Astro pump moan sounds while braking
June 17th, 2012, 5:25 AM
#11
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if a sensor was bad it would turn on the ABS light on the instrument cluster. if the hydraulic unit was bad it should still turn on a light on the dash. the sensor couldnt cause it because they are just magnets attached to the wheels.
do you have a shop manual? you have to see what else is powered by that circuit that you pulled the fuse out of.
do you have a shop manual? you have to see what else is powered by that circuit that you pulled the fuse out of.
June 17th, 2012, 10:00 AM
#12
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ABS related for sure
Since its ABS related for sure, I now think I might have been wrong about where I thought the sound was coming from. I thought it was engine compartment, but it is really ABS pulsing the brakes. Rapid brake pulsing by the ABS creates the sound I thought was a moaning sound.
I understand the sensor is not the source of the noise, but could it be the cause? Is it possible that the sensor could be giving bad input to the ABS hydraulic control unit, causing the ABS to activate when it shouldn't?
I'd rather chase something simpler & less expensive like a sensor, if it might be the root problem. How can I be confident it is the HCU, & not the sensor?
I appreciate your continued patience & input, while I soak up this education, thanks.
I understand the sensor is not the source of the noise, but could it be the cause? Is it possible that the sensor could be giving bad input to the ABS hydraulic control unit, causing the ABS to activate when it shouldn't?
I'd rather chase something simpler & less expensive like a sensor, if it might be the root problem. How can I be confident it is the HCU, & not the sensor?
I appreciate your continued patience & input, while I soak up this education, thanks.
at a time from its function ( as to its electric impulse) as you indicated that you remove the fuse so removing one sensor at a time seems possible
Last edited by stevejohnson48; June 17th, 2012 at 10:02 AM. Reason: miss spelled a word
June 17th, 2012, 12:50 PM
#13
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Let me hopefully again clarify my observations: I've never had an ABS lamp lit before I pulled the 60A ABS fuse, so, I've never had a visual warning indication ever that ABS is a problem.
But ABS is activating when it shouldn't: the ABS system brake pulsing (the sound I called a moan) under gentle brake application as motion slows from about 8mph until stopped is not normal behavior.
RacerX: you say if sensors or the hydraulic unit were bad, I'd get an ABS lamp on dash, but I don't. I don't have a shop manual. Do you agree it is ABS related based on my fuse-pull experiment & results of normal-quiet brake behavior or not?
SteveJohnson48: is there a user-accessible location where the 4 ABS sensors individually plug-in to the control unit? Can I safely unplug them one-at-a-time to further isolate it to a particular sensor?
But ABS is activating when it shouldn't: the ABS system brake pulsing (the sound I called a moan) under gentle brake application as motion slows from about 8mph until stopped is not normal behavior.
RacerX: you say if sensors or the hydraulic unit were bad, I'd get an ABS lamp on dash, but I don't. I don't have a shop manual. Do you agree it is ABS related based on my fuse-pull experiment & results of normal-quiet brake behavior or not?
SteveJohnson48: is there a user-accessible location where the 4 ABS sensors individually plug-in to the control unit? Can I safely unplug them one-at-a-time to further isolate it to a particular sensor?
June 17th, 2012, 5:55 PM
#14
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I dont know, open the hood and feel around for something vibrating or moaning. The ABS is under the master cylinder, if it is the problem you should be able to isolate the noise or vibration from there.
check your power steering reservoir also, might be low on fluid and could be churning air.
check your power steering reservoir also, might be low on fluid and could be churning air.
December 16th, 2013, 7:56 PM
#15
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on my 1999 I had a similar problem it was caused by rust under front wheel speed sensors. apparently at low speeds the signal from sensors is to low making the ABS activate.
January 12th, 2014, 11:28 PM
#16
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RKO... good sugestion. I am a brake tech from way back, and yes, you are right on the button. The ABS sensors will not triger a trouble light if there is no trouble. But as they are magnetic, they pick up all the metalic dust from your brake pads and will triger the ABS when the brake is applied. CHECK and clean ALL OF THEM! That means the rear as well. In most of these trucks the rear has only one sensor, and it is in the pumpkin on the rear. Same deal, gently work it out of its mount, clean and replace. If there is a lot of metal on this, you might have a qualified shop chance the gear oil and assess the condition of the gears inside. Good luck!
Enjoy the ride Amigo.
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Enjoy the ride Amigo.
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