MGM Brakes Service Manual
Contents
1. X Dimension The dimension from bottom of actuator to end of push rod Y Dimension The dimension from bottom of actuator to centerline of yoke pin NOTE If the brake chamber being removed cannot be fully released by applying air pressure the other chamber on the same axle must be same model as one being removed may be used for rod measurement provided it is adjusted properly and operating correctly and is retracted to its zero stroke position brake fully released Otherwise consult the vehicle manufacturer for proper rod length For all Installations Procedure to Cut Push Rod on New Replacement Combination Chamber NOTE The new service chamber push rod must be cut to exactly duplicate the original rod plus yoke length after the yoke assembly is reinstalled on the new chamber s push rod Use the same procedure for measuring the rod on the new unit as used on the unit being replaced Refer to Section 4 for rod cutting instructions e Remove hex nuts and washers on mounting bolts of new chamber clean face of mounting bracket and install chamber on bracket with close attention given to positioning chamber air inlet ports for alignment to vehicle air lines Then install one washer and hex nut on each mounting bolt and using a 15 16 inch 24mm hand wrench DO NOT USE AN IMPACT TYPE WRENCH tighten nuts to MGM Brakes recommended 133 155 Lbs Ft 180 210 Nm torque f Reconnect yoke to slack adjus2. inspect for air leaks at air lines and fittings If bubbles appear tighten fittings slightly but not over 25 30 Lbs Ft 34 41 Nm torque i With spring brake still fully charged with full line pressure apply and hold foot brake treadle valve down to charge service brake chamber IMPORTANT At this time remove vise grip pliers Fig 11 from the service chamber push rod so it can return to a normal position in chamber when service brake is released Test for air leaks around circumference of service clampband with soapy water or air leak detection liquid solution If bubbles appear firmly tap circumference of clampband with hammer and retighten clampband nuts until leaks cease Fig 8 MGM Brakes recommends 30 35 Lbs Ft 41 47 Nm torque on clampband hex nuts j On any MGM Brakes MAGNUM Performance Plus model fitted with an external breather tube wipe open end of connector tube clean to be sure no oil is present apply a good quality rubber cement to the tube and reinsert tube into both of the flexible elbows with a minimum of 1 2 inch 13mm engagement Fig 9 If old single piggyback spring brake was not equipped with an external breather tube drill a 1 2 inch 13mm diameter hole 1 inch 25mm from the top lip of the non pressure chamber Fig 15 at a point closest to the centerline between the air inlet ports on the side which will face away from the road surface Fig 7 Remove burrs around the hole and install a new rubbe
3. If bubbles appear firmly tap circumference of clampband with hammer and retighten clampband nuts until leaks cease Fig 8 MGM Brakes recommends 30 35 Lbs Ft 41 47 Nm torque on clampband hex nuts j Exhaust air pressure from service brake chamber and with air pressure still applied to spring brake chamber tighten the release bolt until it is seated against the head insert and torqued to 50 60 Lbs Ft 68 81 Nm This will ensure the parking brake will have full stroke capability and the release bolt threads will seal out contaminants IMPORTANT Be sure external breather tube is securely engaged a minimum of 1 2 inch 13mm into the rubber elbow Fig 9 and glued together with a high quality rubber cement These units must be mounted with the breather tube facing away from the road surface Fig 7 Failure to comply with these installation instructions will void the MGM Brakes Warranty without remedy Figure 9 A WARNING After replacement of any spring brake actuator the push nore rod stroke and actuating alignment MUST be checked to assure correct gt l i installation and foundation brake adjustment It is very important to recognize that no foundation brake adjustments can be made at either the spring brake chamber or at the service brake chamber and that all sy stroke adjustments MUST be made at the slack adjuster according to the specific recommendations of the foundation brake manufacturer or of the vehicle manu
