Accessory Drive Belt - Broken/Damaged
90ford17^ ACCESSORY DRIVE BELTS-7.3L-BREAK-IMPROPER TENSION-AMBULANCES WITH LEECE NEVILLE ALTERNATOR
^ ACCESSORY DRIVE BELTS-7.3L-WITH LEECE NEVILLE ALTERNATOR AND VACUUM PUMPTIGHTENING PROCEDURE-AMBULANCES
Article No. 90-11-12
LIGHT TRUCK: 1988-90 E-260, E-350, F SUPER DUTY, F-250, F-350
ISSUE: Accessory drive belts that break or become damaged may be caused by mis-adjusted belts. Too much tension can stretch the belt and cause it to break. Not enough tension can cause the belt to slip in the pulleys which will generate excessive heat and damage the belt.
ACTION: Use the following procedure to set the 7.3L diesel engine accessory drive belts to the proper tension.
1. Check the condition of the accessory drive belts. Replace the belts as required. If a seasoned belt has tension in excess of 180 lbs., replacement is recommended. Refer to the 1990 Econoline or F-Series Shop Manual, Section 27-06 for service details.
^ When replacing the alternator belt, use belt (E8US-8620-BA). DO NOT USE A SUBSTITUTE PART.
^ When replacing the vacuum pump belt, use belt (D22E-8620-CA). DO NOT USE A SUBSTITUTE PART.
Figure 1:
2. Remove the bolts at the pivot and adjusting locations of the vacuum pump mounting bracket, Figure 1.
Figure 2:
3. Inspect the vacuum pump mounting bracket under the head of the bolts.
^ If a noticeable groove has been formed on the sides of the slotted hole of the vacuum pump mounting bracket under the head of the bolt, replace it (E3TZ-2C140-B), Figure 2.
^ If the surface of the vacuum pump mounting bracket is OK, go to Step 4.
4. Install two (2) new bolts that have conical washers (N606688-S2) at the pivot and adjusting hole locations of the vacuum pump mounting bracket.
NOTE: THE CONICAL WASHER ON THE BOLT INCREASES THE BEARING SURFACE AND CLAMP LOAD ON THE BRACKET. IT IS NOT NECESSARY TO OVERTIGHTEN" THE BOLTS TO MAKE SURE THEY HOLD.
5. Before setting the tension on the alternator belt, make sure the vacuum pump mounting bracket bolts are loose at the pivot and adjusting hole locations.
CAUTION: TIGHTENING THE ALTERNATOR BELT WHILE THE VACUUM PUMP IS TIGHT MAY SEVERELY OVER-TENSION THE VACUUM PUMP BELT.
6. Be aware that when adjusting the various brackets, the belt tension setting is sensitive to the bolt tightening sequence. In ALL cases, the pivot bolt should be tightened first and the adjusting bolt (the one through the slotted hole) should be tightened last.
The bolt torque specification for tightening the bracket mounting bolts is shown in the following chart.
7. If a new alternator belt is installed, the tension must be reset after five (5) minutes of engine operation. The tension on the new belt will tend to decrease as the belt flexes and "seats" into the pulley.
NOTE: RE-TENSIONING OF THE ALTERNATOR BELT WILL REQUIRE LOOSENING THE VACUUM PUMP BRACKET AND RE-SETTING THE VACUUM PUMP BELT TENSION AFTER THE ALTERNATOR BELT TENSION HAS BEEN RESET.
8. If a new vacuum pump belt is installed, the tension must be reset after five (5) minutes of engine operation. This belt is particularly sensitive to the bolt tightening sequence. Remember to tighten the pivot bolt first and then the adjusting bolt.
9. The Leece-Neville alternator has a built in jack screw for adjustment. Make adjustments as follows:
^ Use hand tools
Figure 3:
^ Use of a tension gauge when setting the tension is required for proper operation of the belts. A standard "V" belt tension gauge (T63L-8620-A), Figure 3, or equivalent is recommended
^ Take tension measurements at midspan
^ Take several measurements, moving up and down the span to avoid a bad measurement which might occur on a seam of the belt material.
^ Take the measurement of a cogged belt at the thick section of the cog not between the cogs.
(*) A seasoned belt is one which has been run for more than five (5) minutes.
OTHER APPLICABLE ARTICLES: None
WARRANTY STATUS: Eligible Under Basic Warranty Coverage
OPERATION DESCRIPTION TIME
901112A Vacuum Pump Inspection - 0.6 Hr.
Replace Bolt & Plate (Econoline)
901112A Vacuum Pump Inspection - 0.4 Hr.
Replace Bolt & Plate (F-Series)
901112B Replace Alternator Belt 0.5 Hr.
(F-Series, Econoline)
DEALER CODING BASIC PART NO. CONDITION CODE
8620 07
OASIS CODES: 4400, 4700, 4800