vacuume pump test

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Jul 30, 2010 | 10:29 PM

mikecwik

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vacuume pump test

what should i be reading when doing this test. my brake warning light is going on. im guessing i should be reading 17 hg or so. chilton sucks.

92 7.3

Jul 31, 2010 | 12:01 AM

87crewdually

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From: So. Jersey

At sea level you should have 21in hg within 30 seconds at idle. Make sure you have NO leaks. Also the brake fluid resevoir, low vacuum, and parking brake all can make the light come on.

Aug 2, 2010 | 06:10 AM

mikecwik

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it went to 24 hg. i cleaned low vacuum and low fluid connections though they didnt look bad at all. its going to be sitting for a while but i did idle it for a few minutes and the light never came back on. it was only going on when i would sit at a light for a bit so i jumped to the vacuum pump.

thanks for the figures and other info.

Aug 2, 2010 | 06:40 AM

Lazy K

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If the light comes on only when sitting at a light with the brake on then the booster may be bad. Can you hear a hissing sound when you press the brake pedal?

Aug 2, 2010 | 10:39 AM

87crewdually

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From: So. Jersey

Quote:

Originally Posted by Lazy K

If the light comes on only when sitting at a light with the brake on then the booster may be bad. Can you hear a hissing sound when you press the brake pedal?

X2. If your holding your foot on the brake and your losing vacuum enough to make the light come on, there is a leak in the booster. Alot of times the master cylinder will also be bad, leaking brake fluid into the booster resulting in eating up the booster diaphram.

Aug 2, 2010 | 09:44 PM

mikecwik

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the truck stops like i assume it should. like i said i played the sitting at the light at idle for a bit and the light didnt come on. ill check the line to the booster and see if i can spot fluid. im not losing fluid. no hiss at idle. i didnt lose vacuum at idle on my guage, that was when the light did come on when i was on the road.

this is one im not sure on. when i step on the brakes at idle. the pedal holds and then falls. brakes work great, probably wouldnt note a thing had the light not popped on.

the truck will sit a few weeks and ill get back here to let you know what happens.

Aug 2, 2010 | 11:58 PM

damac

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our clunker hisses constantly when i am on the brake pedal, is that bad?

i tried to rip all the cruise control stuff out myself and replaced a bunch of hosing when we first got it home. however i found that i would have to pump the pedal like 8 times before the brake light would come on, and it has not come on during normal driving conditions.