OEM 2003 GMC Envoy Timing Chain

2003 GMC Envoy Parts Questions & Experts Answers

• Q: How to replace the timing chain, sprockets, and tensioner on 2003 GMC Envoy?

  A: Using the camshaft holding tool (J44221) set the tool upside down with the number 1 cylinder at top dead center before installing the crankshaft sprocket coupled with the intake camshaft sprocket into the Timing Chain alignment of the dark link with timing marks on the intake camshaft sprocket. First remove the tension on the Timing Chain by pushing the tensioner shoe in and use the tee to maintain the shoe's position while working. Start by taking off the top chain guide bolts followed by the top chain guide before moving to the exhaust camshaft position actuator bolt and actuator then the intake camshaft sprocket bolt with sprocket then the Timing Chain followed by the crankshaft sprocket. Begin by taking out the Timing Chain tensioner shoe bolt and shoe followed by the Timing Chain tensioner guide bolts and guide before removing the Timing Chain tensioner bolts and tensioner. For installation, secure the Timing Chain tensioner with bolts, tightening them to 25 nm (18 ft. Lbs.), then install the Timing Chain tensioner guide and shoe, tightening to 10 nm (89 inch lbs.) and 26 nm (19 ft. Lbs.) respectively. Begin cylinder head access hole plug installation while tightening them to a torque of 5 nm (44 inch lbs.). Align the Timing Chain dark link by positioning the camshaft holding tool (J44221) flat side up at number 1 cylinder top dead center then install the crankshaft sprocket followed by the intake camshaft sprocket to ensure their timing marks match. Lay the Timing Chain into the head opening and attach it to the crankshaft sprocket while making sure that the dark link faces the timing mark. Before finding the appropriate position the camshaft holding tool (J44221) might need removal for hex camshaft rotation while performing alignment. The intake camshaft sprocket should be put into position atop the intake camshaft followed by installation of the washer and bolt. Slip in the exhaust camshaft actuator along the Timing Chain with dark link positioned at the timing mark of the actuator before fitting it onto the exhaust camshaft by rotating it clockwise to finally tighten the bolt. Advancing the camshaft actuator clockwise until it stops will protect the engine from damage. Tighten the exhaust camshaft actuator bolt to 25 nm (18 ft. Lbs.) use the torque angle meter (J36660-A) to reach an additional 135° while performing a final motion. Tighten the intake camshaft sprocket bolt to 20 nm (15 ft. Lbs.) first tighten the bolt with 25 nm (18 ft. Lbs.) torque then apply an additional 100° torque by using the torque angle meter (J36660-A) in the final pass. After removing the tee from the Timing Chain tensioner and the camshaft holding tool (J44221), check that the dark lines on the chain align with the sprocket marks before installing the top chain guide. Secure the top chain guide bolts using threadlock gm p/n 12345496 on the threads and tighten them to 10 nm (89 ft. Lbs.). The maintenance sequence concludes with reinstalling the engine front cover followed by the camshaft cover.