Saturday, January 05, 2008

Haldex Brakes-Self Adjusting Slack Adjusters


Haldex Brakes self adjusting slack adjusters are installed at the factory on all Thomas Buses equipped with air brake systems. This allows much better control over brake adjustment especially for a large school bus fleet operation. At the same time there are operating and maintenance procedures that must be followed to get the best performance out of Haldex Self Adjusting Slack Adjusters.

Here Are Some Important Maintenance Steps To Follow:


  • Visual and operational checks must be made at every scheduled PM check
  • Check adjusters and anchor brackets for visual damage
  • Automatic Adjusters should not be operated as manual adjusters
  • Standard chasis grease may be used to lubricate Haldex Slack adjusters
  • Lubricate the Standard 409-10 model every 50,000 miles or 3 mths
  • Lubricate Reduced Maintenance 409-10 once a year
  • No-Lube 429-10 adjusters are sealed and do not require lubrication
  • DO NOT use Moly-disulfide grease as this will effect the operation of the slack adjuster
  • Replace the slack adjuster if the TORQUE is less than 13 ft lbs when backing off the adjuster. You will hear the ratcheting sound while doing this.
  • Haldex Slack Adjusters should be checked for operation between 90-100 p.s.i. in the air brake system reservoir. Anything over 100 p.s.i. starts to measure deflection in the foundation brakes and does not give a true reading
  • To self adjust Haldex Brakes the operator has to make several full brake applications [spring brakes released] preferably with brakes hot and over 90 p.s.i in the air brake reservoir.

    Here is a very good video explaining proper Brake Adjustment on an air brake system. The self adjusting slack adjuster in this video is not a Haldex but the exact same procedure applies. In my experience with a properly adjusted Haldex slack adjuster the push rod travel averages at 1.5 inches of travel. Well below the Department Of Transport maximum allowed brake adjustment specs.

    Self adjusting slack adjusters are now standard equipment on all Thomas Buses and are a real asset for large fleets who must keep up with Department Of Transport Standards especially with air brakes and proper adjustment. I hope this post has informed you on the proper maintenance of Haldex Brakes.

3 comments :

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Anonymous said...

How about a how to on installing auto slacks? A lot and I mean a lot of mechanics install them wrong

Anonymous said...

TO ANONYMOUS, CALL ANY HALDEX SUPPLIER TO GET A GREAT WALL CHART ON THE HOW TOO'S OF AUTO SLACKS...YOU ARE RIGHT ABOUT INSTALLS BUT ONCE YOU LEARN, THEY ARE THE BEST THING SINCE WHITE BREAD..GOOD LUCK