Need your thoughts on '72 Satty brakes (long)

[cbunt1]

First the known:
'72 Satty, originally equipped with different brakes than it has now, assume 4w drums, manual brakes. Currently has front disc, with a proper manual disc MC. It has 10" rear, but don't know if that's really an indicator of original discs or not.

The current disc brakes are not original to a '72 Satty though...they're mounted to the rear of the hub rather than the front as would be factory on a '72, at least as I understand. Car was assembled in 2/72, so it's not a late-year '72 model.

I replaced the MC with a NEW (not rebuilt) MC, new rear shoes, drums, cylinders, rebuilt calipers, front hoses, and had to replace a banjo bolt in the process. I know I should duplicate swaps and changes side-to-side, but couldn't find but one aftermarket banjo bolt locally (have a set on order). I ended up going with the Dorman.

After bleeding the system out (bleeders on the top-side, which means the calipers are swapped right-to-left from "proper" part numbers) I went for a test drive.

I'm getting what is effectively a sticking caliper on one side of the car, (I really think they're both sticking, but one's just sticking harder than the other). After a drive around the block with a couple of hard braking tests, I pulled it in the driveway and jacked it up, and sure-enough, a wheel so tight I couldn't turn it.

I cracked the bleeder screw, and it squirted fluid as though someone was on the pedal -- and released the brake...so I feel pretty sure that I'm getting a hydraulic lock rather than a mechanical lock.

So...here's where I start dabbling in the unknown:
As I say, the calipers are mounted to the rear-side of the axle, which to my understanding is NOT OE for a '72 model. Additionally, every part number I'm able to look up shows a '72 using a straight-input brake hose rather than a banjo hose.

The calipers I bought match the calipers that were on the car, and I specced them from a '72 satellite -- they're a perfect match, except that the installation ends up being a left-to-right cross due to the location of the bleeders and hoses. I've verified that I don't have any hard kinks in the hose -- at least not that I can see.

My thinking is that the PO to the PO did a "junkyard upgrade" with '73-'76 parts. I haven't pulled the knuckle casting numbers, but given that the calipers mount to the rear, I'd bet that they swapped with the newer car both from an availability aspect and for the cheaper rotors and newer bearing configuration - I haven't pulled the hubs off the car yet to see. I'm basing this on the simple fact that the correct brake hoses I was able to find list for the 73-76 models. BUT....the calipers are '72 calipers.

So my first question is this: Has anyone had problems with banjo brake fittings not releasing pressure? I'm thinking of taking the new set and turning the neck (un-threaded) down a couple of thou to see if I can get more fluid clearance and possibly a release of the fluid.

Next question is: If the calipers on the car were designed for a straight-fitting, would that typically create a problem with fluid release?

Or is it likely that my problem is further upstream? In typing this, it occurs to me that drum brakes typically require residual pressure, where discs can't take it (given no return springs in a caliper configuration) -- were the valves on the '72 models setup to provide this pressure, or is this residual handled in the wheel cylinders like on the GM cars I've messed with in the past?

Any thoughts? It's got me a little baffled, especially since I think I'm working with a hodge-podge of parts...'72 calipers, '73-76 brackets, and maybe spindles, and unknown origin for the car itself.

I don't mind going back to the parts-house and getting '73 calipers to go with the rest of the setup, but I'd hate to do that and it turn out to be an issue with the banjo bolts themselves...

 

[moparmarks]

Could be the port valve not releasing the pressure. Check to see if it has a bypass pin. If it does then get the brakes to lock up and then pull the pin to see if they release.

 

[Satellite72]

It seems, at least in my experience on my 72, that those brake hoses are notorious for eventually collapsing and causing the issue that you seem to be having. I know that with mine, both driver and passenger side hoses did that on separate occasions (not letting the brake fluid return....almost like a check-valve) and I didn't realize it at first....before long I had some grooves in one of my rotors. I changed out the brake pads and brake hose and that cleared up the problem for me anyways. Oh, and my car is a January 1972 car with in-line brake hoses, not a banjo fitting.

 

[5.7 hemi]

Is the brake pedal rod adjusted correctly? Too much length on the rod and the mc will not come back, therefore pressure is still on the brakes, hence the fluid squirting out. This will also make the caliper not retract.

 

[cbunt1]

moparmarks -- I'm not seeing a bypass pin on the prop/metering valve. I'm also not sure whether the on one the car is stock, or correct for disc/drum confings. Seems like a good possibility, since in retrospect I've been having a drag on the fronts since before I started the brake overhaul -- just not as severe as it seems now.

Satellite72 -- I agree -- it's been my experience that a long looped brake hose can break down and become a check valve. These are brand new hoses, but of course, they still could be crap given the quality of aftermarket stuff. OTOH, I was holding pressure for a good 10 minutes when I dug into it last night (enough time to look around at it, scratch my head, and decide to put it on a jack and check it). The wheel was still pressurized enough that I couldn't turn it by hand until I released the pressure on the bleeder. And there was no obvious kink or collapsed hose just prior to cracking the bleeder.

