How to Check and Replace a Timing Chain in a Pontiac Bonnevilleby Contributor
When the timing chain breaks in a Pontiac Bonneville, it stops pistons from turning. This leaves valves open and prone to being hit by a piston. The best thing to do is to replace the timing chain yourself at the first sign of weakness, such as the engine cranking over faster than usual.
Remove the Primary and Secondary Camshaft Drive Chains
Access the timing chain by first taking off the following camshaft parts: The intermediate drive shaft sprocket bolt, the primary camshaft drive chain tensioner bolts, the drive chain tensioner and guide bolts, the drive chain guide and finally, the drive shaft sprocket, the primary drive chain and the crankshaft sprocket.
Start on the left side of the camshaft, and take out the left secondary tensioner bolts, and the chain tensioner, aiding it to swell as it is removed. Take the chain guide bolt and the sprocket bolts off the camshaft. Use a wrench at the front of the camshaft, preventing rotation of the engine while the sprocket bolts are being loosened.
Raise the secondary drive chain out of the camshaft sprocket teeth and ease the sprockets away from the camshafts. Take off the left secondary drive chain, the drive chain shoe bolt and shoe, the lower left chain guide bolt and drive chain guide.
Move to the right side of the camshaft and remove the position sensor bolt and sensor in order to take off and throw away the sensor O-ring. Pull off the guide access plugs which are located on the cylinder heads and make sure there is an O-ring seal on the access plugs. Repeat Steps 1 through 4 to remove the primary drive camshaft drive chain.
Install the Secondary Camshaft Drive Chain
Install the secondary camshaft drive chain by putting in the secondary camshaft drive chain guide, and installing the drive chain shoe. Put on the drive chain by easing the chain through the right cylinder head and putting the chain on the end of the camshafts, then meandering the drive chain around the outer row of sprocket teeth.
Put on the exhaust camshaft sprockets into the drive chain and install the exhaust camshafts over the camshafts. Utilize a wrench to line up the sprocket notch to the camshaft pint, and make sure the right intake and exhaust camshaft sprocket notches and camshaft pints line up with the cylinder head.
Use tool J 44212 to put on the right cylinder head camshaft and the upper right drive chain guide bolt, tightening the bolts. Take down the right secondary drive chain tensioner with a ratchet as well as the drive chain tensioner shoe and insert a pin into the release lever hole so the right secondary camshaft drive chain tensioner shoe is collapsed with the release lever facing out.
Install the tensioner bolts, make sure the primary and secondary timing components line up, and install the guide chain access plugs, making sure the O-ring seal is on the access plugs and that the access plugs are tightened. Install a new O-ring lubricated with engine oil, put on the position sensor, and tighten the sensor bolt.
Repeat Steps 1 through 3 to install the secondary camshaft drive chain on the left side.
Install the Primary Camshaft Drive Chain
Put the primary camshaft drive chain on the intermediate camshaft sprocket and the intermediate drive shaft sprocket. Line up the timing marks vertically on the drive shaft and crankshaft sprocket and make sure the number one piston is at the top and center.
Use the tool J 39946 to make sure the pin of the crankshaft is at the one o'clock position before installing the primary camshaft drive chain. Assemble the camshaft intermediate drive chain sprocket and the crankshaft sprocket onto the camshaft intermediate drive shaft and crankshaft.
Collapse the primary camshaft drive chain tensioner and vertically line up the timing marks. Place a small dab of sealant GM P/N 123456739 or equivalent at the split line of the lower and upper crankshafts and put the front cover in position on the crankcase.