dan01wilson Posted November 11, 2015 Report Posted November 11, 2015 After running errands today in my 1951 Dodge B3B Pickup, brakes were dragging/locked to the point we barely got home. I noticed the brake light was burning continuously, which means there is residual pressure in the system. All I did was disconnect one of the wires from the brake light sender to keep from running the battery down. Thinking back, it seems like the brake pedal has progressively engaged higher and higher. This problem is obviously related to the master cylinder. Is it a simple adjustment issue? Where should I start in the morning in diagnosing this issue? Thanks in advance for your expert advice. Quote
Jerry Roberts Posted November 11, 2015 Report Posted November 11, 2015 If that doesn't work , you might have one of the three rubber lines collapsed on the inside preventing flow back to the master cylinder . Quote
dan01wilson Posted November 11, 2015 Author Report Posted November 11, 2015 "Rubber lines collapsed on the inside" On the inside of the master cylinder? Quote
Plymouthy Adams Posted November 11, 2015 Report Posted November 11, 2015 no the flex line is what he is referring to...the one that feeds the rear brakes at the rear axle "t" and the one on each of the front wheels...these are the rubber flex lines in the system.. 1 Quote
dan01wilson Posted November 11, 2015 Author Report Posted November 11, 2015 flex lines are a real possibility. last replaced them approx. 1980 Quote
Young Ed Posted November 11, 2015 Report Posted November 11, 2015 flex lines are a real possibility. last replaced them approx. 1980 If you haven't messed with the MC adjustment start with those flex lines Quote
Plymouthy Adams Posted November 11, 2015 Report Posted November 11, 2015 Ed makes a good point on the master cylinder...even if you have not messed with it..do check the bleed hole for being clear and also that the master cylinder piston is full returning against the stop and THAT there is nothing like rust or corrosion that would prevent this plunger from fully retracting.. Quote
Dodgeb4ya Posted November 11, 2015 Report Posted November 11, 2015 The M/cyl piston might not be returning back to the stop so as mentioned check the bleed back hole to be sure it is clear after several pedal pumps. Quote
dan01wilson Posted November 11, 2015 Author Report Posted November 11, 2015 How do I "check" the flex lines? Is it advisable to just replace them since the existing ones are 35 years old? Also, how do I check the bleed back hole in the MC? Take off the MC lid and probe with fine wire? Thanks for the responses. Quote
Don Coatney Posted November 11, 2015 Report Posted November 11, 2015 This might or might not help. Quote
Plymouthy Adams Posted November 11, 2015 Report Posted November 11, 2015 you check by seeing if the brakes pull off when relased..the problem is that the master can generate up to 1200 PSI and that will allow fluid to be easily pushed to activate..the problem is the return, only the small springs is the driving force to return the fluid to the master...on disc..is is just the slight roll of the rubber square o-ring doing this job.. ensure your master is not suspect by clearing the relief port..and ensuring full return of the piston...and that you have the proper free play pedal to master...apply brakes..if they do not release when you release the pedal..crack the bleed valve..if the brakes now release...you have one of two problems..collapsed hose or you have some serious crud in the wheel cylinder Quote
Jeff Balazs Posted November 11, 2015 Report Posted November 11, 2015 FWIW. I would start by checking the pedal linkage and floorboards to see if any of this is preventing the rod to the M/C from fully retracting. The adjustment of the linkage allowing for free play can be a bit fiddly on these trucks. The cab may have settled some or shifted enough to have an effect on this. Jeff Quote
dan01wilson Posted November 11, 2015 Author Report Posted November 11, 2015 Drove truck around the block this am. Pressure in system is decreased to where it drives ok. Jacked up front end and removed LF wheel/tire. Both front brakes are dragging a little. Does this point to the MC, or would one partially collapsed flex line affect the whole system rather than just the wheel or axle it serves? Thanks Quote
Don Coatney Posted November 11, 2015 Report Posted November 11, 2015 If when you pump the brake pedal several times and the pressure increases with each pump I don't believe the problem is collapsed lines. I believe either your pedal is not returning all the way due to rod length adjustment or the return port in the master cylinder is blocked. Quote
dan01wilson Posted November 11, 2015 Author Report Posted November 11, 2015 This is the type MC my truck has Quote
