power brake booster

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gunmetal72

gunmetal72

Life is a dark ride
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The brake booster on my 72 Duster is not working properly, Has anyone rebuilt one or is it better just to buy a replacement?
 
I went through this recently. Rebuild was about twice as much as a reman replacement from napa (although I get a discount there). I can try and look and find the part number. Not sure if it will fit yours though. My 72 Scamp has the 73-76 power disc front/drum back setup on it. Not sure if you have the same booster.
 
I think the booster is a little different from 72 to 73. Not sure if the are interchangeable or if I would need to change the bracket. I will post a pic

DSCN3202.JPG
 
I checked at NAPA about 2 yrs ago, and they said nothing was available as a stock replacement. You could try Rock Auto, but don't know if you will do any good. I would say, look in the Hemmings Motor News under "Services Offered" and see about a rebuilder like Booster Dewey, it will probably be pricey, will be done right, and should last your car a lifetime.
 
Dodge33 said:
I checked at NAPA about 2 yrs ago, and they said nothing was available as a stock replacement. You could try Rock Auto, but don't know if you will do any good. I would say, look in the Hemmings Motor News under "Services Offered" and see about a rebuilder like Booster Dewey, it will probably be pricey, will be done right, and should last your car a lifetime.
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i just put a booster and master cyl. from a 74 dart on my 72 brackets. worked fine. i think it ran me 135 bucks at orielys.
 
I don't know what years boosters changed from Midland-Ross to Chrysler or other. I can say many owners have sent their Midland-Ross 2 stage boosters off for rebuild and were pleased with results.
My memory says, "Booster Dewey" was their service provider. Hope this helps
 
Send yours to Booster Dewey - you won't be disappointed!
 
I want to make sure it is the booster and I think it should hold vacuum after I turn off the engine but when I pulled off the hose coming from the intake, there was no vacuum left in the booster. Hose was pulled off the booster about 10 sec after the engine was turned off. So, does this mean the booster is done?
 
gunmetal72 said:
I want to make sure it is the booster and I think it should hold vacuum after I turn off the engine but when I pulled off the hose coming from the intake, there was no vacuum left in the booster. Hose was pulled off the booster about 10 sec after the engine was turned off. So, does this mean the booster is done?
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The brake booster is only vacuum assisted when the engine is in the running mode. When the engine is off, there won't be any vacuum left in the booster, basically like a household vacuum work's. Hope this help's you some.
 
Check the check vale to make sure it is good first, might be bad and even if it is the booster should work when the engine is running unless you have a cam.
 
Yes I have a mild cam in it, but even when I am driving it the breaks are poor, I have push hard on the pedal. One the first push of the pedal, I can feel a little bit of assist but it gets hard to push in a few seconds. I checked the valve and it holds pressure, seems ok. Do I just need to add an additional vacuum can
 
I have a big cam and had to go with a pump actually. My vac at idle is 5-8. Easy test for the check valve is just pull it from the booster then blow through it in both directions it should only go one way. If you can get a hand held vac pup hook it to the booster some how and see if there is a leak if so its the booster. Might take a while to pump it up so be patient, big volume to overcome.
 
I think your booster is different than mine. But I'll check when I'm working on it tomorrow.

How mild is your cam? Do you know your vacuum at idle? If you're running power brakes and steering you want at least 10 inches of vacuum at idle. 12 or more is better. If you don't know your vacuum can you tell us what cam and we can try and find out. Pushing hard means you're into the "manual" part of the brakes. I occasionally have to do this when backing up or something, due to low vacuum. It could be a bad booster or not enough vacuum.
 
Definitely check it with a vac gauge, kind of sounds like mine when I let off the gas the vac went up and had one good stop in it. Two with a separate reservoir!
 
To test the booster, pump the pedal 5-10 times when not running, to get rid of all of the residual vacuum. Then, while holding the brake pedal, start the engine and see if the pedal sinks further down when the engine starts; this shows that the booster is properly reacting to engine vacuum.

The check valve should hold some vacuum in the booster. Another way to test if the booster is holding vacuum is to idle the engine, check how far the brake pedal goes down with moderate force, then release the pedal and then shut the engine off off. Then push on the brake pedal with the same force and the pedal should go down to the same approximate position. Push the pedal down a few more times, and it should start not pushing down as far, and get harder to push; this is an indication that the residual vacuum in the booster is being bled off by successive pedal actuations and eventually going away.