4. G PROCEDURE All retired spring brake actuators should be safely disarmed before they are disposed of to prevent serious personal injury from accidental sudden release of the high energy power spring as much as 3200 lbs 1450 kgs in the spring or parking chamber To disarm the unit remove it from the vehicle following the instructions in Section 3 for combination chambers or Section 5 for single piggyback chambers Be sure to cage the spring IN WARNING NEVER attempt to remove the head which contains the power spring Observe all safety precautions Place the unit in a steel container and use an acetylene torch to cut a hole through the head housing the power spring Cut completely through at least two spring coils The steel container MUST have openings to expose the head where it is to be cut with the acetylene torch and it MUST be strong enough to prevent parts from hurtling out should the unit suddenly separate before it is safely disarmed It is the user s responsibility to ensure the steel container is safe Information concerning a suitable container is available from your MGM Brakes representative Sewing our customers far aver 50 years www MGMBrakes com MGM Brakes A Division of Indian Head Industries Inc 8530 Cliff Cameron Drive Charlotte NC 28269 9786 704 547 7411 800 527 1534 704 547 9367 Fax email mail mgmbrakes com Form 5044 Revised 2 2010 2001 MGM Brakes All Rights Reserved P
5. LLATION INSTRUCTIONS FOR SINGLE PIGGYBACK SPRING BRAKE CHAMBERS The replacement of a single piggyback spring brake chamber can be done without the removal of the entire combination spring brake from the vehicle The procedure can be made easier by locking off the service chamber push rod To do this engage the service brake by applying the driver s foot brake treadle valve and while applied clamp vise grip pliers onto push rod to prevent rod from retracting when air pressure is released Fig 11 a Determine manufacturer of single spring brake chamber to be removed from vehicle and following that manufacturer s instructions exactly manually release the spring brake completely Instructions for MGM Brakes MAGNUM Performance Plus MJ Series single piggyback spring brakes having integral release bolts are given in Section 2 of this manual Service Manuals for all other design series of MGM Brakes single piggyback spring brakes are also available upon request b Remove both air lines from chamber c On any MGM Brakes model fitted with an external breather tube disconnect the tube and elbow from the service chamber housing Fig 12 d Using a 9 16 inch 14mm wrench or socket remove the nuts on service clampband Next while holding the single piggyback chamber securely in place remove clampband Fig 13 then carefully separate and remove the single piggyback chamber from the service chambe
6. MAGNUM Performance Plus SMe MGM Brakes Service Manual Spring Brake Actuators MJ Series 3 00 76mm Long Stroke Revised 2 2010 For S Cam Tamper Resistant MAGNUM Performance Plus Spring Brake Actuators Figure 1 Your MGM Brakes Tamper Resistant MAGNUM Performance Plus spring brake actuators are an important part of your braking system While they do not require scheduled servicing it is good preventive maintenance to make the following routine inspections minimum of every 50 000 miles 80 400 kms while the vehicle is in the shop for regular servicing of other components A WARNING Your MGM Brakes tamper resistant spring brake has been factory sealed for your protection There are no user serviceable parts inside the spring brake chamber If you experience any damage or failure of your spring brake chamber remove either the entire actuator as in Section 3 of this manual or the single piggyback as in Section 5 of this manual See Section 8 of this manual for disposal instructions Never attempt to disassemble the spring brake chamber as serious personal injury could result from accidental sudden release of the high energy spring MAGNUM Performance Plus SECTION 1 RECOMMENDED INSPECTION POINTS Fig 1 A Visually inspect the exterior surfaces of the unit for signs of damage from outside sources corrosion and or rust If any of these are seen or suspected cautiously remove the complete comb
