Rifleshooter
Well-Known Member
The only thing I can think of is maybe the proportioning valve needs to be adjusted. The brakes have always been bad even from before I started replacing parts on it.
Brake Proportioning
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AJ/FormS
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See I told you I make mistakes.lol, I coulda sworn I read new booster, I even went back to double check once.
Ok no matter, then just ignore the start up procedure, the rest is the same, namely the pedal must BE hard, REMAIN hard AND not sink with a given pedal pressure. If it sinks, the M/C has in internal problem.
Without the booster, it takes a good deal more leg power to affect a given stop, than it would with a booster. This means if the rear W/Cs are too big, they will skid sooner. And that takes us back to Q5, which is ,as yet, unanswered.
Further more Q10 and Q11 are also not yet answered. If the rear cables are not fully parked, perhaps due to being seized, then the park-strut will be partially energized, And so as soon as you step on the brake, BAM!, the rear shoes start to drag, and the secondary shoe is already waaaay out there ready to go to work. When this happens hydraulic pressure inside the M/C, stops or prevents the application of the front brakes. The system is designed to have the pistons in the rear wheel cylinders to go out a certain distance before applying the clamp. During this travel-time the pistons in the M/C are taking up hydraulic slack in there, and then with db's BAM!!the calipers put the bite on the rotors, About the same time, the rear slack is taken up and then BAM, the rears start working. You can prove this by clamping the rear flex-hose. Don't do this, BTW, it's real hard on the hose.
Like I said; please answer the questions.
I know you kindof want to change the C-valve, but know this; It is the absolute least likely part of the system to make trouble. In 48 or so years of mechanical work, I have yet to see a failure.They are an incredibly robust and trouble-free,simple, device.And it is not adjustable.
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Rifleshooter
Well-Known Member
Q5: there was only one option for the W/C so there's no chance of that bring the wrong size.
Q10: the brake light on the dash only ever comes on when the parking brake is applied.
Q11: the parking brake pedal does return all the way. But I'm starting to think I have the star wheels on the rear drums adjusted too far out. Also the parking brake pedal seems to catch way to close to the floor(within the last 2 or 3 clicks when applying)
Could thus be what's going on?
Q10: the brake light on the dash only ever comes on when the parking brake is applied.
Q11: the parking brake pedal does return all the way. But I'm starting to think I have the star wheels on the rear drums adjusted too far out. Also the parking brake pedal seems to catch way to close to the floor(within the last 2 or 3 clicks when applying)
Could thus be what's going on?
Rifleshooter
Well-Known Member
I never replaced the shoes or drums so yes.
I have seen a bunch of rear wheel cylinders (aka W/C) be the wrong diameter, right out of the box (non-Chrysler parts that is). It doesn’t happen often – but it does happen.
On problem cars (like this one), this is one of the things to check (W/C diameter). They are not hard to measure, out of the box – but on car, it require removal of one brake shoe (and pinch back boot), first).
Brake shoes are somewhat similar to 4-bbl carburetors, the brake shoe with most material goes to the rear (just like carburetor holes (secondary’s) are larger in the rear), and therefor work harder than the front half of drum brake shoes do.
Wet brake linings will make brakes grab. Leaking rear wheel cylinders and/or leaking rear axle seals can make brakes grab or lock up early) – which is opposite what one would think they will do.
A leak from either can be seen by fluid leaking out of the brake drum via looking at back side of rear wheels – but not in all cases.
Damaged brake metal lines is another thing that is hard to check. The first couple years of F-bodes, the front metal brake lines ran differently from any other Chrysler vehicle and are more acceptable to damage. I have even seen an engine install pinch the firewall mounted metal brake line and cause problems.
I have also seen a few metal brake lines have rust holes in them – in locations hard to see. A good flashlight, “dry” paper towel, a helper and patience is the only way to find rust-through, sometimes.
Another aid I use (which may or might not have been mentioned yet) is to test drive some place with dirt, gravel, sand, etc. (ie: non-paved road).
Use varying brake pressure to lock up at least one wheel, and get out and look at and measure each wheel – which will be fairly easy to determine which one(s) are not working.
Disk brake calipers do not return (much) on their own. They depend on wheel bearing play to push the brake pads away from brake rotor.
Try this: apply the brakes hard just as you are stopping for a brake inspection, keep holding it as car is placed in park, then release brake petal. Without touching car much/any thing else, get a floor jack and immediately jack up either side front wheel – off of the ground. Try to spin that tire. It will be hard to very hard to spin by hand – until spun a few turns and get easier (but not free). Disk brakes are great – but they do not have a good mechanism to push brake pads away from rotor.
On same note, if you take car for a drive and is able to stop and park the car without using the brake petal (parking brake works great), then jack up same tire in same procedure as above, that tire will spin as free as can be – because brake pads have been pushed away from rotor from normal driving.