If there is no difference in pedal travel with the same moderate pedal force when idling, and then after several pedal actuations when shut off, then the booster is not working, or you have an inadequate vacuum supply.

One thing to to check is that the air opening on the pedal side is clear. This is often a filter felt around the pedal rod area. The can become clogged and block airflow to the pedal side of the booster diaphragm, and acts the same as no vacuum. On some cars, this can be serviced externally, but I am not sure if this is the case on the Mopar units.
 
The best is to throw a gauge on it. Then check the booster for leaks before over thinking it and throwing money at it for nothing. Tell you the truth I wish I knew of the "hydra-boost?" systems I would have gone that direction the pump and extra vac can takes up a lot of room under the hood.
 
My application is different then most also it is a 440 in a dart 4 wheel disk and a 8"booster.
 
My experience with that booster and a 292/509 is not good. With a 223@.050 it was not bad. With a 230@.050 I threw it in the corner for a bigger one off a 73 Dart.
The check valve, if good, should easily hold enough vacuum for at least one stop from 60mph with the engine shut off.Sometimes they hold vacuum for at least 10 minutes after the engine is shut off.
I fear yours has a bad diaphragm, or a bad control valve, or the pushrod adjustment is preventing the control valve from seating.
If your engine runs rough with the brake applied,or the idle jumps around when you pump the pedal,it may be sucking air through a perforated diaphragm.If no change, then I would loosen the booster and space it towards the rad, about a quarter of an inch and let it sit there, at it's normal attitude.Hang it from the underside of the hood if you need to, or block it up. Then charge the booster by running the engine for a half a minute or more, at fast idle. Shut it off, and wait for ten minutes; then check for vacuum, by manipulating the check-valve. If none found I would assume the control valve is bad.
I am much happier with the large diameter single diaphragm.
 
AJ/FormS said:
My experience with that booster and a 292/509 is not good. With a 223@.050 it was not bad. With a 230@.050 I threw it in the corner for a bigger one off a 73 Dart.
The check valve, if good, should easily hold enough vacuum for at least one stop from 60mph with the engine shut off.Sometimes they hold vacuum for at least 10 minutes after the engine is shut off.
I fear yours has a bad diaphragm, or a bad control valve, or the pushrod adjustment is preventing the control valve from seating.
If your engine runs rough with the brake applied,or the idle jumps around when you pump the pedal,it may be sucking air through a perforated diaphragm.If no change, then I would loosen the booster and space it towards the rad, about a quarter of an inch and let it sit there, at it's normal attitude.Hang it from the underside of the hood if you need to, or block it up. Then charge the booster by running the engine for a half a minute or more, at fast idle. Shut it off, and wait for ten minutes; then check for vacuum, by manipulating the check-valve. If none found I would assume the control valve is bad.
I am much happier with the large diameter single diaphragm.
Click to expand...
So are you saying the cam I am using is not good for power brakes? I am not that knowledgeable when it comes to cams and vacuum
 
The booster in post 3 is a "dual diaphragm" type. One I took from a 74 Dart slant was a larger OD single diaphragm Midland-Ross type. It will boltup fine your brackets, but may not clear the valve cover, especially w/ a 440.

You can test your booster by supplying it vacuum from another car that is idling. I have done that to test one in the air and verify it follows motion of the input rod and don't hear leaking from a ruptured diaphragm or stuck pedal valve.

Finding them on rockauto can be hit or miss. I jumped on one for my 65 Newport that showed up for ~$80 clearance w/ MC. They had shown none for years. Came in a dusty box, bolted up and worked fine. Before that, I had drilled holes to mount the 74 one. Booster Dewey can often supply one, but not cheap. I have never seen rebuild kits, though that would be easy for a M-R type. I did so by cutting neoprene rubber sheet and it worked - in air, haven't run on a car.

You can also use a newer booster. I installed one for a 95-99 Breeze w/ ABS MC on Dart brackets. Intrepid boosters look the same (not the MC). I did have to rat-tail file the bracket holes slightly.
 
Your money, your choice. One year warranty. 3, 5, 10, year later who will be willing to rebuild it if they don't even know what it is. and brake fluid on chrome hasn't worked out well in most cases. those purdy chrome master cylinder covers are short lived.
 
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