5.7 hemi -- That's a good question. This car has a solid pushrod, and when I pulled the original MC, it was a direct-link to the MC rather than having a spacer-bushing like I've always seen on a manual MC. Rather than trust my instinct, I installed the bushing "as it should be" when I went back with a new MC...it seems odd that the brakes release in the driveway and drag on the road, but if it's marginal, the added heat and pressure of "real" driving just might push me over the edge. Perhaps I'll pull the MC and pull the spacer/bushing and see if that changes anything.

I'm sure the problem is simple, and it may very well be a "perfect storm" of marginal stuff (wouldn't be the first time for that in the deep internals on this car).

I think my next step will be to pull the master and pull that bushing and see if anything changes (it would at least effectively shorten the pushrod)...and then see what I can find out about the metering block that's in the car. Given that I've had weird steering behaviors (that I chalked up to REALLY bad bushings and ball joints) before I started this, I'm leaning toward upstream pressure a la metering block, and if it's worse because of an effectively too-long pushrod, it would all make sense.

Any quick-and-dirty ways to test the prop/metering valve and/or to determine whether it's the right one? I can't help but wonder if the metering valve is the original drum-brake model with a residual valve in it -- or were the residual pressures in these cars always handled in the cylinder end?

Lovin' this car, but let me tell you, sorting out aftermarket undocumented swaps and builds has been, um..."interesting" to say the least! :icon_study: At least I got good info from the PO on what THEY did--its the owner(s) before them that didn't leave any notes!

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Oh, and my car is a January 1972 car with in-line brake hoses, not a banjo fitting.

Thank you for that tidbit -- it helps me to confirm my suspicions about the calipers on the car (ours were mfg within a month of each other). Are yours mounted to the front or the rear of the hubs (forward or rearward?)

It could mean that I'm having a problem with the caliper not releasing pressure rather than pressure on the line -- its happening on both sides, as best I can tell, but worse on one side (the side with the aftermarket banjo bolt).

 

[Satellite72]

Cbunt1, to answer your question, my calipers are mounted toward the front.... so it does in fact sound like yours have been retro-fitted somewhere down the line. Good luck with it!

 

[moparmarks]

Can you post a pic of the port valve?

 

[cbunt1]

Can you post a pic of the port valve?

Sorry it took me so long to get back to this -- too many projects going on all at once. Here are a couple of pictures...let me know if they show you what you need to see.



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Sattelite72:

That's what I suspected. All told, I don't think it will make a HUGE difference, just as long as I can figure out exactly what I'm dealing with -- at least as far as the calipers go. I'm still waiting for some machine time at my buddy's shop to turn down some homemade banjo bolts to see if that's where I'm getting a hydraulic lock.

The good news is that at this point, it can only be one (or a combination) of three things -- the master cylinder pushrod clearance (i.e. the thickness of the bushing), a hydro-lock at the banjo bolt, or the prop valve. And as much as we're loving the rain here in Houston, I'd prefer it quit so that MAYBE I can color this brake system done, and get on to other things on the car

 

[moparmarks]

That is a drum brake valve. Needs to be changed to one for disc brakes.
The bypass pin is on the bottom of the valve. Has a rubber boot. Get the brakes to lock and then pull the pin. If they release then the valve is the problem.

 

[67 coronet]

easy to check the master pushrod clearance.lockem up and then unbolt the master and see if they release.i am with moparmarks,that looks like a drum diverter valve,not a prop valve.

 

[cbunt1]

That is a drum brake valve. Needs to be changed to one for disc brakes.
The bypass pin is on the bottom of the valve. Has a rubber boot. Get the brakes to lock and then pull the pin. If they release then the valve is the problem.

That would make perfect sense what with it holding pressure and such. It also explains why the car feels like the front discs aren't carrying enough load.

So here's the next question...what would have been properly installed in that era's disc/drum setup?

Obviously I could just put an aftermarket adjustable proportioning valve in there, but I wonder if I wouldn't be better off with a proper metering/combination valve instead.

I have what I would consider a little more than a basic knowledge of the hydraulic side of braking systems, but not MUCH more...

I've read a number of articles on the differences in valving -- as I understand what I want in a balanced road system is metering rather than strict proportioning -- e.g. the rears just begin to engage (take up the slack, really), then the fronts, with the fronts carrying more braking load -- thus reducing the likelihood of a rear-lockup situation on the street.

Is my thinking correct, or am I over thinking this, and should just grab a good adjustable proportioning valve, set it up, dial it in and forget it?

For what it's worth, this isn't truly a daily driver, but my goal is to use it for most of my running about town (seeing as I work from home, and don't really have a "commute" per se).

Thanks to all of you for your help and guidance!

