# Brake/ABS issues



## MikeRi24 (Dec 21, 2007)

a couple weeks ago I had a brake line go out on my truck. got it fixed, back on the road, no big deal. Ever since then, I've been having some weird things going on. Every once and a while the pedal will feel a little soft under hard braking and the ABS will just barely start to kick in. I have been checking the fluid regularly and its always full, so I don't think I'm leaking anywhere. Also, when I am making a really night turn at a low speed like under 5 mph and braking (pulling into a parking spot, or pulling into my driveway), the ABS goes off. It doesn't do it all the time though, only sometimes. Anyone have any suggestions? the truck is a 2006 Chevy 2500HD 4x4 6.0


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## watatrp (Jan 10, 2001)

Did you bleed the lines after it was fixed?


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## MikeRi24 (Dec 21, 2007)

watatrp;1162031 said:


> Did you bleed the lines after it was fixed?


yes. i bled the whole system since by the time i limped the truck back to the shop, it drained just about the whole supply of fluid.


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## sweetk30 (Sep 3, 2006)

sounds like you have abs stops. there is lots of info on this. 

basicly the rust builds up under the sensor in the front wheel bearing hubs position that the sensor is bolted in. this pushes the sensor up away from the tone ring in the hub and looses reaction sesitivity at around 5mph and slower and trips the abs system. 

also if you have lots of tiny fine metal parts in the rear diff i have seen them cover the end of the sensor and wont read the tone ring in the rear diff. just pull out and wipe off most of the time. 

if you search abs stop or abs stops it should come up on any search engine.


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## MikeRi24 (Dec 21, 2007)

sweetk30;1162270 said:


> sounds like you have abs stops. there is lots of info on this.
> 
> basicly the rust builds up under the sensor in the front wheel bearing hubs position that the sensor is bolted in. this pushes the sensor up away from the tone ring in the hub and looses reaction sesitivity at around 5mph and slower and trips the abs system.
> 
> ...


ok. is that something I have to replace the whole bearing for or can I just clean it and re-adjust it somehow?


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## tuney443 (Jun 25, 2006)

MikeRi24;1162332 said:


> ok. is that something I have to replace the whole bearing for or can I just clean it and re-adjust it somehow?


For the front,take the sensor off,put something in the bore to keep dirt out while you take a new razor blade and scrape the rust off ,sand a little until you get shiny metal showing,put just a little grease on the metal to keep the rust at bay,clean the plastic sensor,reassemble.It is EXTREMELY sensitive to the proper air gap,that old rust lifts the sensor so it won't work correctly.


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## Clint S (Feb 12, 2008)

tuney443;1162456 said:


> For the front,take the sensor off,put something in the bore to keep dirt out while you take a new razor blade and scrape the rust off ,sand a little until you get shiny metal showing,put just a little grease on the metal to keep the rust at bay,clean the plastic sensor,reassemble.It is EXTREMELY sensitive to the proper air gap,that old rust lifts the sensor so it won't work correctly.


That is IF they come out. I have had a few break be careful. This is a VERY VERY common problem with GM trucks. Every GM truck I have owned has done this. They are included in a hub and you can buy some of them from NAPA or such. I got sick of waiting for the time the ABS would kick in when I was coming to a stop light and rear ending someone so I just pull the fuse when it starts and clean them when I get a chance..


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## 06Sierra (Nov 30, 2008)

I had the same problem in my Wife's 04 Yukon. Broke one of the sensors trying to take it out to clean. I didn't even try the other side, I just picked up two new hubs.


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## Woodenshoe (Oct 30, 2010)

Clint S;1162730 said:


> That is IF they come out. I have had a few break be careful. This is a VERY VERY common problem with GM trucks. Every GM truck I have owned has done this. They are included in a hub and you can buy some of them from NAPA or such. I got sick of waiting for the time the ABS would kick in when I was coming to a stop light and rear ending someone so I just pull the fuse when it starts and clean them when I get a chance..


On our 02' pulling the brake maxi-fuse screws up the rest of the brake system as well (shuts down the whole computer). If you disconnect 1 wheel sensor, the abs will disable itself, but the rest of the brake system will still function normally. Reconnect the sensor, and your back to normal.


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## MikeRi24 (Dec 21, 2007)

found this last night. looks like i've got a project for myself! I will check in with the auto parts store I pull part time duty at and see what my cost on 2 new bearings is. Might just be less of a hassle to replace them all together if its cheap enough.
http://ww2.justanswer.com/uploads/PENTICO/2010-02-13_142442_tahoe.pdf


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## stacks04 (Jan 22, 2008)

Also, I have found that the bleeding procedure on these trucks just isnt effective. We have a brake fluid exchange machine here at work and found that the forced bleed procedure it uses is the best. Basically it pressurizes the master and pushes the fluid out each bleeder one by one. It makes a world of difference doing it this way. 

I have also seen some that never really bled until the abs unit was manually bled using a tech 2 scanner.


