vacuum brake booster

mexicanjoe

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Is thee one standard sized vacuum brake booster for F-250 with 7.3 idi? I get about one good stop out of my '89 before the pedal starts stiffening. The master cylinder is new so Im think along the line of a new booster....... any ideas from the gallery??? su amigo: mexicanjoe
 

dgr

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Run a vacuum hose into your cab and measure your vacuum whole using the brakes. I would lean towards the vacuum pump not doing it's job.
 

Selahdoor

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Have you checked for vacuum leaks already? If your vacuum reservoir looks anything like mine did, you have zero or almost zero vacuum, no matter what the pump produces.
 

mexicanjoe

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i have 22" of vacuum with the engine running. im thinking a vac *** leak somewhere... It it appears the vacuum booster is OEM from 1989 so theirs that.... I cant a leak but my question is this: should the booster/ vacuum system go to ZERO as soon as the engine is cut off? secondly , how do you check for vacuum leaks? using sudsy water perhaps?
 

arizhntr

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It should hold vacuum for a while, a visual inspection of the lines is about the only way you can check, Unlike a gasser where you can locate a leak with ether. But the good news is there are only a few systems working with vacuum - cruise control, a/c and brake booster. Check the vacuum check valve at the booster - where the line hooks on. They are plastic and are prone to failure.
 

chillman88

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I've also heard of the fitting on the firewall leaking.

Inspect the fitting and grommet on the booster, then isolate the system. Run a clean vacuum line from the pump directly to the booster. That way if it doesn't leak it can't be the booster. Likewise, if it does leak still, it has to be either the pump or the booster.
 

dgr

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If you want to use soapy water you will need to apply low pressure to the vacuum lines
 

Selahdoor

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You could take the line off of the vacuum pump.... Apply pressure instead of vacuum. (I wouldn't go above say ten to 20 pounds of pressure.) Then use soapy water to test all the lines and such.

And you might be wasting your time if you don't locate the reservoir and test it as well..
 

Slicknik

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@mexicanjoe

you say you have 22” at idle but what happens when you press and hold the brake pedal? How much do you loose?

Your booster check valve could be faulty , your booster could also be failing
 

mexicanjoe

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Oledirtypearl 86 and Selahdoor seem to have the answer...Im gonna try both and wee what happens....Can getting a bigger booster improve pedal feel???
 

Cubey

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My RV's booster was bad despite under 100k miles, so they can indeed go bad.
 

Desertfireguy

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Check that coffee can ( Mine is behind the DS headlight on my 92), your manifold, and one way check valves. Cheap replacement. New vacuum lines aren't that expensive either. Think I bought a 25' spool of motorcraft line for not much of anything.
 
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