7. be same model as the one being removed provided it is properly adjusted and operating correctly and is retracted to its zero stroke position brake fully released Otherwise consult the vehicle manufacturer for proper rod length d Before marking push rod to be cut on a new unit be sure the power spring is fully caged and the push rod is fully retracted the zero stroke position This may be done with the integral release bolt or by applying 90 100 psi 621 690 kPa air pressure to the spring chamber air inlet port _ e Take measured X dimension from the removed unit and mark push rod of new unit from the bottom of the actuator Bus f Thread yoke jam nut past mark on push rod Align bottom edge of nut kaa with mark g Use a sharp hack saw and cut push rod on the mark Fig 10 h After cutting rod thread jam nut off to clean up cut thread i Thread jam nut back onto the push rod a sufficient length to allow assembly of the yoke j Thread yoke onto the push rod Yoke from removed unit may be reused provided yoke pin hole is not worn Adjust yoke to the same Y dimension as measured from the removed unit k Hold yoke to prevent it from turning and tighten jam nut against yoke to 25 50 Lbs Ft 34 68 Nm torque To INSTALL NEW UNIT on Vehicle Refer to the MGM Brakes Service Manual for the model that is being installed Refer to Section 3 Step a of this manual SECTION 5 REMOVAL AND INSTA
8. chamber If the PUSH ROD is not square make corrections by repositioning the chamber on the mounting bracket and or by shimming the slack adjuster to the right or left on the camshaft H Inspect the YOKE ASSEMBLY being sure the YOKE PIN is installed and locked into place with a COTTER PIN Replace any damaged worn or missing parts MGM Brakes recommends the YOKE JAM NUT be tightened to 25 50 Lbs Ft 34 68 Nm torque Not Shown 1 On units equipped with a DUST BOOT check the BOOT for tears and replace as necessary Not Shown SECTION 2 MANUAL RELEASE PROCEDURE iy Figure 2 a Before releasing brakes chock wheels of vehicle to prevent movement b Turn the integral release bolt counter clockwise using a 3 4 inch 19mm Turn socket wrench Fig 2 until the power spring is fully caged or compressed Counter Clockwise DO NOT USE AN IMPACT WRENCH Full cage position requires approximately 22 23 turns for 3 00 inch 76mm stroke units MAGNUM Performance Plus models have an MGM Brakes patented dual thread release bolt which reduces the travel of the release bolt by a factor of 2 4 In a 3 00 inch 76mm stroke unit for instance the parking spring is fully caged when the release bolt is up approximately 1 3 inches 33mm from the run position Fig 3 A WARNING Do not exceed this length and do not exceed 74 Lbs Ft 100 Nm torque on release bolt at any time or damage may occur which could prevent any further correct manual release of th
9. e spring brake chamber NOTE For easier turning of the release bolt apply 95 125 psi 655 862 kPa air pressure to the air inlet port marked Spring before Step b above After caging completely exhaust air from the spring chamber SECTION 3 REMOVAL AND INSTALLATION INSTRUCTIONS FOR COMBINATION SPRING BRAKE CHAMBERS NOTE Refer to Cam Brake Adjustment Section 7 of this manual before removing the air brake chamber to be replaced to ensure the brake chamber being replaced will be properly installed with correct rod length a Determine the manufacturer of the combination chamber to be removed from the vehicle and following that manufacturer s instructions exactly manually release the spring brake completely Instructions for MGM Brakes MAGNUM Performance Plus model single piggyback spring brakes having internal release bolts are given in Section 2 of this manual Service Manuals for all other design series of MGM Brakes piggyback spring brakes are also available upon request b Remove cotter pin from the yoke pin knock out yoke pin and remove both airlines from the assembly c Using a 15 16 inch 24mm wrench unscrew hex nuts on mounting bolts and cautiously remove the old chamber from the mounting bracket d Procedure to Cut Service Push Rod to Proper Length Improper installation of the new unit could result in malfunctioning brakes or premature failure of the braking system Refer to Sec
10. ent diaphragms BRAKES OFF NOT APPLIED PROPERLY ADJUSTED BRAKES ON APPLIED Angle must always be greater T F i To check brake adjustment apply than 90 due to various Hi 90 100 psi 621 690 kPa air pressure slack adjuster lengths and F a s4 tothe service chamber Consult the installation setups Refer to bo a E r i vE vehicle manufacturer for the correct axle or OEM manufacturer s its 1 4 angle between the slack adjuster manual for recommended Ta g arm and push rod and or the push angle l Hir rod length This is necessary since i different dimensions are required for automatic or manual slacks various slack lengths and different slack adjuster manufacturers Free stroke should be as short as possible with no lining to drum contact IMPROPERLY ADJUSTED BRAKES ON APPLIED Magnum Approx Dia Rated Stroke Maximum CVSA Maximum recommended readjustment stroke has been exceeded Performance phragm O D of Chamber Plus Stroke MGM Brakes Stroke Alert Visible F Inches MM Inches MM Adjusted Inches MM Excessive Stroke Warning See chart on right 2 50 64 for recommended readjustment 2 50 64 stroke 2 50 64 SOURCE MVMA Motor Vehicle Manufacturers Association SECTION 7 CAM BRAKE ADJUSTMENT ALL SPRING BRAKE AND SERVICE BRAKE ACTUATORS NOTE The following procedure is recommended for proper adjustment SECTION 8 RECOMMENDED SPRING BRAKE ACTUATOR DISARMIN
