Serpentine Belt Ls 400

[spuds1956]

Have 91 LS 400 repalced EVERYTHINGE on front of engine . All pulleys , tensioner ETC were replaced about 18 months ago. Within the last 2 months had to replace serpentine belt two times. The ribs keep coming off on the inside of belt. Everything is lined up and looks good. Does anyone have an idea what may be problem? Also AC is working fine. ANY HELP GREATLY APPRECATED. Don

[spuds1956]

Have 91 LS 400 repalced EVERYTHINGE on front of engine . All pulleys , tensioner ETC were replaced about 18 months ago. Within the last 2 months had to replace serpentine belt two times. The ribs keep coming off on the inside of belt. Everything is lined up and looks good. Does anyone have an idea what may be problem? Also AC is working fine. ANY HELP GREATLY APPRECATED. Don

[steviej]

check the groves on the harmonic balancer. This is the large pulley that is on the end of the crank shaft. This pulley is a usual suspect when it comes to pulley replacement. In addition check the pulleys on the alternator and AC. If the groves have built up dirt and grime the belt will easily walk off. Lastly, check the belt tensioner, just because it is new, doesn't mean it is not faulty.

My 93 Bonneville SSEi used to throw belts all the time due to built up grime. Are the belts Denso or aftermarket. I did find out that even though aftermarket belts are supposed to fit, their lengths may not be up to OEM spec so even with an automatic belt tensioner, they can still walk.

steviej