Very rarely do proportioning valves/combination valves go bad. The only ones I have seen are ones that were left detached to brake lines for a while.
BudW
On problem cars (like this one), this is one of the things to check (W/C diameter). They are not hard to measure, out of the box – but on car, it require removal of one brake shoe (and pinch back boot), first).
Brake shoes are somewhat similar to 4-bbl carburetors, the brake shoe with most material goes to the rear (just like carburetor holes (secondary’s) are larger in the rear), and therefor work harder than the front half of drum brake shoes do.
Wet brake linings will make brakes grab. Leaking rear wheel cylinders and/or leaking rear axle seals can make brakes grab or lock up early) – which is opposite what one would think they will do.
A leak from either can be seen by fluid leaking out of the brake drum via looking at back side of rear wheels – but not in all cases.
Damaged brake metal lines is another thing that is hard to check. The first couple years of F-bodes, the front metal brake lines ran differently from any other Chrysler vehicle and are more acceptable to damage. I have even seen an engine install pinch the firewall mounted metal brake line and cause problems.
I have also seen a few metal brake lines have rust holes in them – in locations hard to see. A good flashlight, “dry” paper towel, a helper and patience is the only way to find rust-through, sometimes.
Another aid I use (which may or might not have been mentioned yet) is to test drive some place with dirt, gravel, sand, etc. (ie: non-paved road).
Use varying brake pressure to lock up at least one wheel, and get out and look at and measure each wheel – which will be fairly easy to determine which one(s) are not working.
Disk brake calipers do not return (much) on their own. They depend on wheel bearing play to push the brake pads away from brake rotor.
Try this: apply the brakes hard just as you are stopping for a brake inspection, keep holding it as car is placed in park, then release brake petal. Without touching car much/any thing else, get a floor jack and immediately jack up either side front wheel – off of the ground. Try to spin that tire. It will be hard to very hard to spin by hand – until spun a few turns and get easier (but not free). Disk brakes are great – but they do not have a good mechanism to push brake pads away from rotor.
On same note, if you take car for a drive and is able to stop and park the car without using the brake petal (parking brake works great), then jack up same tire in same procedure as above, that tire will spin as free as can be – because brake pads have been pushed away from rotor from normal driving.
Very rarely do proportioning valves/combination valves go bad. The only ones I have seen are ones that were left detached to brake lines for a while.
BudW
Rifleshooter
Well-Known Member
I'm not saying that my proportioning valve is bad or defective, I'm just saying that I think I remember loosening a bolt on it when I was replacing my w/c on both wheels. Maybe that has something to do with it but maybe not, aside from that the brakes do seem to grab incredibly fast on the rear. I was driving today and tried slowly pressing the brakes and I stopped feeling all brakes grab, but a hard/sudden brake made the rear lock up and feel like the front didn't apply hardly at all.
Where about on the car, was this "possibly" loosened bolt, located at?
Rifleshooter
Well-Known Member
Mounted to the rear where the brake line from the M/C splits into the 2 lines that go to each W/C.
That would be the rear brake hose.
There is a bolt that attaches the differential side of hose to the differential. It also has threads for both metal brake lines onto differential, going to each wheel cylinder.
Loosening the bolt will not affect anything, except for a possible differential lube oil leak from bolt being left loose (or missing).
Now the hose itself, can deteriorate externally and internally. Internal problems is one of the sources of brake problems.
IF any of the three rubber brake hoses show any sign of external cracking – replace ‘em! Especially as old as our cars are getting, if one is doing a repair in the area – just spend a few bucks more and replace the hose while there. A 10-20$ (US) hose is a lot cheaper than finding from end parts (like grills) because of a brake part failure.
The brake combination valve/proportioning valve bolts (actually a nut) to the L/F inner fender, just below the brake booster (if equipped)/brake master cylinder. The two short pieces of metal brake lines that come from the brake master cylinder, go directly to the brake combination valve.
BudW
There is a bolt that attaches the differential side of hose to the differential. It also has threads for both metal brake lines onto differential, going to each wheel cylinder.
Loosening the bolt will not affect anything, except for a possible differential lube oil leak from bolt being left loose (or missing).
Now the hose itself, can deteriorate externally and internally. Internal problems is one of the sources of brake problems.
IF any of the three rubber brake hoses show any sign of external cracking – replace ‘em! Especially as old as our cars are getting, if one is doing a repair in the area – just spend a few bucks more and replace the hose while there. A 10-20$ (US) hose is a lot cheaper than finding from end parts (like grills) because of a brake part failure.
The brake combination valve/proportioning valve bolts (actually a nut) to the L/F inner fender, just below the brake booster (if equipped)/brake master cylinder. The two short pieces of metal brake lines that come from the brake master cylinder, go directly to the brake combination valve.
