Loss of power brakes!! Help!!

[Higgy]

First post, hope to learn alot from you guys....

Heres my problem.

Intermittent power brakes, happened while driving. Noticed there is power when brakes are applied while engine is above idle, but when it idles down while driving, no power assist.

Troubleshot with girlfriends dad. Hooked vacuum pump directly to brake booster, (disconnected vacuum manifold from system), and still no power at idle. I feel vacuum from line from pump is on my finger. He suggested that I replace booster, just want to see what you guys think.

I know the pump is creating vacuum, just dont know how much! Is there a spec as to what the pump should produce? Should I test it with some kind of gauge before I go replacing parts?

The booster itself has no visible cracks, holes, or corrosion, thats why her dad suggested replacing booster. Told me the diaphram inside can wear out letting vaccum pass.

I notice that on the pump the round thing, I guess its where the pump gets its air, is greasy. Figure its power steering fluid getting sucked up from the area where the resivoir is. Girls dad said that isnt the problem.

May or may not help, but the cruise has been intermittent sine I bought truck. Sometimes it works, sometimes it dont. Sometimes it even turns off while driving, figured it was a vacuum problem, just never dug into it.

Thanks for any input in advance, I got to fix it this weekend, and dont want to make a handfull of trips to the parts store!

Higgy

[tjc transport]

welcome to FTE.

what year, model truck, and engine are you talking about??

without these things, we are in the dark.

[Higgy]

95 f250 psd.

Two other members pointed to the pump, after I moved it to the 7.3L area.

If you have any input I'd be glad to hear it.

[tjc transport]

i agree with the vacuum pump.

you should have a minimum of around 17 inches of vacuum at all times. any lower than that, and you will loose power brake efficiency, cruise control, and you may even notice the heat/AC will only blow out the defroster vents, no matter where the vent control is set.

[Higgy]

appreciate it man, So that is a total of 3 ford guys pointing to the pump and one GM guy/Diesel mechanic/future father in-law, saying its the booster!

I guess I'll do what i said in the 7.3 area and see if I can test the pump with a gauge before I buy a part.

So the pump should produce about 17 inches at idle?

Another question, is the output of the pump always a certian value? Or, does it fluctuate as the pump spins at different RPM's?

Thanks again.

[tjc transport]

it is a set amount. it may go as high as 22 inches with a new pump, but anything over 17 is good. i have seen some only put out as low as 7 inches and the people were still driving and wondering what is wrong.

[Higgy]

Thanks again,
I'll report back tomorrow or saturday.

[Higgy]

Thanks for pointing to the vacuum pump. I ONLY had to go to 5 different parts stores to find the part, all city driving without power brakes! To top it off, I didn't have the right kind of puller to swap the pulley, so I had to run up to a local shop and get it swapped, no charge, so that was cool. Thanks again!

[tjc transport]

glad to be of help.