Roger from AAJ is hard to get a hold of, last time I spoke with him he wasn't in the best health. MPB has been helping and gave me some advice. And a lot f it goes back to the push rod, which I will check again.
All 4 locked up/grabbed, so my plan of attach will be two fold, first, rebleed the lines, make sure the fluid isn't to the top. Drive around and see what happens. If it doesn't lock up again, problem solved. If it does, I will loosen the bolts on the MC to the firewall and see if the MC sliding forward releases the brakes. If it does, we know the push rod is too long.
Sometimes I wonder why anyone would ask a technical/mechanical question, such as “why am I having this ______ problem”, on this forum. The answers vary so widely, sometimes from one extreme to another, how do you know which one is correct or best? Maybe a lot of input gives you ideas you hadn’t considered and from those options you can decide what to do. I guess “it takes a village”....
Well exactly what you just said. Sometimes you need a different perspective. I honestly thought this was a brake fluid overfill issue but a lot of folks are leaning towards the pushrod. I think my original issue was trying to understand how the problem got worse when I drove the car more. But a few people answered that and it clarifies how it can happen. More input isn't a bad thing in my opinion.
You’ve done what you’ve done. As I remember the E brake on a 58 Dodge is on the trans for those who at thinking it could be the problem. I don’t know your thinking on rear disc brakes. When I was converting my 56 each company I talk to told me to keep drums on the back. I wanted to up grade the rear end and did just that. When I bought an “engineered” disc brake for the front each company asked what was in the rear and the pedal ratio. Many have installed disc/disc and are happy and others have continued problems. You show a MC that’s GM disc/disc and here it’s said it’s disc/drum and a Mopar. You also say it’s been rebuilt to be disc/disc... why would anyone do that with disc/disc being so prevalent today. I don’t know who AAJ is but if the owner/tech cannot be reached. I’d be taking everything off and start over. You started be saying you did not like your tapered drums and you don’t have them. What rear end did you install. What diameter discs. These are a lot of questions but I think you need to tell us a little more. I know it doesn’t matter but my kit was from Wilwood.
Theres really not much of a difference. The biggest thing is that a master cylinder designated as for “drums” usually just has an integral “residual pressure valve” pressed into the port right where the line goes in. Simply popping that thing out of there so you need to do to operate disc brakes. Well I’m guessing is that your master cylinder is supposed to have the thing removed. Rendering it suitable for disc brakes. The terminology “built” for disc brakes Doesn’t really make sense. And if by some chance somebody forgot to pop it out of there it’s still for drum brakes not yet suitable for disc brakes. All, every single one of them,,, wheel cylinders need a device to keep air out. Most of our hamb era stuff utilizes a RPV to keep positive pressure against the cups. Some later model wheel cylinders have an extra spring in the cups.
The MC I showed is the Mopar MC rebuilt by MPB for disc/disc applications. MPB and I went over a lot of details regarding pedal ratio, bore size, etc. And MPB has been there to help troubleshoot. The point of the thread was for clarity and a second opinion. I don't like the tapered axle set up because of how the drums and hubs were swedged together. I kept the tapered axles, removed the drums and installed disc in place of the drums. Now I don't need a special puller to remove the brakes. Disc are 11" as per AAJ.
So do you know for sure that the valve was removed or just assuming? Sent from my SM-G950W using The H.A.M.B. mobile app
Residual pressure is a very small pressure. Not nearly enough to lock up the brakes. Just enough to make them drag slightly, at most. Sent from my Trimline
Since everything is pointed at the pushrod,,, How did you verify the free play? (having all 4 lock up is a real good landmark for that) And before the Changes, where your oval rear brakes even working at all?
Well I measured with my caliper ( the tool not the brake) and got roughly the same depth between the old MC and new MC. The old MC has a depth 18.57mm and the new C has a depth of 18.51mm, I figured .06mm would have very little effect on the MC. For the original rears, one worked, for the most part, the other had a rusted out wheel cylinder and leaked. Both needed new drums, which for that car isn't a cheap undertaking. I think I was quoted $500 for each drum.
Every time you stopped you added a little more pressure. when you opened the bleeder and got rid of the pressure you started over.
@sunbeam, do you have a guess on the cause of the pressure build up? I had a similar issue with four wheel drum breaks. A change of master cylinder resolved the issue. I never took the old master apart to see if I could find the cause. Phil
You also need to consider if the "radius" at the end of the pushrod matches the one in the master cylinder. Assume that your previous MC had a larger radius pocket for the pushrod to fit into than the new MC. The resulting mismatch results in the pushrod not seating into the MC piston pocket as deeply, so may be holding the MC piston forward of the relief hole. The difference is likely minimal, but it doesn't take much of a change in piston position to cover those holes.
I was thinking about that as well, not something I measured so it's very possible to be part of the problem.
Sooooooo, isn’t a leaking cylinder kind of like an open bleeder and brakes aren’t ever working working for real working? Here’s my $0.02 You’re original set up pedal and pushrod was equally wrong but didn’t show itself and now it does. Maybe I’m wrong but I’ll bet I’m not
The amount of fluid in the master makes no difference. Some guys fill them to the top, I like 3/16" below the top. But siphon off a little, can't hurt. Loosening the master may release the brakes, worth a try and easy to do.
Not too easily. I tried but the leverage and return spring make it difficult to get a good feel for it. But I will try again this week.
When the front brakes were swapped over last year I installed a new MC for disc/drum. The push rod was adjusted at that time because on the first test drive the rears grabbed. At that time the rear drums were inspected and did not leak but the rubber flex hose from the hard line to the rear was replaced because it collapsed. So is it possible, yes, but the brakes weren't leaking then. But I'm not ruling anything out.
So rear are/were leaking because it’s rusted but not leaking? This is really too hard to follow anymore. This damn brake fluid is really smart
Last year when I installed the front disc I checked the rear drums. They were not leaking at that time but there was visible rust. This past weekend when I started pulling the rears off I found that the passenger side wheel cylinder was leaking.
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