BudW
Rifleshooter
Well-Known Member
I got around to having a look at the brake system all together and the splitter that mounts to the diff was tight, no leaks, the rear brake hose has no cracks showing, and the rear drums were adjusted properly all along. Aside from that I tightened the parking brake cable a bit and all if good there now. And yet even after checking the entire system, the fronts are still lazy as compared to the rear locking like there's no tomorrow. I'm lost
AJ/FormS
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Look RS, you keep saying things like I didn't this or that so it must be such and such. These are not good answers. And nobody can help you without the right answers. I gotta give Bud a lot of credit, cuz he is being so patient. He certainly has far more patience than I do.
This might help.
I would agree with AJ, there appear to be some questions either answered very broad (too broad) or not answered, yet.
BudW
I would agree with AJ, there appear to be some questions either answered very broad (too broad) or not answered, yet.
BudW
volare 77
Well-Known Member
Were the rear wheel cylinders leaking or just stuck or sticking? If they were leaking then the shoes could be contaminated . If it was my car i would have put on new shoes and turned the drums at least. Make sure the shoes are in the correct position and adjusted correctly. Previous owner could have installed they incorrectly.
Rifleshooter
Well-Known Member
When I replaced the wheel cylinders the left rear was leaking which is what caused me to need to replace it. I replaced both of them while I was at it. As for the shoes I regrettably didn't think to take notice of their condition and placement. I'll be sure to take a closer look next time I have the chance. How would I be able to tell if the shoes and or star adjuster is facing the right way, in the right place, and operating properly?
Rifleshooter
Well-Known Member
I thought I've answered all the questions sorry. Which ones have yet to be answered and or need a more precise answer?
I might have a picture of how your drum brake hardware should be - but I need to know what year car, you have (there are some differences of the hardware over the years).
Rifleshooter
Well-Known Member
1980 Plymouth Volare Duster with a 7 1/4 rear, 2.76 gear, and drums, I don't know how big around. Lug pattern 5x4.5. Hope I got it all.
AJ/FormS
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Hey I got one of those,lol, and with perfect working brakes. And it skids the front tires, even at 30mph.and not even using max pedal-pressure.
I'm pretty sure your M/C is hydraulically locked, but Bud will get you to the why of it, and how to get past that.
You can't find a better man than Bud to fix you up.
But you know what they say about computers right? Garbage in/garbage out. If you keep feeding him BS answers, he can't do his job. And Bud is way to nice a man to call you on your bs answers. He'll just keep coming at you from different directions, until he gets what he needs. As mechanics, many time we are really fishermen, fishin for the answers we need to hear to make a thing official. So if this seems to be taking a long time to resolve, don't blame the fisherman.
In the meantime, I urge you to get the rear wheels off, and the drums off and take/post pictures from angles that show at least one shoe fully and the parking brake mechanism;Both sides.
If you had a leaky W/C follow the trace of the fluid. It wouldda found it's way to the bottom of the backing plate, then dripped onto the drum. Of course you didn't notice this at the first drip, did you? No, you probably drove around like this until you noticed the low fluid level. That means with every brake application,You were spreading that brake fluid all around the drum, and of course the shoes were the spreader and the mop. So this diagnoses only needs to take as long as you make it take.
Pictures are worth, in your case, hours and hours
I'm pretty sure your M/C is hydraulically locked, but Bud will get you to the why of it, and how to get past that.
You can't find a better man than Bud to fix you up.
But you know what they say about computers right? Garbage in/garbage out. If you keep feeding him BS answers, he can't do his job. And Bud is way to nice a man to call you on your bs answers. He'll just keep coming at you from different directions, until he gets what he needs. As mechanics, many time we are really fishermen, fishin for the answers we need to hear to make a thing official. So if this seems to be taking a long time to resolve, don't blame the fisherman.
In the meantime, I urge you to get the rear wheels off, and the drums off and take/post pictures from angles that show at least one shoe fully and the parking brake mechanism;Both sides.
If you had a leaky W/C follow the trace of the fluid. It wouldda found it's way to the bottom of the backing plate, then dripped onto the drum. Of course you didn't notice this at the first drip, did you? No, you probably drove around like this until you noticed the low fluid level. That means with every brake application,You were spreading that brake fluid all around the drum, and of course the shoes were the spreader and the mop. So this diagnoses only needs to take as long as you make it take.
Pictures are worth, in your case, hours and hours
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Rifleshooter
Well-Known Member
When you say that the M/C might be hydrolically locked what exactly do you mean? Also I am very appreciative of all the help ive gotten from BudW ever since I first started on this website and he's helped me in more than one occasion. I apologize to all about bs answers in the previous responses and will do my best to give better answers to questions. You're right about what happened with the leaking W/C and not noticing until I was low on brake fluid. I'll be sure to take many pictures and post them the next time I have my wheels off.