11. facturer 1 2 inch 13mm SECTION 4 PROCEDURE TO CUT THE SERVICE CHAMBER PUSH z _ Minimum ROD TO PROPER LENGTH A WARNING Do not attempt to service or disassemble the spring chamber on any spring brake actuator A large spring in the spring chamber having extreme force could cause serious bodily injury if it were to suddenly be released due to inadvertent removal of the clampband or tamper resistant head IMPORTANT Place chocks under wheels to prevent vehicle movement before removing air brake actuators a Remove WORN or NON FUNCTIONAL UNIT from Vehicle Determine manufacturer and model of unit to be replaced Refer to that manufacturer s service manual for caging and removal instructions b Make sure the spring chamber of the removed actuator is fully released power spring caged and the service brake push rod is fully retracted to zero stroke position i e brake fully released Refer to Section 3 Pg 4 of this manual if old chamber to be replaced is an MGM Brakes MB or MB T model c Measure and record the X and Y dimensions Fig 4 X Dimension The dimension from bottom of actuator to end of push rod Y Dimension The dimension from bottom of actuator to centerline of yoke pin NOTE If for some reason the spring chamber power spring cannot be caged and fully released then the X and Y dimensions will need to be measured from the other actuator on the same axle must
12. ination chamber by following the directions in Section 3 of this manual Per CVSA out of service criteria any non manufactured hole or crack will place the vehicle out of service Check to ensure that the RELEASE BOLT is seated against head insert and tightened to 50 60 Lbs Ft 68 81 Nm torque This ensures the parking brake will have full stroke capability and seals release bolt threads keeping out contaminants Ensure the BREATHER TUBE is securely engaged a minimum of 1 2 inch 13mm into the rubber elbows and glued together with a high quality rubber cement These units must be mounted with the BREATHER TUBE facing away from the road surface Fig 7 Failure to comply with these installation instructions will void the MGM Brakes Warranty without remedy 0 Check to ensure the SERVICE CHAMBER CLAMPBAND is evenly seated and the clampband bolt nuts are torqued to 30 35 Lbs Ft 41 47 Nm Check to ensure the MOUNTING STUD NUTS are tightened to 133 155 Lbs Ft 180 210 Nm torque clockwise and washers are in place between the nut and the bracket Inspect air lines hoses and fittings attached to the chamber Replace any damaged or leaking parts MGM Brakes recommends the fittings be tightened to 25 30 Lbs Ft 34 41 Nm torque into the chamber air inlet ports Inspect the PUSH ROD to be sure it is working free not bent not binding and is square to the chamber bottom within 3 in any direction at any point in the stroke of the
13. r 4 IMPORTANT At this time take the opportunity to inspect all parts in the service chamber especially the diaphragm and return spring and replace any parts which may be damaged or worn Use only genuine MGM Brakes engineered replacement parts e Make sure new single piggyback spring brake chamber is fully released as outlined in Section 2 of this manual Position diaphragm in bottom recess of chamber Fig 14 and with very close attention taken to assure all mating parts are aligned straight and the air inlet ports are positioned to mate with vehicle air supply lines replace service clampband Fig 13 f Reinstall clampband bolts and nuts Alternately tighten each nut in 5 10 Lbs Ft 7 14 Nm torque increments while constantly rechecking mating parts alignment If realignment is required loosen clampband nuts and repeat Step e above Firmly tap around circumference of clampband with hammer to assure full seating of clampband Fig 8 and tighten nuts to 30 35 Lbs Ft 41 47 Nm torque g Apply sealing compound to hose fittings and reinstall both air lines to chamber making sure each is mated to correct air inlet port according to markings made earlier MGM Brakes recommends the fittings be tightened to 25 30 Lbs Ft 34 41 Nm torque into the chamber s air inlet ports h Using vehicle system air charge parking brake with full line pressure minimum 100 psi 690 kPa Using only soapy water NEVER ANY TYPE OF OIL
