Journey with Confidence RV GPS App RV Trip Planner RV LIFE Campground Reviews RV Maintenance Take a Speed Test Free 7 Day Trial ×


Reply
 
Thread Tools Display Modes
 
Old 06-24-2020, 02:11 PM   #1
Bus Crazy
 
banman's Avatar
 
Join Date: Aug 2019
Location: Moved to Zealand!
Posts: 1,517
Year: 2002
Coachwork: Thomas
Chassis: Freightliner FS-65
Engine: 7.2L Cat 3126 turbo diesel
Rated Cap: 71 passenger 30,000 gvwr
abs question...

So the last time I started my 2001 Freightliner FS65 Thomas 70pax all hydraulic /electric bus the ABS light stayed on.

I still have good pressure feel on the brake pedal so I'm assuming (dangerous?) like on a similarly equipped car the brakes are still working fine but the ABS feature is NOT functioning -- off-line for whatever reason...

It's probably wiring from sitting in OH's damp weather but...

What is the procedure for reading the ABS trouble codes on a hydraulic equipped bus?

__________________
David

The Murder Bus
banman is offline   Reply With Quote
Old 06-24-2020, 04:23 PM   #2
Bus Geek
 
musigenesis's Avatar
 
Join Date: Jan 2019
Location: Philadelphia
Posts: 6,995
Year: 2003
Coachwork: International
Chassis: CE 300
Engine: DT466e
Rated Cap: 65C-43A
Did you try resetting the ABS unit with a magnet?
__________________
Rusty 87 build thread
musigenesis is offline   Reply With Quote
Old 06-24-2020, 04:47 PM   #3
Bus Geek
 
ol trunt's Avatar
 
Join Date: Apr 2012
Location: So Cal
Posts: 3,227
Year: 1935
Coachwork: Superior
Chassis: Chevy
Engine: 317 ci/tid / Isuzu
Try cleaning the pick up sensors at the wheels/axle.
Jack
ol trunt is offline   Reply With Quote
Old 06-24-2020, 05:20 PM   #4
Bus Crazy
 
banman's Avatar
 
Join Date: Aug 2019
Location: Moved to Zealand!
Posts: 1,517
Year: 2002
Coachwork: Thomas
Chassis: Freightliner FS-65
Engine: 7.2L Cat 3126 turbo diesel
Rated Cap: 71 passenger 30,000 gvwr
Quote:
Originally Posted by musigenesis View Post
Did you try resetting the ABS unit with a magnet?
I don't think my abs works like that -- it does not match the pix I've seen here of units where it does.

Quote:
Originally Posted by ol trunt View Post
Try cleaning the pick up sensors at the wheels/axle.
Jack
A likely source I agree. I confess, I've done nothing yet 'cause I'm not driving the bus enough to care yet.
Still, (with your example of the sensors) it would be nice to know WHICH sensor was acting up -- I don't like throwing darts in the dark till somthin' sticks to the wall...
If diagnostics can pinpoint the problem then I know whether what I do actually corrects the problem.

and I should have said in the first post -- the brake system is a BENDIX all four calipers are the same part (I really like that design!). The ABS (like a car) has an electric back up pump in the event of engine failure. Mechanical boost is hydroboost from the powersteering when the engines running.
__________________
David

The Murder Bus
banman is offline   Reply With Quote
Old 06-24-2020, 05:52 PM   #5
Bus Nut
 
Join Date: May 2019
Location: Lebanon, Indiana
Posts: 911
Year: 2000
Coachwork: Winnebago
Chassis: Ford F53
Engine: Ford Triton V-10
Rated Cap: currently 2
Perhaps it's just because I learned how to drive before all the technology took over but I don't care for most of it and that includes ABS. I have a pretty finely tuned butt-ometer and usually respond to the situation before the tech anyways. If it doesn't otherwise effect operation and you know how to drive the old fashioned way I'd say don't worry about it. Now of course I realize these days they have nanny systems for the nanny systems so it is possible that somewhere down the road something else will detect the continued ABS fault and flag some other CEL or performance derating or whatever.
Sehnsucht is offline   Reply With Quote
Old 06-24-2020, 06:11 PM   #6
Bus Crazy
 
