Vaccum Pump suction
New User
Joined: Feb 2001
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Vaccum Pump suction
Can anyuone tell me how to properly test the vaccum pump on my 6.9 and how much vaccum I should be producing? The brakes don't perform as they should. They just don't have the power they once did. I can't lock 'em up even if I wanted to. I've replaced everything but the brake booster and vaccum pump. The low vaccum indicator appears to be operating properly and does not indicate loss of vaccum at anytime.
Thanx, K
85 ford f-250 6.9 extended cab 4x4 w/automatic
Thanx, K
85 ford f-250 6.9 extended cab 4x4 w/automatic
More Turbo
Joined: Nov 2000
Posts: 715
Likes: 11
From: Erie, PA
Vaccum Pump suction
I have the exact same problem with my brakes. I have no idea what it could be. I have also replaced everything but rotors, drums, and brake booser. The next thing I will try is the rotors, they are very thin.
To check the vacuume pressure you will need to rent or buy a vaccume gauge. I can only pump my brakes 4 times before I loose all the boost pressure. One mechanic told me that on a diesel, there is no place to "Store" the vacuume that is produced. On a gas engine all the vacuume is stored in the intake manifold.
1986 F-250 6.9 diesel,4x4,XLT Lariat,Ex Cab, 8'bed,etc...
To check the vacuume pressure you will need to rent or buy a vaccume gauge. I can only pump my brakes 4 times before I loose all the boost pressure. One mechanic told me that on a diesel, there is no place to "Store" the vacuume that is produced. On a gas engine all the vacuume is stored in the intake manifold.
1986 F-250 6.9 diesel,4x4,XLT Lariat,Ex Cab, 8'bed,etc...
New User
Joined: Feb 2001
Posts: 5
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Vaccum Pump suction
The brake booster has a check valve to store vaccum inside the booster. But like any other vehicle, if the vaccum source is lost (ie hose breaks or engine dies), you will only have enough vaccum stored in the brake booster for one or two stops. After that, you better some real strong legs or a lot of room to stop. You'll need it.
I have a vaccum guage and am looking for the specs on the pump. I'm currently getting about 7 in/hg. What I need to know is, while this amount is adequate to keep the low vaccum indicator off, is it adequate for optimal brake operation.
Also how do I troubleshoot a vaccum pump or brake booster problem besides replacing them and noting the results.
One other development, last week I developed a leak in one of the power steering hoses. Probably the return hose. While troubleshooting the problem I noticed a hissing sound coming from the brake booster. I think it may be a stuck check valve. As such I'll probably replace the brake booster this weekend. Will let you know the results.
Thanx, Ford 69
I have a vaccum guage and am looking for the specs on the pump. I'm currently getting about 7 in/hg. What I need to know is, while this amount is adequate to keep the low vaccum indicator off, is it adequate for optimal brake operation.
Also how do I troubleshoot a vaccum pump or brake booster problem besides replacing them and noting the results.
One other development, last week I developed a leak in one of the power steering hoses. Probably the return hose. While troubleshooting the problem I noticed a hissing sound coming from the brake booster. I think it may be a stuck check valve. As such I'll probably replace the brake booster this weekend. Will let you know the results.
Thanx, Ford 69
New User
Joined: Feb 2001
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Vaccum Pump suction
I figured it out. I hooked the vaccum gauge to the hose going into the low vaccum indicator. Started the trauck and got 7 in hg of vaccum. I then disconnected the vaccum hose from the brake booster and plugged the end of the hose. Then the gauge read 20 in hg. To make a long story short, the brake booster is shot. It should not leak air when not being used. I my case it leaks so bad that the vaccum is dropping to 7 in hg.
Thanx, K
Thanx, K
More Turbo
Joined: Nov 2000
Posts: 715
Likes: 11
From: Erie, PA
Vaccum Pump suction
Let me know after you replace it and also if the brakes are stonger. You might be able to lock up the wheels with the new booster.
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Posting Guru
Joined: Nov 2000
Posts: 1,475
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Vaccum Pump suction
Hi, mine does the same thing and everything has been changed rotors drums vac.pump booster master cyl.shoes pads it will stop good but I cant lock the wheels with a jack on the pedal!!!
John
1986 F250 sc xlt lariat 4x4
John
1986 F250 sc xlt lariat 4x4
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New User
Joined: Feb 2001
Posts: 5
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Vaccum Pump suction
Weel finally located and installed the brake booster today. Picked up one at Pepboys but found out it was the wrong one. The master cylinder didn't fit. I think I've had it with them. They never seem to have what I need. Anyway, picked one up today and stuffed it in. Checked the vaccum at idle, it is up from 7 in hg to 22 in hg and the brakes work great!! Thanx, K
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