Remember the thread I posted about the problems I had with my front brakes locking up after driving on my T roadster? Well the good information offered to me by the likes of squirrel, Bruce Lancaster and Tommy, helped out a bunch. I found that the plunger from my pedal to the piston in my m/c had no play. Readjusted it to include about 1/16" play and the brakes don't lock up near as I can tell without driving it. Now the next challenge comes in. Early in this mis-adventure, I thought my front residual pressure valve (10lbs) might be causing the lockup problem, so I took it out. Now, after adjusting the plunger and bleeding the brakes four times (yes, you read right, 4 times), I can not get sufficient pedal pressure until I've pumped the brakes three times. This is unacceptable. I have new '41-8 wheel cylinders on all four corners, powered by a new '80's Jeep master cylinder with a bore size of approximatley 1 1/8". Question #1: Am I just not bleeding the brakes correctly, or is there something else wrong at play here? Question #2: Do I need to re-install my residual pressure valve in my front line to correct this problem? Thanks, r
start with the basics. Adjust the shoes up. If I remember right it is 4 wheel drums. Adjustment can be critical. It may not be air in the lines. Often you have to pump the pedal to get all of the slop out of the adjustment. Taking that slop out with an adjustment may bring your pedal back to the top. Are you getting anything out of the wheel bleeder screws?
Tried that last night and it really didn't help the situation. I was thinking along the same lines as you. r
IS the master under the floor? If so, your brakes could be draining back into the master requiring you to pump them up everytime you use em. How are you adjusting the drums? If you just adjust em out until they start to drag, you're prolly not getting them adjusted right. You need to run em out until they're tight, this makes sure they're centered, and then back em off. I was in brake hell for a few months before I learned the ins and outs of 4-wheel drums (thanks, Steve). Eventually, I used a master from a '68 Olds with 4-wheel drums ($30 delivered from rockauto.com) and it was sized and valved just right for our '58 Olds from the getgo, no need for any residuals. Good luck. Also, I'm curious if anyone knows the answert to this - if you run an underfloor master (normally requires a 2lb residual to prevent drainback) and 4 wheel drums (requires 10lb residual to overcome spring tension in drums), do you run a 2lb and a 10lb, or will the 10lb do the trick?
Yes, the m/c is under the floor. I will adjust the drums the way you suggested, but I know that alone will not solve the problem. Thanks, r
I had a heck of a time getting my brakes to pump up when I first plumbed them last summer. It ended up that I had a bad flare on one of the tubes I got from napa. It didn't leak fluid, but would let just enough air in to keep me from holding pressure. I was pulling my hair out- ask Kevin and Kerry LOL. I ended up just buying a new line and viola.
I've never run one under the floor, so take my advice for what it's worth, but from all the reading I've been doing in the course of redesigning the brakes on our '58 O;ds, it would be surprising if you could get a pedal at all with a master designed for discs (i.e. NO residual valves at all) run below the floor to drum brakes with no residual valves. Also, adjustment alone could fix the issue as being out of adjustment shows itself with a low pedal or no pedal that goes away when you take up the slack by pumping up the brakes. I'd still bet the issue is the lack of residual valves though. Remember, most modern cars run a separate combo valve that has a section dedicated to acting as a residual valve for your rear drums. The reason is that the springs in your drums push back on the wheel cylinder when you release the brakes and forces fluid back into the master. Good luck, brakes seem to be the most frustrating part of any project for me as the best you can hope for is that your car stops. It's not like working on the motor, which makes it run better or the body, which makes it look better...
If it works fine, why'd he remove it? I thought he suspected it was bad. If so, i suggest he put something back in it with the master under the floor. Whether it be the one he took out(not if he thinks it's bad) or another one
He thought it was the issue, then later discovered it was actually the pedal not backing all the way off when he released it. I'd normally make some real smartass comment here about you reading the whole thread before posting, but your cars always leave me in awe, so I won't...
"you mean i dodged a bullet?" Ha, ha. Groucho dodged a bullet... Here's my plan. Take out the m/c and bench bleed it. Re-install the residual pressure valve in the line for the front brakes. Bleed the brakes. Then check to see if that fixes the problem. If not, then I know of a brakes shop close by that I trust. They will get the job of correcting the problem to keep me from burning the car to the ground or going after it with the 5lbs. sledge I have close by... Can you tell I'm really tired? r
So, i DID read it right? The residual's NOT in the system at this time? That's what i thought i read. PS-put the damn M/C on the firewall where it belongs. Hahaha
Bullet? I doubt it, us Ohioans aren't very bright. Raven - Keep your head up, man, like I said, it's completely frustrating and not very rewarding until it finally works right, but being able to stop is worth it and, once it's right, it's right. You never put adjusting your wheel cylinders in there. It should be right before ripping the whole thing apart again...
so i run a master under the floor of my pickup, 4 wheel drum brakes and it works just fine, i run a 1970 chevy pickup master for 4 wheel drum brakes and as far as i know its only a 2lb residual valve but how can that be checked?, if brake fluid is returning back to a master that is below the level of the wheel cylinders wouldnt that show up as a rise in brake fluid in the master, i guess air would have to enter the system by sliping past the rubbers in the wheel cylinders to allow the fluid to leave the wheel cylinders and end up back in the master?, when i find that if i pump my brakes twice and the peddel comes up some, i adjust my brakes and then i cant pump them up anymore, the way i have always adjusted my brakes is adjust them till they drag a little, get in the seat and pump them a few times, get back out and they usely have no drag then and i adjust them till i have drag again, this goes on till the amount of drag doesnt change after pumping the brakes, then i slack my brakres off just till theres no drag, i know its best to have a little drag but wearing out my brakes and burning more gas to over come that drag is a drag. can anyone show a cross section of a master and explain what the spring inside masters are there for?
Here's what I'd do, in order: -install 10 lb residuals in front and back lines -adjust pedal plunger = DONE -adjust brake shoes till they just skiff by -bleed all brakes again, on the car, not on the bench -check for leaks inside the brakes and out -TEST DRIVE -recheck for leaks -readjust/finetune shoe adjustment FYI - they say the bottom pins on '40 style brakes should be done before the side cams, but I always have better luck sneeking up on both at the same time.
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