School Bus Fleet Magazine Forums
Home | Profile | Register | Active Topics | Members | Search | FAQ
 All Forums
 Professional Garage
 Enter Forum: Professional Garage
 Park brake issue
 New Topic  Reply to Topic
 Printer Friendly
Author Previous Topic Topic Next Topic  

valleybusman
Top Member

USA
815 Posts

Posted - 03/29/2024 :  06:06:22 AM  Show Profile  Send valleybusman an AOL message  Reply with Quote
I have a 2004 Thomas saftyliner rear engine. In our state patrol inspection, they require. The bus to stop within 50 feet at 15 MPH. After the park brake is applied Bus took 56 feet to stop. So it was placed out of service. In the past it was always a broken spring in the air can. We replaced both air cans and didn't change a thing. The trooper thought the brake was coming on to slow. Could this be the valve that releases the air to the brakes? Could it be the park brake hand valve the test is made up with 2 cones. As soon as the front of the bus gets to the first cone at 15 MPH. The driver pulls the brake and bus must not go past the second cone.Sorry so long.

Bluenozer
Top Member

Canada
655 Posts

Posted - 04/02/2024 :  07:38:26 AM  Show Profile  Reply with Quote
could be a bad slack, wore pin holes in the slack itself , s-cam bushings slowing it down

OEM trained in wiring and all engine platforms for over 20 years
Go to Top of Page

CISDbusman
Advanced Member

306 Posts

Posted - 04/18/2024 :  10:00:24 AM  Show Profile  Reply with Quote
quote:
Originally posted by valleybusman

I have a 2004 Thomas saftyliner rear engine. In our state patrol inspection, they require. The bus to stop within 50 feet at 15 MPH. After the park brake is applied Bus took 56 feet to stop. So it was placed out of service. In the past it was always a broken spring in the air can. We replaced both air cans and didn't change a thing. The trooper thought the brake was coming on to slow. Could this be the valve that releases the air to the brakes? Could it be the park brake hand valve the test is made up with 2 cones. As soon as the front of the bus gets to the first cone at 15 MPH. The driver pulls the brake and bus must not go past the second cone.Sorry so long.





Did ya get it figured out? This one interests me. Thanks!!

Edited by - CISDbusman on 04/18/2024 10:01:02 AM
Go to Top of Page

tigger2
Advanced Member

USA
470 Posts

Posted - 04/19/2024 :  11:50:50 AM  Show Profile  Click to see tigger2's MSN Messenger address  Reply with Quote
Make sure all of the pins in the slack adjusters spin freely, with brake applied slack should be 90* to the shaft of the brake chamber, adjust the brakes and only back off 1/4 turn. Make sure there are no kinks in the brake hoses to the parking brake chambers. Double check the operation of the quick release valve for the parking brake. And lastly make sure the driver takes his foot off of the throttle
Go to Top of Page

valleybusman
Top Member

USA
815 Posts

Posted - 04/19/2024 :  2:45:33 PM  Show Profile  Send valleybusman an AOL message  Reply with Quote
Still working on this issue. Right now there are some electrical issues. So maybe next week
Go to Top of Page

valleybusman
Top Member

USA
815 Posts

Posted - 05/07/2024 :  06:59:26 AM  Show Profile  Send valleybusman an AOL message  Reply with Quote
Got rid of the electrical gremlins. We thought maybe the brakes weren't coming on fast enough and replaced the relay valve. Didn't change anything. So, I think maybe somewhere with the shoes and drums. There is still a lot of shoes left and I have had buses with less work fine.Maybe S cam's
Go to Top of Page

Bluenozer
Top Member

Canada
655 Posts

Posted - 05/09/2024 :  08:52:07 AM  Show Profile  Reply with Quote
do the test in gear 2 instead of drive and get help from transmission , I find these brake tests useless ,best case Ontario, has to be dry and sunny , not a real world test , when greasing the s-cam do it while applied then again with brakes off her in NS Canada we go 35kmp then hammer the foot , and then go 20kmp and pull maxi and take readings off a brake meter dry or wet pavement conditions (50% of our fleet operates on dirt roads) but test will no pass if we do it on dirt or snow covered roads again not a real world test , we do brake jobs once a year on every bus as per law

OEM trained in wiring and all engine platforms for over 20 years

Edited by - Bluenozer on 05/09/2024 08:55:52 AM
Go to Top of Page

B0b
Active Member

34 Posts

Posted - 05/14/2024 :  11:11:38 AM  Show Profile  Visit B0b's Homepage  Reply with Quote
How far do your brake cans stroke? Does the air release good and strong and fast when you pop the valve? Do you have one or two air lines feeding the brake cans? as noted the 90 degree angle is critical.
Go to Top of Page
  Previous Topic Topic Next Topic  
 New Topic  Reply to Topic
 Printer Friendly
Jump To:
 


School Bus Fleet Magazine Forums © 2022 School Bus Fleet Magazine Go To Top Of Page
This page was generated in 0.06 seconds. Snitz Forums 2000