14. r elbow into the non pressure chamber Wipe open end of connector tube clean to be sure no oil is present and apply a good quality rubber cement to the tube Insert the tube into the flexible elbow with a minimum of 1 2 inch 13mm engagement so 13mm into elbow Fig 9 1 00 25mm IMPORTANT These units must be operated with the breather tube facing away from the road surface Fig 7 and the tube glued securely into the rubber elbows Failure to comply with these installation instructions will void the MGM Brakes Warranty without remedy k Exhaust air pressure from service brake chamber and with air pressure still applied to the spring brake tighten the release bolt until it is seated against the head insert and torque to 35 45 Lbs Ft 47 61 Nm This will ensure the parking brake will have full stroke capability and the release bolt threads will seal out contaminants SECTION 6 REMOVAL AND INSTALLATION INSTRUCTIONS FOR SERVICE BRAKE DIAPHRAGM A WARNING When servicing a 3 inch 76mm Long Stroke model brake be sure to replace with the correct diaphragm Installation of a standard 2 50 inch 64mm stroke diaphragm into a 3 0 inch 76mm Long Stroke chamber will result in short stroking and could result in air leaks and failure of the unit a Follow all instructions given in Section 5 of this manual paying close attention to positioning the new diaphragm at Step e Use only genuine MGM Brakes engineered replacem
15. rinted in U S A
16. ter being sure the correct diameter and length of yoke pin is installed into the correct hole in the slack adjuster Secure yoke pin with a new cotter pin Figure 7 Breather Inspect the push rod to be sure it is working free not bent not binding and is square to the chamber bottom within 3 in any direction at any point in the stroke of the chamber If the push rod is not square make corrections by repositioning the chamber on mounting bracket and or by shimming the slack adjuster on the camshaft as required Apply sealing compound to hose fittings and reinstall both air lines to the chamber making sure each is mated to the correct air inlet port according to markings made earlier MGM Brakes recommends the fittings be Road Surface tightened to 25 30 Lbs Ft 34 41 Nm torque into the chamber s air inlet ports i Using vehicle system air charge spring brake with full line pressure Figure 8 minimum 100 psi 690 kPa Using only soapy water NEVER ANY TYPE OF OIL inspect for air leaks at air lines and fittings If bubbles appear tighten fittings slightly but not over 25 30 Lbs Ft 34 41 Nm torque IMPORTANT If service brake clampband was loosened to reposition air inlet ports in Step e above apply air to spring brake and then apply and hold foot brake treadle valve down to charge service brake chamber Test for air leaks around circumference of service clampband with soapy water or air leak detection liquid solution
17. tion 7 of this manual for proper cam brake adjustment If the old brake chamber was properly installed use the old brake measurement to determine the proper rod length If the brake being removed was not properly installed or has been damaged too greatly to allow measurement the other chamber on the same axle may be used Otherwise consult the vehicle manufacturer for proper rod length Replacing a Double Diaphragm a MAGNUM MG T or a MAGNUM MJ Performance Plus Model Spring Brake with a MAGNUM MJ Performance Plus Model Combination Chamber Make sure the old spring brake is manually released fully as outlined in Step a above and that the service brake push rod is fully retracted to zero stroke or brakes OFF position Then measure and record both of the following X p and Y dimensions in inches or millimeters outward from bottom face of f service brake chamber Fig 4 X Dimension The dimension from bottom of actuator to end of push rod Y Dimension The dimension from bottom of actuator to centerline of yoke pin 2 Figure 5 Replacing a MAGNUM MB MB T MG or MG T Model Spring Brake with a MAGNUM MJ Performance Plus Model Combination Chamber Make sure the old spring brake is fully released with 90 100 psi 621 690 kPa applied to the spring port Measure and record both of the following dimensions in inches or millimeters outward from bottom face of service brake chamber Fig 4
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