Bad booster?

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hula

hula

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72 Dart with 340 power discs, new calipers bled etc. Pedal was getting hard before replacing pads etc. Pedal still hard and motor pulling about 14 inHg vac at idle so increase idle and vacuum and doesn't help. Sometimes when you push on pedal it increases idle speed so is there a vac leak in booster? I tried hooking a hand pump vacuum on the check valve port and I can not pull any vacuum at all. In the pic the motor is off and I also blocked the port to the manifold with my finger trying to pull hand vac on it also.

IMG_5378.JPG
 
Well of course the booster is bad, all the symptoms are there and you vac checked it. LOL

Make sure that check valve works , isn't it a one way valve....
 
Yep sounds like you need a booster. That's not gonna be cheap. Most NAPA stores can send yours out and rebuild it.
 
Testing w/ a manual hand pump might be inconclusive, at least I recall trying once, couldn't pump a vacuum, yet booster was OK. Once you remove and before you send it off, test it by hand. Connect it to the intake of another vehicle, which known good vacuum. Push in the pedal rod. The output rod should follow your motion. You will hear a hiss as it moves. When you push in the pedal rod, it leaks in air on that side which makes the forward force. When you stop moving, the hiss should stop. Most commonly, the rubber diaphragm fails where the vacuum port connects. Fumes from the engine attack the rubber, and it probably doesn't like the ethanol in today's gas. Happened to me even though I installed a charcoal filter in the vacuum hose. The diaphragm was hard and brittle at the port and cracked. The rest of the rubber was like new.
 
The simple test. Cut and dried.
Exhaust booster by cycling pedal a few times. With foot on brake pedal start car. If pedal drops,say an inch for example then booster is good.
 
Tooljunkie said:
The simple test. Cut and dried.
Exhaust booster by cycling pedal a few times. With foot on brake pedal start car. If pedal drops,say an inch for example then booster is good.
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Yeah did the pedal test and didn’t drop. Sent it off to Dewey boosters in Oregon to rebuild because for some reason Dart boosters went extinct. LoL
 
hula said:
Yeah did the pedal test and didn’t drop. Sent it off to Dewey boosters in Oregon to rebuild because for some reason Dart boosters went extinct. LoL
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Yes they are. I have a good looking one that needs rebuilt but I scored a good one last year. Some parts are getting hard to come by but then again our cars are getting old. That's what makes them so cool :)
 
Haven't seen a new one available in years. Remanufactured is all your gonna get.
 
I had the hard pedal almost no brakes problem recently and sent the booster to ‘Booster Dewey’. It came back looking like new. I installed a master cylinder from Dr Diff in front of it and now the brakes work again.
 
Slowswinger said:
I had the hard pedal almost no brakes problem recently and sent the booster to ‘Booster Dewey’. It came back looking like new. I installed a master cylinder from Dr Diff in front of it and now the brakes work again.
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Yeah when I got it back the brakes were ok, but not optimal so I called him and he said it takes 20 inHg to operate it efficiently and I had 14-15 so I opted to use a vacuum canister and hide it. How much vacuum do you have? Have a cam?
 
Wow I'm running this cam Voodoo Hydraulic Flat Tappet Cam - Chrysler 273-360 268/276 - Lunati Power in a 360 with 9.5 to 1 compression and my brakes work great. I'm no were near 20". I don't think you could get 20" of vacuum unless you were closed throttle going down hill. Most cars have about 19" at idle. Where did he get that number? Your 15" should be plenty with a small booster.
 
hula said:
Yeah when I got it back the brakes were ok, but not optimal so I called him and he said it takes 20 inHg to operate it efficiently and I had 14-15 so I opted to use a vacuum canister and hide it. How much vacuum do you have? Have a cam?
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I did not measure the vacuum but will post it this weekend. I assume the cam is the original that came in the slant six. The booster worked great before I had the hard pedal problem, I figured the booster finally gave up after 46 years.
 
My uncalibrated harbor freight vacuum gauge shows 18" of vacuum. Between the rebuilt booster and the new master cylinder I have more braking power than I ever did before.
 
I wish somebody sold kits to rebuild a booster. They are fairly simple inside and the Midland-Ross ones w/ a V-clamp are easy to disassemble (Bendix is tougher). Shipping the whole booster back and forth gets expensive, whereas a parts kit would be small. I think if one just had the rubber diaphragm, it could be replaced on the metal piston. I once cut thin neoprene sheet to make my own, but it didn't have the proper folds. It worked, but I scored a rebuilt booster cheap on rockauto so used that. Since, I found the leftover neoprene sheet stock cracked thru, so expect it won't last in the booster. A better rubber, formed correctly would be great. Otherwise, the only other part to replace is the "air valve", which is a packaged unit and can sometimes be found on ebay, and some sliding seals on the input shafts.
 
Looks like there are rebuild kits...Found ones offered by Harmon Brakes.
Has anyone had experience using a "Harmon Classic Brakes" company brake booster rebuild kit for a 1967-69 a body (O.E. Mopar booster by Midland)?..

I am weighing the pros and cons of buying a rebuild kit vs having a specialty rebuild shop do it for me.

There is a shop in Portland, OR. called "Power Brake Booster Exchange". It is a 6 hour round trip drive but I am planning on driving it for another reason. Looks like there are some mixed reviews of their work in this thread...

Looks like the list price to have it done at the shop starts at around 170. if you have a core or to buy the rebuild kit would run me 225. so the shop appears to be the better value without having checked on what extra charges the shop may want to charge. (not to mention the diy work/time)
 
Fishing68 said:
There is a shop in Portland, OR. called "Power Brake Booster Exchange". It is a 6 hour round trip drive but I am planning on driving it for another reason. Looks like there are some mixed reviews of their work in this thread...
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Where's the mixed review? Nothing wrong w Booster Dewey's work. They have a stellar reputation. Used them myself for my 69 Bendix booster.
 
I've had my local NAPA store rebuilt a few is the past. It was about 200 bucks. Looks like new and worked great. Turn around was about a week if I remember correctly.
 
From: DEMONIC- "Where's the mixed review? Nothing wrong w Booster Dewey's work. They have a stellar reputation. Used them myself for my 69 Bendix booster."

Answer to DEMONIC: See post # 16 in this thread from: HULA - Yeah when I got it back the brakes were ok, but not optimal so I called him and he said it takes 20 inHg to operate it efficiently and I had 14-15 so I opted to use a vacuum canister and hide it. How much vacuum do you have? Have a cam?
 
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