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71 Dart Drum brake problems
#1126251
12/02/11 06:53 PM
12/02/11 06:53 PM
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Joined: Mar 2003
Posts: 4,848
Memphis
HemiRick
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Memphis
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This is a 47ooo mile very original car.
The front drum brakes will not lock up, they work but not effectively enough. In a normal stop on dry pavement the rear brakes LOCK UP 1st.
Everything has been checked. The shoes are new and so is the hardware and brake hoses. The brake pedal has excellent height.
I think this is a prop valve problem but my understanding is that a 4 drum car only has a brake waring light valve but it does no proportioning. Am I wrong?
Anyone know what size the wheel cylinders should be? Front 9 inch drums. Manual brakes not power.
Last edited by HemiRick; 12/02/11 07:00 PM.
Take care,
Rick
68 Coronet R/T 440 & 68 Charger 528 Hemi,and 5 Challengers! 6 cyl, 318, 360, 383, 451
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Re: 71 Dart Drum brake problems
[Re: HemiRick]
#1126252
12/02/11 06:57 PM
12/02/11 06:57 PM
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Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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Pretty sure no proportioning. Would need smaller rear wheel cyls for less rear bias. Ebooger used to sell (7/8" iirc) ones for reasonable money. Some semi met front shoes might be a faster/cheaper partial solution. EDIT might tighten the fronts to where when you hand spin the front wheel(s) (forward) you hear a slight "tick" at one point in the revolution and tighten the rears to that point for an equal reference then loosen the rears a # of clicks. Check your pedal reserve (height) when done
Last edited by RapidRobert; 12/02/11 07:24 PM.
live every 24 hour block of time like it's your last day on earth
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Re: 71 Dart Drum brake problems
[Re: RapidRobert]
#1126253
12/02/11 07:45 PM
12/02/11 07:45 PM
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Joined: Mar 2003
Posts: 4,848
Memphis
HemiRick
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The brakes are all freshly adjusted by me and are just off the drums. The master cyl. is old but the pedal height is very good. This is just baffling to me. The car does not stop well, something is causing the fronts to not work well and I'm stumped. It's just like it has old clogged brake hoses but they are new.
The amount of pedal pressure required to make the rears lock up is not excessive and seems normal and the pedal is way off the floor.
Last edited by HemiRick; 12/02/11 07:47 PM.
Take care,
Rick
68 Coronet R/T 440 & 68 Charger 528 Hemi,and 5 Challengers! 6 cyl, 318, 360, 383, 451
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Re: 71 Dart Drum brake problems
[Re: HemiRick]
#1126254
12/02/11 08:46 PM
12/02/11 08:46 PM
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Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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Might take off the front drum (as you know closest to firewall) line from the M/C and take the hard lines off of the hoses at each front frame tab & blow thru em to see if they're clear. Before doing that tho, w the front wheels off the ground & a helper playing w the pedal and you spinning the tires forward by hand do the fronts lock solid from spinning in the air? M/C rear (front brakes) piston/seal might be poor), inadequate psi. Holler back w you can
live every 24 hour block of time like it's your last day on earth
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Re: 71 Dart Drum brake problems
[Re: RapidRobert]
#1126256
12/02/11 09:27 PM
12/02/11 09:27 PM
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Joined: Mar 2003
Posts: 4,848
Memphis
HemiRick
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OP
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With the front end off the ground and pressure on the pedal the front brakes do work. You cannot turn the wheels by hand. But a stop in gravel at 10 MPH does not lock up the fronts, while the rears will skid 10 ft.
I'm thinking any MC problems would show up in the pedal height and it's excellent. MC's are cheap and after I visually inspect and blow the lines, this may be the next thing to try.