banman's Avatar
 
Join Date: Aug 2019
Location: Moved to Zealand!
Posts: 1,517
Year: 2002
Coachwork: Thomas
Chassis: Freightliner FS-65
Engine: 7.2L Cat 3126 turbo diesel
Rated Cap: 71 passenger 30,000 gvwr
Quote:
Originally Posted by musigenesis View Post
Did you try resetting the ABS unit with a magnet?
Quote:
Originally Posted by Sehnsucht View Post
Perhaps it's just because I learned how to drive before all the technology took over but I don't care for most of it and that includes ABS. I have a pretty finely tuned butt-ometer and usually respond to the situation before the tech anyways. If it doesn't otherwise effect operation and you know how to drive the old fashioned way I'd say don't worry about it. Now of course I realize these days they have nanny systems for the nanny systems so it is possible that somewhere down the road something else will detect the continued ABS fault and flag some other CEL or performance derating or whatever.
He, he, he...
I too learned to drive looong before ABS was a thing... In fact I remember my dad taking me to an empty, icy mall parking lot one sunday afternoon to experience how the ol' '63 Impala wagon with a 427 big block liked to cut loose with a little go-peddle...

If you think your "butt-ometer" can analyse wheel speed / wheel lockup anywhere near as effectively as a proper abs system you are in a deep, deep mis-guided fantasy...

That said I'll agree that currently driving only a few miles in dry weather I don't need my abs working. I won't pretend to have any idea how my bus with worn tires handles in snow if I slam on the brakes...
__________________
David

The Murder Bus
banman is offline   Reply With Quote
Old 06-24-2020, 07:22 PM   #7
Bus Nut
 
Join Date: May 2019
Location: Lebanon, Indiana
Posts: 911
Year: 2000
Coachwork: Winnebago
Chassis: Ford F53
Engine: Ford Triton V-10
Rated Cap: currently 2
Well if you're gonna drive a bus in snow on bald tires then by all means get that ABS fixed!! LOL
Sehnsucht is offline   Reply With Quote
Old 06-24-2020, 09:43 PM   #8
Bus Crazy
 
banman's Avatar
 
Join Date: Aug 2019
Location: Moved to Zealand!
Posts: 1,517
Year: 2002
Coachwork: Thomas
Chassis: Freightliner FS-65
Engine: 7.2L Cat 3126 turbo diesel
Rated Cap: 71 passenger 30,000 gvwr
Quote:
Originally Posted by Sehnsucht View Post
Well if you're gonna drive a bus in snow on bald tires then by all means get that ABS fixed!! LOL
How else will I learn what sliding that rear over-hang feels like?!
__________________
David

The Murder Bus
banman is offline   Reply With Quote
Old 06-24-2020, 11:17 PM   #9
Bus Crazy
 
Join Date: May 2018
Location: topeka kansas
Posts: 1,771
Year: 1954
Coachwork: wayne
Chassis: old f500- new 2005 f-450
Engine: cummins 12 valve
Rated Cap: 20? five rows of 4?
my abs system

If you have bendix/bosch power steering pump assisted brake booster with an electric motor for back up emergency pressure... it is a Hydromax system.

I have a Hydroboost system with ABS... the systems are not interconnected. I have three wheel speed sensors, one at each front wheel and one at the rear differential. cleaning the tone rings and magnetic sensor for the fronts and removing and cleaning the differential speed sensor would be the second step or third step I would do.

1) check or replace fuses related to ABS

2) inspect wires to sensors and control unit for any damage, unplug connectors and inspect for corrosion

repair any deficiencies

3) clean pick up sensors and tone rings.

If you the abs light is on with out moving the bus, I think you problem is not related to speed sensors. If you have, and know how to use an oscilloscope you can tap into the speed sensors and watch the wave form. nice clean sinewaves are what you want to see, if the frequency is off by much or a dirty wave form then you will have problems. I would tap into right at the abs computer connections, that will also give you indications if the wires are okay too. I have seen one case of a gasoline engine ignition system feeding by way of inductance a speed sensor.....

william
magnakansas is offline   Reply With Quote
Old 06-25-2020, 04:52 PM   #10
Bus Crazy
 
banman's Avatar
 
Join Date: Aug 2019
Location: Moved to Zealand!
Posts: 1,517
Year: 2002
Coachwork: Thomas
Chassis: Freightliner FS-65
Engine: 7.2L Cat 3126 turbo diesel
Rated Cap: 71 passenger 30,000 gvwr
Quote:
Originally Posted by magnakansas View Post
If you have bendix/bosch power steering pump assisted brake booster with an electric motor for back up emergency pressure... it is a Hydromax system.

I have a Hydroboost system with ABS... the systems are not interconnected. I have three wheel speed sensors, one at each front wheel and one at the rear differential. cleaning the tone rings and magnetic sensor for the fronts and removing and cleaning the differential speed sensor would be the second step or third step I would do.

