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Old 04-01-2013, 09:44 AM
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Vacuum Pump? Vacuum Distribution Block?

So here is whats going on. Brakes pedal is hard to press once the truck is started, it returns to normal after 30+ seconds or a short distance of driving. I immediately thought it was the vacuum pump but I replaced it last week for a brand new one before this issue even started. Maybe I got a bad vacuum pump?

My next two guesses are either the brake booster is going bad or the vacuum distribution block is clogged, cracked etc.

Can the vacuum pump be tested and if so what kind of numbers should I be seeing? I took the hose off of it and stuck my finger on it and it seemed fine.

Any thoughts or has this happened to anyone before?
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Old 04-01-2013, 12:06 PM
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Which hose did you take off for the thumb test? The one right off the pump, or the one at the booster?
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Old 04-01-2013, 01:33 PM
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Quote:
Originally Posted by madpogue View Post
Which hose did you take off for the thumb test? The one right off the pump, or the one at the booster?
The one right off the pump to make sure it had some sort of vacuum. How much if any vacuum should I feel off the booster?
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Old 04-01-2013, 01:50 PM
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Vacuum off the booster hose should be just about as strong as off the pump itself. The distribution block shouldn't reduce it any.

Are you testing it during the initial 30 seconds when you have the pedal problem? Is the red BRAKE (!) dashboard warning light on at the time you have the hard pedal?
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Old 04-02-2013, 04:08 AM
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Quote:
Originally Posted by madpogue View Post
Vacuum off the booster hose should be just about as strong as off the pump itself. The distribution block shouldn't reduce it any.

Are you testing it during the initial 30 seconds when you have the pedal problem? Is the red BRAKE (!) dashboard warning light on at the time you have the hard pedal?
Ok I will check the booster when I get back home from the business trip I am on. I appreciate the help.

Yes, I tried checking at the initial 30 second mark but the brakes are hard maybe 70% of the time at start up. No, the dash brake light is not on, however I am not sure how accurate that gauge for low vacuum is anyway.
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Old 04-02-2013, 04:36 AM
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Red light/vacuum test - start the truck up, block the wheels so you can release the parking brake, pull the hose off the vacuum pump. No vacuum in the distribution block, so the light should come on.

Yeah, those things that only happen part of the time are fun to diagnose .
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Old 04-02-2013, 04:38 AM
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Quote:
Originally Posted by madpogue View Post
Red light/vacuum test - start the truck up, block the wheels so you can release the parking brake, pull the hose off the vacuum pump. No vacuum in the distribution block, so the light should come on.

Yeah, those things that only happen part of the time are fun to diagnose .
I will try that as well. Thanks for your help madpogue
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