Take care,
Rick
68 Coronet R/T 440 & 68 Charger 528 Hemi,and 5 Challengers! 6 cyl, 318, 360, 383, 451
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Re: 71 Dart Drum brake problems
[Re: HemiRick]
#1126257
12/02/11 09:34 PM
12/02/11 09:34 PM
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Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
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Posts: 36,041
Lincoln Nebraska
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How are you thinking that if the seal on that piston was bad that it would change/affect the pedal height?
live every 24 hour block of time like it's your last day on earth
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Re: 71 Dart Drum brake problems
[Re: RapidRobert]
#1126258
12/02/11 09:37 PM
12/02/11 09:37 PM
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Joined: Mar 2003
Posts: 4,848
Memphis
HemiRick
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Because every bad master I've ever seen in 35 yrs of fixin cars had bad pedal height or a sinking pedal and this pedal is firm and high. Also if half the master were bad it should turn on the brake warning light.
Last edited by HemiRick; 12/02/11 09:39 PM.
Take care,
Rick
68 Coronet R/T 440 & 68 Charger 528 Hemi,and 5 Challengers! 6 cyl, 318, 360, 383, 451
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Re: 71 Dart Drum brake problems
[Re: GO_Fish]
#1126260
12/02/11 10:08 PM
12/02/11 10:08 PM
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Joined: Mar 2003
Posts: 4,848
Memphis
HemiRick
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There is definately something wrong, to drive this car in the rain would be deadly.....It would have a huge problem, it is very noticable on dry pavement stopping at normal rates too.
Take care,
Rick
68 Coronet R/T 440 & 68 Charger 528 Hemi,and 5 Challengers! 6 cyl, 318, 360, 383, 451
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Re: 71 Dart Drum brake problems
[Re: RapidRobert]
#1126263
12/02/11 10:44 PM
12/02/11 10:44 PM
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Joined: Mar 2003
Posts: 4,848
Memphis
HemiRick
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I was just about to post the exact same thought that the problem has to be between the master and the splitter block because it doesnt pull and affects both front wheels equally.
Take care,
Rick
68 Coronet R/T 440 & 68 Charger 528 Hemi,and 5 Challengers! 6 cyl, 318, 360, 383, 451
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Re: 71 Dart Drum brake problems
[Re: HemiRick]
#1126264
12/02/11 10:51 PM
12/02/11 10:51 PM
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Joined: Mar 2010
Posts: 1,880
Out in Left Field, NY
bobs66440
top fuel
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top fuel
Joined: Mar 2010
Posts: 1,880
Out in Left Field, NY
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Quote:
This is a 47ooo mile very original car.
The front drum brakes will not lock up, they work but not effectively enough. In a normal stop on dry pavement the rear brakes LOCK UP 1st.
Everything has been checked. The shoes are new and so is the hardware and brake hoses. The brake pedal has excellent height.
I think this is a prop valve problem but my understanding is that a 4 drum car only has a brake waring light valve but it does no proportioning. Am I wrong?
Anyone know what size the wheel cylinders should be? Front 9 inch drums. Manual brakes not power.
You shouldn't have a proportioning valve. Just a shuttle valve in the distribution block to trip the warning light. It's designed to move to the low pressure side (front/rear) in case of a leak. It's normally self-centering as long as everything is working properly. It could be that it's stuck partially blocking the front line port, thus cutting the pressure.
Are the drums new also? Or have they been turned? What shoes are they? I have had this same problem with my last two cars and both were traced to shoe/drum/pad issues.
I had exactly the same issue with my '70 Mustang (disc front brakes, but using this to make a point). No matter what I did, I couldn't get that car to lock the fronts. EVERYTHING was new. I even got very expensive cold stopper pads from Ca. In the end I went to AutoZone and got a set of $18 pads. Bang! Fixed. It may be as simple as brake shoe compound or having the drums turned.
You can also use a brake pressure gauge to check the pressure going to the wheel cylinders.
I'm showing 1" bore wheel cylinders for the 9" drums.
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Re: 71 Dart Drum brake problems
[Re: bobs66440]
#1126265
12/02/11 11:21 PM
12/02/11 11:21 PM
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Joined: Mar 2003
Posts: 4,848
Memphis
HemiRick
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Quote:
Just a shuttle valve in the distribution block to trip the warning light. It's designed to move to the low pressure side (front/rear) in case of a leak. It's normally self-centering as long as everything is working properly. It could be that it's stuck partially blocking the front line port, thus cutting the pressure.