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## sweetk30 (Sep 3, 2006)

MikeRi24;1162921 said:


> I will check in with the auto parts store I pull part time duty at and see what my cost on 2 new bearings is. Might just be less of a hassle to replace them all together if its cheap enough.
> http://ww2.justanswer.com/uploads/PENTICO/2010-02-13_142442_tahoe.pdf


if you want new then buy good like timken or other name brand. not the china junk.

also find out the tourqe spec for the axle stub center nut and hand tourqe it down.

NEVER NEVER use a impact to run the nut up to the hub and then tourqe. this will mess up the bearing on the inside and shorten it life span. ITS O.K. to remove the nut with a impact gun tho.


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## MikeRi24 (Dec 21, 2007)

yeah not going with the new bearing route. At my cost Timken ones are $190 each so looks like I'll just be cleaning out the old ones.


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## sweetk30 (Sep 3, 2006)

MikeRi24;1163213 said:


> I'll just be cleaning out the old ones.


if cleaning out vary slow and steady wins the race. the sensor is plastic sitting in the steel body of the bearing. when thay rust up bad thay will freeze the sensor and most of the time brake upon removal.

i use to get new sensors from the dealer but is it realy worth it at around 80-95 bucks each .

good luck on the clean up job. :salute:


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## brad96z28 (Aug 21, 2005)

stacks04;1162944 said:


> Also, I have found that the bleeding procedure on these trucks just isnt effective. We have a brake fluid exchange machine here at work and found that the forced bleed procedure it uses is the best. Basically it pressurizes the master and pushes the fluid out each bleeder one by one. It makes a world of difference doing it this way.
> 
> I have also seen some that never really bled until the abs unit was manually bled using a tech 2 scanner.


Ive yet to ever need to use my tech 2 for bleeding, even after doing tons of complete brake line repairs.


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## marylandbigb (Sep 23, 2009)

i have found that if you spray the area around the sensor with some rust penetrant this helps remove the sensor turn it back and forth gently and when it raises spray some more penetrant and let sit for about 10 minutes and then continue i have done many like this with great results


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## MikeRi24 (Dec 21, 2007)

some great tips guys! I am prob going to pick up the sensors just to have on hand for when I am doing the project just in case I need them.


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## 2004chevy2500hd (Dec 19, 2010)

2004 Silverado 2500HD - Had a similar issue - Upon slowing down the brakes would fade and then grab again. Had a friend suggest that we pull the ABS fuse to see if it was the ABS (trying to isolate the issue). After we pulled the fuse - we did some more tests and the problem went away. Took it to a shop and had the front wheel bearing replaced and have not had that issue since. The only problem with this solution is that it is pricey. Local Chevy dealer wanted $1150 for the parts and labor, this guy wanted $650 - using Napa parts. You could probably save another $300 or so - if you have the skill and time to do it yourself. Hope that helps.


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## Mister Plow (Jan 21, 2009)

Is there a bleeder valve on the ABS unit itself? I've seen some with them, but I'm not sure about the Chevy's. Air in the ABS could cause the symptoms you describe.


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## damian (Jan 29, 2009)

be carefull w\aftermarket sensors weve had problems with them. you definately have rust jacking issues with the frt sensor\s. if it is your personal truck and dont care about abs function pull the fuse.we are having issues with a gm 3500 now doing the same thing we already replaced the sensors and cleaned the mounting surfaces now we have to think we have bad aftermarket sensors-not to spec, or too close clearance due to rust cleaning.as a shop if cleaning the sensor mount surface doesnt take care of it,new wheelbearing assys are in order. good luck


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## brad96z28 (Aug 21, 2005)

damian;1168202 said:


> be carefull w\aftermarket sensors weve had problems with them. you definately have rust jacking issues with the frt sensor\s. if it is your personal truck and dont care about abs function pull the fuse.we are having issues with a gm 3500 now doing the same thing we already replaced the sensors and cleaned the mounting surfaces now we have to think we have bad aftermarket sensors-not to spec, or too close clearance due to rust cleaning.as a shop if cleaning the sensor mount surface doesnt take care of it,new wheelbearing assys are in order. good luck


A lab scope will tell u how ur pattern is if u suspect problems with aftermarket sensors.


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## damian (Jan 29, 2009)

we scanned the patterns with a mapping multimeter with no discernable imperfections.the problem must be very small.we havent really put our backs into it yet.


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## sweetk30 (Sep 3, 2006)

if you have a scanner with abs data output you can test drive and watch the 1 drop out below 5mph when the rest will read 5-4-3-0 

when you spot the bad one it will go 6-5-0-0-0

all abs sensors need the same + or - 1 mph


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## 2004chevy2500hd (Dec 19, 2010)

sweetk30 - I wish I would have known what you just said before.... I had to take my truck to a local guy to trouble-shoot/fix. My brakes would fade in and out around 5mph....(slowing down) - new wheel bearings fixed my issue (in my case).


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## sweetk30 (Sep 3, 2006)

when i was workin in the shop for 10 years if we had one come in up here in the rust belt we basicly told them new w/b unit and be done with it.


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## 2004chevy2500hd (Dec 19, 2010)

MikeRi24 - Did you ever get to the root cause of your issue?


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