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easy to check the master pushrod clearance.lockem up and then unbolt the master and see if they release.i am with moparmarks,that looks like a drum diverter valve,not a prop valve.

Excellent point. Given that I was having some problems that (looking back) seem like the front brakes dragging before I replaced the master and calipers, I'm thinking a valving problem seems likely -- and I wonder if the bushing hadn't been removed by the PPO (or before them even) trying to chase exactly that. Either way, once I eliminate the valve question, if they're still dragging, I'll look toward the master...and unbolting it locked sure seems like a quick check.

 

[moparmarks]

71B/E disc used a 2-piece brass setup. 72-4B/E disc used a cast iron valve. Not too hard to find. I can check and see if I have any right now, probably do.
Or could just use an adjustable valve on the rears.

 

[cbunt1]

If the function on the original system is purely proportioning, then I might as well go ahead and put in an adjustable valve and be done with it . . . the 'tinker' in me is usually all for anything I can adjust as long as I'm not giving up some unforeseen functionality.

And really, it shouldn't be anything I can't setup with a tubing bender, given that I've got at least an extra coil or so in both the front and rear lines . . .

Swap like this what -- two or three hours, or I could get a couple of friends over, buy a case of beer and stretch it out all weekend! :iamwithstupid:

Thanks for the heads-up on the drum valve. The possibility had occurred to me, but I dismissed it as unlikely.

 

[cbunt1]

Well, on second thought, and further examination, it looks like just throwing a prop valve in the mix doesn't solve the problem of the front-end holding pressure. If you have one of the original valves on hand, I'd buy it off of you -- otherwise it looks like my best bet is either the MTM semi-repop unit, or the one from inline tube -- otherwise it looks like I'd be engineering from scratch with hold-off/metering, and a rear prop valve (not sure where the brake light switch would get setup...not that I can't feel a pedal go to the floor all by myself, and IME the brake light switch only serves to confirm my fears that the brakes just failed!)

Or maybe you know something I don't know as far as a part number My google-fu isn't so good tonight, must be the long day at work! LOL

 

[67 coronet]

http://www.getdiscbrakes.com/catalogsearch/result/?q=pv12take a look here,they have alot of listings by year and might make it easyer.

 

[moparmarks]

Do have a 72B/E valve

 

[cbunt1]

I think this will solve the problem. I'll update the thread once I get it installed and tested!

Thanks everyone for your input, and thanks, MoparMarks for digging around and finding me a part!

 

[cbunt1]

OK it's time for an update. I'm nowhere near finished, but it's looking good.

I swear I'm going to get a pair of fuzzy DOMINOES to hang from the mirror of this car instead of dice like most people! LOL

Completing the partial upgrade done by previous-previous owner has turned into a complete brake system overhaul. When I started this thread I had just put new calipers, brake hoses, wheel cylinders, pads, shoes, and drums on the car. The Proportioning valve I got from MoparMarks is exactly what I need to complete the job, at least from a hydraulic distribution and valving point of view.

BUT, in installing it, i discovered that the fittings were still setup entirely for the old 4-wheel drum system with 1/4" fittings on the front and rears, instead of the 3/8" for the front and 1/2" for the rear I needed. No worries--just grab adapters. EXCEPT the old fittings were corroded into the distribution block to the point that the nuts rounded off--even using line wrenches.

Still not a real problem -- just trim 'em off, put the right fittings on, and flare -em up. Sounded great until I remembered that the fittings at the wheel-ends on the front were seized...so I decided to just replace the brake lines all the way around.

In so doing, I think I discovered another portion of my lock-up problem. The front brake lines were armored 3/16" lines, and were original to the car as best I can tell. This means that when they did the drum-to-disc swap they just bent-up brake lines to meet up with the new brake hose mounting locations. I found some partial restrictions (read small kinks) in the lines when I took everything out of the car that I couldn't see (and wouldn't have been able to spot, since they were near the frame-holes). I suspect this is an additional source of my pressure problems.

SOOO...I just finished fabbing new brake lines, and will install them into the car over the next couple of days -- hooking them to the "new" prop valve, and VOILA! I should have working brakes.

At least when I'm done with this, I'll know that any problems I have are due to mismatch and not faulty parts/lines/brake hardware!

I bought this car to "do it my way" (as opposed to the Skylark that SWMBO likes to keep more-or-less stock) ... I guess I should be careful what I ask for....this just might be the car that I go to change a radiator cap on and end up overhauling the entire engine!

 

[cbunt1]

Well, final update. No great big stories this time (I promise.) Finished installing the brake new brake lines. At this point, there's nothing original on the car in the brake system other than the backing plates on the rear drums!

BUT...I've had it out a few times, and everything works perfectly. I can get a good solid "sliding" stop out of the car, it skids straight, and all the brakes are carrying their loads. The kinked-up brake lines, in combination with the wrong valving seems to have been the culprit.

Thanks everyone for your help and wisdom...this was really beginning to irritate me!