1) check or replace fuses related to ABS

2) inspect wires to sensors and control unit for any damage, unplug connectors and inspect for corrosion

repair any deficiencies

3) clean pick up sensors and tone rings.

If you the abs light is on with out moving the bus, I think you problem is not related to speed sensors. If you have, and know how to use an oscilloscope you can tap into the speed sensors and watch the wave form. nice clean sinewaves are what you want to see, if the frequency is off by much or a dirty wave form then you will have problems. I would tap into right at the abs computer connections, that will also give you indications if the wires are okay too. I have seen one case of a gasoline engine ignition system feeding by way of inductance a speed sensor.....

william
Thanks!
I'll search "hydromax and see if that's what my components look like.
I should make clear if my first post wasn't -- the abs light coming on is a recent thing. It came on with all the warning lights on startup sequence and would then go out with all the other warning lights.

But checking the fuses is sooo annoying what with the fuse panel not being labeled and having to find reading glasses... More seriously -- almost everything's on a circuit breaker but if I can identify the abs I can swap-shoot it for a known good one...

As said, all four of my calipers are identical and all 4 have their own speed sensor. Which with a quick look this afternoon I don't see how they come out of the caliper mount. No obvious fastener -- I don't like just pulling on things until I know they're a pressure fit like a roll pin for example...
__________________
David

The Murder Bus
banman is offline   Reply With Quote
Old 06-25-2020, 07:56 PM   #11
Bus Crazy
 
banman's Avatar
 
Join Date: Aug 2019
Location: Moved to Zealand!
Posts: 1,517
Year: 2002
Coachwork: Thomas
Chassis: Freightliner FS-65
Engine: 7.2L Cat 3126 turbo diesel
Rated Cap: 71 passenger 30,000 gvwr
After a better look at the sensor going into the caliper mount I won't try removing it till I find proper instructions -- it may be that the wheels have to come off to access a fastener from the other side...

Anyway pix of the abs distribution block. No led lights on this model.

Click image for larger version

Name:	IMG_1872.jpg
Views:	9
Size:	130.3 KB
ID:	45982 Click image for larger version

Name:	IMG_1874.jpg
Views:	12
Size:	179.2 KB
ID:	45983
__________________
David

The Murder Bus
banman is offline   Reply With Quote
Old 06-26-2020, 02:04 AM   #12
Bus Geek
 
Join Date: Sep 2015
Posts: 3,856
Year: 2002
Coachwork: Thomas Built Bus
Chassis: Freightliner FS65
Engine: Caterpillar 3126E Diesel
Rated Cap: 71 Passenger- 30,000 lbs.
I am going to follow this thread 'cause the ABS on our bus will come on after 10 to 15 minutes of driving. I might learn something. The Freightliner dealer (waaaaaay back in 2016) said it was the tone ring adjustment and they did make it go away for a little while. It may need to be adjusted once again.


Does your light come on as soon as the engine is started, or does it have a delay of a few minutes?
Native is offline   Reply With Quote
Old 06-26-2020, 07:22 AM   #13
Mini-Skoolie
 
Join Date: Jun 2020
Posts: 55
You probably already did this but there are some fuses for the system you will want to check and I know if you have a good scanner you can read the brake codes also.
DixonM is offline   Reply With Quote
Old 06-26-2020, 10:18 AM   #14
Bus Crazy
 
banman's Avatar
 
Join Date: Aug 2019
Location: Moved to Zealand!
Posts: 1,517
Year: 2002
Coachwork: Thomas
Chassis: Freightliner FS-65
Engine: 7.2L Cat 3126 turbo diesel
Rated Cap: 71 passenger 30,000 gvwr
Quote:
Originally Posted by Native View Post
I am going to follow this thread 'cause the ABS on our bus will come on after 10 to 15 minutes of driving. I might learn something. The Freightliner dealer (waaaaaay back in 2016) said it was the tone ring adjustment and they did make it go away for a little while. It may need to be adjusted once again.


Does your light come on as soon as the engine is started, or does it have a delay of a few minutes?
With your air-brakes vs my hydro I don't know if our hubs would have the same tone ring. This is the first time I've seen a sensor install into the caliper mount rather than directly into the axle housing.

