Engine - HT4100 Serpentine Drive Belt Service
87cad5Bulletin No. T 87-145
File in Group 6B
Number 16
Corp. Ref. No. 716204
Date Aug. '87
SUBJECT: HT4100 SERPENTINE DRIVE BELT SERVICE
MODELS AFFECTED: 1985-1987 DE VILE AND FLEETWOOD 1986-1987 ELDORADO AND SEVILLE 1987 ALLANTE
Introduction of the serpentine belt accessory drive system on transverse HT4100 engines has presented service technicians with a unique new technology to become familiar with. This Bulletin will clarify and define current service issues.. This Bulletin supplements information previously published in Bulletins T-85-58 and T-87-60.
BELT APPLICATIONS
There are currently two serpentine drive belts available from GMSPO.
1. Belt 1625691. This belt is 2200 mm long and is used on 1985 FWD C-cars before VIN 321327 (108 amp generator - 52 mm black generator pulley). This belt should not be used on later vehicles with the 120 amp generator.
2. Belt 1643049. This belt is 2210 mm long and is used on 1985 FWD C-cars after VIN 321327 (120 amp generator - 57 mm yellow generator pulley), as well as all 1986-1987 C, E, K, and V cars. Likewise, this belt should not be used on early 1985 cars with the 108 amp generator. This belt replaced 1625690 as described in Bulletin T-87-60.
FIGURE 1 - NEW BELT: NO CRACKS OR CHUNKS:
FIGURE 2 -MODERATELY USED BELT: FEWCRACKS; SOME WEAR ON RIBS AND IN GROOVES. REPLACEMENT NOT REQUIRED:
FIGURE 3 -SEVERELY USED BELT:SEVERAL CRACKS PER INCH. SHOULD BE REPLACED BEFORE CHUNKING OCCURS:
FIGURE 4 - FAILED BELT: SEPARATION OF RIB MATERIAL FROM BACKING (CHUNKING). REPLACE BELT IMMEDIATELY:
BELT WEAR
Figures 1 through 4 illustrate various stages of belt wear to aid technicians in belt replacement decisions. Condition of the belt ribs is best judged as the belt is bent back over the water pump pulley as shown.
FIGURE 5 - BELT TENSIONER:
A serpentine belt will stretch over its service life much like a V belt will do. However, unlike V belts, the serpentine drive system incorporates an automatic tensioner/adjuster to absorb belt growth and provide constant belt tension throughout the belts' service life. The belt must be replaced when the tensioner reaches the limit of its travel. Replacement is required when the arrow cast into the tensioner reaches the end of the "operating range" indicator stamped into the tensioner bracket, Figure 5.
For warranty purposes, use Labor Operation J0667 at .2 hours for all models.