Dayco Nuline Engine Pulleys With the increasing use of serpentine drive belts on late model engines, more Idler and Tensioner Pulleys are being sold than ever before. All engine Pulleys incorporate ball bearings that run at very high revolutions relative to engine speed. Increasing belt load and exposure to dirt or moisture accelerates bearing ... The concentric pulley tensioner adjuster should have new bearings installed on a regular basis. My rule of thumb is every other timing belt change. The stock timing belt must be changed every 18,000 miles to avoid breakage and a really messed up engine. Gaici Automotive Transmission System Co., Ltd was founded in 2004, which is dedicated to the production of automotive belt tensioner. The company was specialized in developing, manufactureing and distributing automatic tensioner, timing belt tensioner, hydraulic tensioner and tensioner pulley.