MBF Posted November 11, 2015 Report Posted November 11, 2015 (edited) You can narrow down the source of your problem by pumping up the brakes so that they hang and then: 1. cracking open the fitting on the master cylinder and see if the pressure releases. If it does, the problem is likely master cylinder related. 2; If it passes that test (no pressure released), pump them up again and open the bleeder on the suspected front or either rear cylinder. If the brakes release and you get have pressurized fluid at the bleeder screw it's the lines. 3. If you don't get any pressure release when you open the bleeder(s) you've likely got a wheel cylinder(s) hanging. I think I have that right. That's what I did to verify that my rear flex line was the culprit since all of my wheel cyls were newl within the past couple of years. Mike Edited November 12, 2015 by MBFowler 1 Quote
Jerry Roberts Posted November 11, 2015 Report Posted November 11, 2015 How do I "check" the flex lines? Is it advisable to just replace them since the existing ones are 35 years old? Also, how do I check the bleed back hole in the MC? Take off the MC lid and probe with fine wire? Thanks for the responses. Do a search of the forum on master cylinders . What you are looking for is a photo that shows two holes on the inside bottom of the master cylinder . And yes you would need a very fine wire or probe to clear the smallest hole . That is a good place to start . others have had the problem with brakes locking up and found the solution there . Quote
Plymouthy Adams Posted November 11, 2015 Report Posted November 11, 2015 Jerry Roberts, on 11 Nov 2015 - 5:14 PM, said: Do a search of the forum on master cylinders . What you are looking for is a photo that shows two holes on the inside bottom of the master cylinder . And yes you would need a very fine wire or probe to clear the smallest hole . That is a good place to start . others have had the problem with brakes locking up and found the solution there . picture has already been posted.... Quote
HanksB3B Posted November 12, 2015 Report Posted November 12, 2015 (edited) This is the type MC my truck has To make it easier to fill, you can rotate the cover plate 180 deg. I know it's better I aleady did that. The cost of re-doing your entire brake system all new lines slaves and a master cylinder can be done for under $400. It sounds like a lot, but afterall it is your brakes. Good Luck with your truck, Hank Edited November 12, 2015 by HanksB3B Quote
dan01wilson Posted November 20, 2015 Author Report Posted November 20, 2015 Received my new Raybestos flex lines today. Hope to be able to fix my truck this weekend. Checked my linkage and the free play seems to be ok. I have not been able to see or probe the return hole in the MC. Last time I went through these brakes was 2009, and I came up with a good one-man bleeding scheme. I used a bug sprayer with the required fittings, put Dot 3 in the bug sprayer, screwed into the MC filler hole threads, kept 6-8 psi or so pumped up and bled each wheel cylinder. Worked much better than my Mity-Mite vacuum setup. Since my MC is lower than my wheel cylinders, gravity bleeding is not an option. I will try to remember to make some pictures of my bug sprayer bleeder arrangement and post them. All the common sense and sanity checks I have gotten on this forum are invaluable. Thanks again Quote
HanksB3B Posted November 20, 2015 Report Posted November 20, 2015 (edited) I don't know if I like rebuilding carburetors or brakes better... hard choice...they are both a lot of fun. But one thing that can mess you up is doing them in a hurry because your vehicle is not driveable and you are in a hurry. If you can, first time around it's best to buy all new brake components NEVER SURRENDER YOUR CORES pay the core charge and buy the rebuild kits. Then you have relined shoes, master and wheel cylinders waiting till you need them. Have fun ! (and cool on the bug sprayer) Hank Edited November 20, 2015 by HanksB3B Quote
dan01wilson Posted November 24, 2015 Author Report Posted November 24, 2015 Here is my bug spray bleeder. Only issue is sealing it at the Master Cylinder, since those are straight threads. I finally used a washer AND tape on the threads and got it sealed. The bleeding itself only took 20 minutes or so. Quote
HanksB3B Posted November 24, 2015 Report Posted November 24, 2015 Bug Spray Bleeder.jpg Here is my bug spray bleeder. Only issue is sealing it at the Master Cylinder, since those are straight threads. I finally used a washer AND tape on the threads and got it sealed. The bleeding itself only took 20 minutes or so. Yours is better, there won't be any chance ants and roaches getting into your engine. Hank Quote
dan01wilson Posted December 4, 2015 Author Report Posted December 4, 2015 Drove my B3B approximately 25 miles today running errands and the brake issue is solved. I believe the root cause was brake pedal free play adjustment. Slightly puzzling since no adjustments had been made. On person who provided input on this thread said the cab can shift or settle enough to change these type adjustments, so maybe that's what happened. At any rate, truck is fixed and all ready for Christmas parades. I don't mind that I replaced all flex lines; after 35 years, it was time any way. Thanks again for your help. 1 Quote
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