by guess what part was bad. Should I rebuild air pack just because? Or check for fluid in air pack? I will do the remote reservoir also. Just want truck SAFE
 

Valence

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I'm not very good at recommendations, because I personally tend to do more than is necessary and additional "while I'm in there.." tasks. But, if you'd like to hear it, my recommendations, in order, for these single circuit brake systems where a single point of failure means no brakes:

  1. Install remote reservoir (~$45)
  2. Rebuild all 6 wheel cylinders. Replace if any are too rusty to hone out (~$75-~$200)
    1. This usually leads to repacking wheel bearings and replacing oil seals
  3. Inspect all brake pads and shoe return springs and replace as necessary ($?)
  4. Properly adjust all brake pads ($0)
  5. Rebuild or replace air pack and master cylinder (~$120 -$500)
    1. If necessary, upgrade brake light switch on air pack to the air-operated kind vs the hydraulic operated.
  6. Inspect/replace brake pedal return spring (~$5)
  7. Replace the 5 flexible brake lines (~$100-$280 depending on quality)
    1. This usually leads to inspecting the hard lines or replacing in part if the flexible lines are rusted in place or the hard line flange nut has been mistreated in the past...

I tried to rebuild my air pack ($80) and it failed - or the job I did failed as it really sucked brake fluid. So I just opted for the new replacement ("short" style air pack from Erik's for $400...)


You most certainly can do just one piece at a time, but a dry master cylinder doesn't necessarily indicate a bad master cylinder or air pack. You said you already rebuilt the front wheel cylinders. How "bad" were they? Maybe you should do the rear's then if that doesn't solve the problem move to the air pack and/or master cylinder?
 
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Wildchild467

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My Street Rod uses DOT 5 as well as the Deuce. Every couple years I need to top off the brake fluid on my street rod. I have never seen any leaks but it just seems to use some ever so slightly. Now, I have looked over the brake lines and there are never any leaks or even any remote wetness around any connections. My dad's studebaker is the same way with DOT 5 fluid. It just seems to use some ever so slightly over the years. I check my fluid once or twice a year and top it off if its down. Always make sure it is full because less air in there also means less moisture. Not sure where the brake fluid goes, but I have never, ever felt like my brakes would not work or that anything was unsafe. DOT 5 is just funny like that... it needs to be checked once or twice a year. Someday, I would like to get a remote reservoir to make things easier.
 

rustystud

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My Street Rod uses DOT 5 as well as the Deuce. Every couple years I need to top off the brake fluid on my street rod. I have never seen any leaks but it just seems to use some ever so slightly. Now, I have looked over the brake lines and there are never any leaks or even any remote wetness around any connections. My dad's studebaker is the same way with DOT 5 fluid. It just seems to use some ever so slightly over the years. I check my fluid once or twice a year and top it off if its down. Always make sure it is full because less air in there also means less moisture. Not sure where the brake fluid goes, but I have never, ever felt like my brakes would not work or that anything was unsafe. DOT 5 is just funny like that... it needs to be checked once or twice a year. Someday, I would like to get a remote reservoir to make things easier.
I have also found that the DOT 5 brake fluid seems to want to "migrate" out of the master cylinder over time. I have also never found a leak but the fluid level does go down ever so slightly.
 

gimpyrobb

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Sounds like its been a while since you were in your brake system. As long as you KNOW FOR SURE the wheel cyls are good, I'd just pull the master cyl and go through it. I see no reason to replace it with new if its not rotten. Pull apart the current master cyl and look at the seals and bore. Maybe order a rebuild kit to have on hand. After that, I'd just put it back in and bleed the system, should be fine.

If there is any question about the wheel cyls, I'd rebuild them too, its like $15 per kit.
 

jimk

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My m35a2 was like that when I got (~10y ago). Dry master w/no leaks. I added fluid and a decent pedal came right back. Since then I have bleed it and done the major adj. Brakes function has always been really nice.

Re shoe'd the 5t a few years ago (6?). Master was dry this spring, pedal was fine. No leaks. Added fluid. Pedal rock solid but was a bit low so did the minor. Brakes excellent. Checked the deuce at that time (been maybe 5? years). Fluid was very low. I told myself I'd get in the habit of checking brake fluids at the beginning of every year. I'll know if I'm a listener next year. Right now I'm doubtful.

If the rubber lines are crack free and you can leave a carpet of skid marks your brakes are safe. It shouldn't take a lot of pedal pressure. If the pedal is hard you don't need to bleed. If pedal is high (and they don't drag) you don't need to adj. Where the fluid goes is a mystery. I don't worry about it.

Uh, my old Fiat 850 coupe has/had DOT5. That one was sitting untouched for over 15y a few years ago. Decided I best start it so put a bat and gas in it. Everything worked but the brakes and the w-washer. Master was dry. I add Dot 3 (forgot what was in there) and the pedal came right back. Now I need to replace fluid. Been saying that for a few years now.
 

rustystud

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This brake fluid issue has something to do with use too. My daily drivers all have DOT 5 and the fluid level stays where it is suppose to. My deuce which doesn't get driven much anymore has the disappearing fluid trick. Really strange !
 

Aussie Bloke

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G'day everyone,....


Funny thing is I have my Dot 5 go AWAL.

I keep filling up the remote reservoir but cannot find out where the fluid is going,....?


I can run the Deuce all day and not a drop will go missing yet if it sits for a week next time I cheak the fluid level it will have fallen, it seems the longer my Deuce sits the more the level drops.



(1 baffled Aussie.)




Aussie.
 

bachman502

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I cleaned up the externals of the master cylinder and air pack yesterday with brake cleaner. Removed the air pack skid plate. Scraped the mud off. Added brake fluid and bled the air pack. I will work on bleeding each axle next. I will keep an eye on the master cylinder area since it's clean. Its probably our wheel cylinders that allow the slight sippage.
 

RodUSMC1962

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The remote unit is the greatest thing going! Just a peek behind the seat and you know if you have a problem, no messing around in the dirt under the floor, only takes a small amount of time to install. :beer:
 
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