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One abs/brake mystery solved

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Old 12-30-2009, 07:32 AM
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One abs/brake mystery solved

I had the truck in the shop getting another transfer case, and asked them to scan the abs system, since the light was staying on. I had planned to replace the proportioning valve/rear abs unit, since I have an extra, and figured that was my problem. If not, it had to be wheel sensors.
It turns out that I had a vacuum leak. I didn't know that this would affect the abs, but it does, and after fixing the leak, the lights are off, and the brakes are working as they should. So, if you are having abs issues, which it seems that everybody is, be mindful that you need to have vacuum in the equation.
Old 12-30-2009, 10:06 AM
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Yep a vacuum leak on a '94 or '95 turns on the light.
Usually a leak shows up with a vacuum powered accessory not working right before the light comes on.
Was your cruise control working before the leak was fixed?
Old 12-30-2009, 10:37 AM
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No, the cruise hasn't worked for a long time. Long before these problems arose. The CAD worked fine, although now it engages quicker, and the heater worked fine. The vacuum to the booster was fine, also. I haven't taken the time yet to see where the mechanic fixed the vacuum leak, but I do know that it is a different truck now. With new calipers, pads, flex lines, master, booster, wheel cylinders, hardware and pads, and now the abs works, it stops great.
I know that all this has cost a small fortune, but really, doing most of the work myself and doing it over the course of a year really doesn't make it seem like it cost that much. Out of sight, out of mind.
Old 12-31-2009, 03:04 PM
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Wonder of wonders, the cruise works now! The previous owner had looked into fixing it, and was quoted a high price to replace the works. Turns out, it was just a simple vacuum leak. That was the only thing on my truck that didn't function- now everything works.




Originally Posted by infidel
Yep a vacuum leak on a '94 or '95 turns on the light.
Usually a leak shows up with a vacuum powered accessory not working right before the light comes on.
Was your cruise control working before the leak was fixed?
Old 12-31-2009, 07:31 PM
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Just a guess, but that was probably the source of the vacuum leak. The battery juice drips on the cruise module. In time, the vacuum lines rot away and the cruise module will die.
Old 01-29-2010, 03:49 AM
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Might be a dumb question, but how do you test for a vacuum leak?
Old 01-29-2010, 04:19 PM
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The mechanic used a smoke machine. The vacuum leaked pulled the smoke to it.
Old 01-29-2010, 07:11 PM
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Originally Posted by jayjay
Might be a dumb question, but how do you test for a vacuum leak?
Easy way to test if you have a leak but won't tell you where the leak is is to run the engine for awhile, shut down for five minutes then disconnect any vacuum line.
If it doesn't hiss you have a leak.
A system without leaks will hold vacuum for hours if not days.
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