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1994 Isuzu Box Truck, Vacuum Issue
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trathson
User
May 4, 2015, 10:27 AM
Post #1 of 4
(3354 views)
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1994 Isuzu Box Truck, Vacuum Issue
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I have a 1994 Isuzu box truck, and the vacuum light has started coming on whenever I let off the gas, and the vacuum itself quits working after the first second or two of when the brakes are applied. Resulting in the driver having to ram their foot into the brake pedal to keep the truck stopped.
If the truck is switched to neutral, the problem goes away entirely and the brakes function perfectly with no vacuum light alarm.
Does this sound like the vacuum pump to you guys, or not really?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 4, 2015, 1:40 PM
Post #2 of 4
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Re: 1994 Isuzu Box Truck, Vacuum Issue
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? A "box" truck? Tell me/us, does this have a belt driven vacuum source or use intake manifold vacuum? IDK which.
Duh - no vacuum for vacuum boosted brakes means little braking help no matter how vacuum is had for the booster or booster itself?
T
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trathson
User
May 5, 2015, 6:46 AM
Post #3 of 4
(3318 views)
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Re: 1994 Isuzu Box Truck, Vacuum Issue
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Ok, please forgive my ignorance, I'm not a mechanic. I can just fix things if pointed in the right direction.
I'm not sure if its intake or belt, is there a way I can find out? Here are some pictures of the problem in question, would some experienced eyes be able to point out to me the vacuum... manifold? Or whatever it is called.
http://1drv.ms/1ENUbtE
http://1drv.ms/1E4BAHa
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 5, 2015, 7:48 AM
Post #4 of 4
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Re: 1994 Isuzu Box Truck, Vacuum Issue
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OK - Both pics don't show what I was looking for. Only an alternator in one and an idler pulley in another. I'm really looking for what is behind the master cylinder for a booster and just look for a hose on any booster and where it goes.
Some (doubt this vehicle but possible) will use PS pump fluid pressure called "hydro-boost" still again a unit behind master cylinder with they PS hoses going to it.
OK - So you don't know what system it is and can come and go as said. All types could. Low PS fluid would almost always effect PS as well but make sure it's filled properly just anyway.
Others use a vacuum hose to a, well, large Whoopie Cushion like booster behind the master cylinder. That hose must be good right from there to intake (can get oily on some and fail there) or to a vacuum pump I didn't see but could be hiding. Issue would probably be loose belt if it does do it that way.
Vacuum boosted also uses a check valve and rubber grommet at the booster.
Any can fail in assorted ways. If a hose get the right rated hose frequently by the foot.
Pulling the check valve out booster should go "whoosh" meaning it's holding vacuum. Grommet may fail just taking check valve out so have grommet (somewhat universal) at the ready if you try that.
It would be a lot easier to know what system this is to ask you to target the problem area without writing a whole repair manual for all types possible,
T
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