Sc300 Serpentine Belt / Drive Belt Tensioner Pulley Replacement

mark-sc300 · November 7, 2009

Recently my 1993 sc300 began to have a loud belt squeal noise that would go away after the car warmed up. It had a secondary problem, which was a metallic squeal that occurred even after it warmed-up. The metallic squeal would occur at 2500 RPM, except when AC compressor was on it would begin at 3000 rpm.

I tried some belt dressing which helped tremendously, but the squeal came back after a few days. I read one post that suggested spraying water on the belt from a spray bottle, to determine if it was the belt. This worked and actually permanently minimized the belt squeal. Regardless of these two attempts (belt dressing & water), the metallic squeal that occurred after warmed-up remained.

After removing the serpentine belt it was apparent that the drive belt tensioner pulley bearing was bad. So after looking online and making some calls to the auto parts stores I found that you have two options. You can replace the entire tensioner assembly (with pulley) which the aftermarket part can cost between $150 to $200, or replace only the drive belt tensioner pulley, which the aftermarket part can cost between $20 to $25.

I chose the less expensive approach, since my car only has 75,000 miles on it, I figured that replacing the entire unit was unnecessary. (My theory on cars is to replace only what needs to be replaced. This is not always a financial decision, but based on saving time and sanity.) The aftermarket drive belt tensioner pulley is Duralast part #231055 or Dayco part #89055, which both look like the same part.

The after market drive belt tensioner pulley is slightly larger and has a different design which requires you to locate and appropriate washer to use under the main 14mm bolt. The OEM pulley is beveled and accepts the OEM beveled washer. If you use the beveled washer on the aftermarket pulley it will not spin at all. I suggest finding a washer with a similar thickness to the original OEM washer. You may have to drill it out to allow 14mm bolt to fit through. Also there is no torque specification for this bolt, because it’s not a “dealer replaceable” part. I suggest a torque of ~30 ft/lbs. Since you have to turn it in this tightening direction to install the belt, it will almost torque its self. I suggest putting some locktite medium strength threadlocker blue (OEM 242) on the 14mm bolt, because you don’t want this bolt coming loose.

Serpentine Belts – I had a dealer belt Bando part #W1000-87561 which was squealing after 15000 miles. I replaced it with a Goodyear Gatorback part #4060760. I can’t tell you which is a better belt, but time will tell.

The Gatorback seemed slightly smaller than the old Bando OEM belt. This could be because the 15000 miles on the old Bando OEM belt may have stretched it out a bit. But I will warn you that using the aftermarket drive belt tensioner pulley and the Gatorback serpentine drive belt is a difficult (but do-able) combination. The issue is that the Gatorback seems to be slightly smaller, and the aftermarket drive belt tensioner pulley is slightly larger, which makes it challenging to install the belt. Good luck with all your repairs………