The light comes on and stays on -- no delay.
__________________
David

The Murder Bus
banman is offline   Reply With Quote
Old 06-26-2020, 10:25 AM   #15
Bus Crazy
 
banman's Avatar
 
Join Date: Aug 2019
Location: Moved to Zealand!
Posts: 1,517
Year: 2002
Coachwork: Thomas
Chassis: Freightliner FS-65
Engine: 7.2L Cat 3126 turbo diesel
Rated Cap: 71 passenger 30,000 gvwr
Quote:
Originally Posted by DixonM View Post
You probably already did this but there are some fuses for the system you will want to check and I know if you have a good scanner you can read the brake codes also.
Yes, it's the knowledge of "what kind of scanner and how to" that I'm unfamiliar with on the bus.

My Saab for example uses a proprietary GM Tech2 scanner.
You can plug in a regular ODBII but it will only give very general and sometimes wrong information. The Tech2 will read in depth, allow you trigger the injectors independently and on and on...

my original question stands:
What is the procedure for reading the ABS trouble codes on a hydraulic brake equipped bus?
__________________
David

The Murder Bus
banman is offline   Reply With Quote
Old 06-26-2020, 01:43 PM   #16
Bus Geek
 
Join Date: Sep 2015
Posts: 3,856
Year: 2002
Coachwork: Thomas Built Bus
Chassis: Freightliner FS65
Engine: Caterpillar 3126E Diesel
Rated Cap: 71 Passenger- 30,000 lbs.
Quote:
Originally Posted by banman View Post
Yes, it's the knowledge of "what kind of scanner and how to" that I'm unfamiliar with on the bus.

My Saab for example uses a proprietary GM Tech2 scanner.
You can plug in a regular ODBII but it will only give very general and sometimes wrong information. The Tech2 will read in depth, allow you trigger the injectors independently and on and on...

my original question stands:
What is the procedure for reading the ABS trouble codes on a hydraulic brake equipped bus?
Perhaps this Bendix Service Data Bulletin will help:


Bendix SD-13-4863.pdf


I scanned through it and it does have the proceedure for initiating a blink-code diagnostic. I do not know if you have the models indicated in the data sheet, but it may give you something to work with anyway.
Native is offline   Reply With Quote
Old 06-26-2020, 01:59 PM   #17
Mini-Skoolie
 
Join Date: Jun 2020
Posts: 55
I borrowed a snap on scanner from a friend it’s limited but has useful info here is a picture from the brake section
Attached Thumbnails
9FD20E49-BA6D-4A97-887A-9CEEC67C0664.jpg   89590C4E-D181-4F14-951C-CC7FBFC2A634.jpg   364FC69B-8E30-4A63-AEFB-76DB833621A3.jpg  
DixonM is offline   Reply With Quote
Old 06-26-2020, 10:30 PM   #18
Bus Crazy
 
Join Date: May 2018
Location: topeka kansas
Posts: 1,771
Year: 1954
Coachwork: wayne
Chassis: old f500- new 2005 f-450
Engine: cummins 12 valve
Rated Cap: 20? five rows of 4?
Bulb check

Your ABS light is supposed to light up when you turn the key to the “run” position. All those light are so you can confirm the lights work. The engineers call this portion of the start sequence “ the bulb check”. Idiot light don’t do much good if the bulb is not working. Notice I did not say burned out, but said ‘not working ‘.

William
magnakansas is offline   Reply With Quote
Old 06-26-2020, 11:59 PM   #19
Bus Geek
 
Join Date: Sep 2015
Posts: 3,856
Year: 2002
Coachwork: Thomas Built Bus
Chassis: Freightliner FS65
Engine: Caterpillar 3126E Diesel
Rated Cap: 71 Passenger- 30,000 lbs.
In the original post, Banman stated the ABS light comes on and stays on.
Native is offline   Reply With Quote
Old 05-06-2021, 03:32 AM   #20
Skoolie
 
sepudo's Avatar
 
Join Date: Dec 2019
Location: Socal and Vegas
Posts: 178
Year: 2003
Coachwork: Thomas
Chassis: fs65
Engine: 7.2 catapillar 3126
Rated Cap: 41 students
Quote:
Originally Posted by banman View Post

my original question stands:
What is the procedure for reading the ABS trouble codes on a hydraulic brake equipped bus?
you have the same bus as me so it may be the same.

there's a switch (may be unlabeled ) right next to the J plug, round diagnostic port. once the bus is on you switch it and the abs light will blink a 2 digit code. (ex, 4 blinks pause, 3 blinks = 43 = rear passenger side axel)

also side note I recently learned if there is a ABS problem that is an actual problem, it may also trigger your check trans light.
__________________
@drivingdharma
sepudo is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 12:03 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2024, vBulletin Solutions, Inc.