Brake booster bad??
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Junior User
Joined: May 2003
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Brake booster bad??
86 F250 Diesel. Did things backwards. Replaced the vac pump, then ran this test ( http:///showphoto.php?photo=10952&pa...ium&thecat=500 ).
Vacuum is good at 23" tested at the end of the booster line. But when I connect the vac hose to the booster and "T" off the main line with my guage, I get about 11" and the needle is bouncing around quite a bit. I then plugged off ALL the accessories, so basically it's the pump connected straight to the booster. I get the same thing... 11". When I step on the brake pedal, the vacuum very gradually increases to about 15" with the needle still vibrating a lot. It seems to me that there is a leak in the booster. Any ideas?
Thx,
Sam
Vacuum is good at 23" tested at the end of the booster line. But when I connect the vac hose to the booster and "T" off the main line with my guage, I get about 11" and the needle is bouncing around quite a bit. I then plugged off ALL the accessories, so basically it's the pump connected straight to the booster. I get the same thing... 11". When I step on the brake pedal, the vacuum very gradually increases to about 15" with the needle still vibrating a lot. It seems to me that there is a leak in the booster. Any ideas?
Thx,
Sam
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Junior User
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Gee I don't know which automatic tranny I have. But like I said, I isolated everything except the pump and the booster, so I'm not sure how that would come into things.
PUMP --------------- GAUGE = 23"
PUMP ------------------GAUGE T'd----------- BOOSTER
GAUGE 11" Fluctuating wildly
Every other hose disconnected.
PUMP --------------- GAUGE = 23"
PUMP ------------------GAUGE T'd----------- BOOSTER
GAUGE 11" Fluctuating wildly
Every other hose disconnected.
Post Fiend
Joined: Nov 2004
Posts: 5,638
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From: Manitoba
Then the booster would be suspect like you say according to your test..............but the vacuum should be steady. Could it be pump has too direct a line of vacuum. Hook everything back up as normal with the vac guage Td in.
Last edited by PLC7.3; Jan 14, 2005 at 05:19 PM.
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Yeah I still get exactly the same thing. In fact that's how I started (with all the accessories connected). Then I one by one removed a vac line and plugged it until all I had left was the booster and the pump.
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i can hear the vacuum pump going chh chh chh chh chh chh when its idling and the booster is plugged in, then i unplug the booster and put my finger on the line, the chh chh stops. i am just guessing that my booster is bad like yours. i am going to wait till i can get a hydraulic booster off a super duty and hook it up to my truck. truck gets real hard to stop when trying to stop suddenly or after making a turn or pressing the brake twice in a row real fast. and i have a roblem with air getting into my lines somehow, i can't figure that one out and nobody i ever have talked to has ever figured it out either. i have NO leaks, but i can bleed my brakes and they work fine for a week or so, then the air gets back in there. its in the back brakes only. that is another reason i want the hydraulic booster instead of the vacuum. i got a chevy with a hydro booster and the brakes work good, but i can still mash the edal to the floor with ease, where as with a vacuum booster, you can't get the edal all the way even with the booster helping. but i would say your booster is bad.
Elder User
Joined: Sep 2004
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From: Peoria IL
Just replaced my booster. Took about 30 minutes. I had to replace my vac pump and the brakes worked great until I fixed my aluminum pedal housing and that somehow messed up my booster. It broke a seal from moving the linkage too much putting in that dam alum bracket.
When the seal was broke I could hear air leaking from the booster at all times unless i had my foot on the brake.
When the seal was broke I could hear air leaking from the booster at all times unless i had my foot on the brake.
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Well just to finish this story, it turned out that my booster was bad. It must have had a huge leak in it. As I said, I got about 3" of vacuum on the accessory ports when everything was connected. This was a booster I replaced 1 year and 1 month ago (1 year warranty!). I brought it back to Napa with my receipt and they had mercy on me and honored the warranty.
Installed the new pump and now I get 23" everywhere, and the brakes are so damned powerful it's unbelievable! In fact, I think this booster never worked properly. The last half year or so I was using both feet on the brake pedal to stop. Now you just tap the pedal and you damn near go through the windshield.
By the way, there is a flaw in that procedure at the dieselstop.com website. There should be a step before A6 that says to plug all accessory lines so that the pump is in effect connected directly to the booster (with the guage T'd in). If vac is good, go to A6. If not, booster is bad.
Installed the new pump and now I get 23" everywhere, and the brakes are so damned powerful it's unbelievable! In fact, I think this booster never worked properly. The last half year or so I was using both feet on the brake pedal to stop. Now you just tap the pedal and you damn near go through the windshield.
By the way, there is a flaw in that procedure at the dieselstop.com website. There should be a step before A6 that says to plug all accessory lines so that the pump is in effect connected directly to the booster (with the guage T'd in). If vac is good, go to A6. If not, booster is bad.
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i just replaced my vacuum booster with a hydraulic one off a 95 super duty. i think it is the best thing i ever did to my truck. like you said, i have almost thrown myself through the windshield a few times after getting used to mashing the brake 1/2 way to the floor before they started working. i don't know if the stock master cylinder will fit on that hydro-booster, but i used the super duty master was bigger than the stock one and i bought it for only 25 bucks along with the $100 hydrobooster. looks and fits like it was meant to be there, 45 mins installation. if you do this, make sure you get the lines that go to the power steering pump and the p.s. gearbox.