This fits the existing theory and would explain the high firm pedal, if the fluid has no where to go the pedal would be great. Tommorrow I will remove and inspect the lines from the master to the splitter and the brake valve.
Take care,
Rick
68 Coronet R/T 440 & 68 Charger 528 Hemi,and 5 Challengers! 6 cyl, 318, 360, 383, 451
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Re: 71 Dart Drum brake problems
[Re: HemiRick]
#1126266
12/02/11 11:32 PM
12/02/11 11:32 PM
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Joined: Mar 2010
Posts: 1,880
Out in Left Field, NY
bobs66440
top fuel
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top fuel
Joined: Mar 2010
Posts: 1,880
Out in Left Field, NY
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Quote:
Quote:
Just a shuttle valve in the distribution block to trip the warning light. It's designed to move to the low pressure side (front/rear) in case of a leak. It's normally self-centering as long as everything is working properly. It could be that it's stuck partially blocking the front line port, thus cutting the pressure.
This fits the existing theory and would explain the high firm pedal, if the fluid has no where to go the pedal would be great. Tommorrow I will remove and inspect the lines from the master to the splitter and the brake valve.
The valve is very simple, but be very careful. I've never had a Mopar one apart, but the Ford ones have lots of o-rings and springs and little pieces that can fly around the room.
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Re: 71 Dart Drum brake problems
[Re: bobs66440]
#1126267
12/03/11 12:16 AM
12/03/11 12:16 AM
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Joined: Feb 2005
Posts: 5,221
Branson, Mo.
joedust451
super gas
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super gas
Joined: Feb 2005
Posts: 5,221
Branson, Mo.
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Rick, I had about the same problem with my 71 swinger with 4 wheel drum, If you haven't already tried this, Loosen up the back brake shoes, When you have front disc, it is proportioned by a valve, On 4 wheel drums there not, In most cases, you'll never be able to get the front drums to lock up unless its 1 wheel, then it can, but it'll normally yank to 1 side hard & scare the crap out of you  , But the rears will lock up, especially if there not evened up F&R, Try this & give it a road tast, let us know. If the peddle is nice & high & firm without sinking & the front brakes are holding, you shouldn't have an air issue & the MC is working.
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Re: 71 Dart Drum brake problems
[Re: joedust451]
#1126268
12/03/11 12:56 AM
12/03/11 12:56 AM
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Joined: Mar 2003
Posts: 4,848
Memphis
HemiRick
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The car stops poorly all ready and you want me to make the rear brakes work worse. No thanks. I'll stick with fixing the problem in the fornt.
Take care,
Rick
68 Coronet R/T 440 & 68 Charger 528 Hemi,and 5 Challengers! 6 cyl, 318, 360, 383, 451
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Re: 71 Dart Drum brake problems
[Re: HemiRick]
#1126269
12/03/11 01:30 AM
12/03/11 01:30 AM
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Joined: Feb 2005
Posts: 5,221
Branson, Mo.
joedust451
super gas
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super gas
Joined: Feb 2005
Posts: 5,221
Branson, Mo.
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Quote:
The car stops poorly all ready and you want me to make the rear brakes work worse. No thanks. I'll stick with fixing the problem in the fornt.
Your not going to get the car to act like it has disc brakes, drum brakes alway stop poorly, plus your asking for opinions because you don't know what the problem is, i'm only trying to help as i've had this problem before on other drum brake cars, i'm not telling you to loosen the crap out of them, all it takes is backing them off a bit thats all or tighten up the fronts, its not rocket sience, just trial & error, but you do what you want.
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Re: 71 Dart Drum brake problems
[Re: joedust451]
#1126270
12/03/11 01:33 AM
12/03/11 01:33 AM
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Joined: Mar 2003
Posts: 4,848
Memphis
HemiRick
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Memphis
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Drum brake cars stop just fine, comparable to a disk brake car, when when everything is working. They just dont stop twice in rapid succession from high speed, like a disk brake car will.
Take care,
Rick
68 Coronet R/T 440 & 68 Charger 528 Hemi,and 5 Challengers! 6 cyl, 318, 360, 383, 451
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