GM 12586481 Sprocket, Camshaft

Some of the timing system can be quite difficult to manipulate and it is very easy to cause further damage to the engine if any wrong step is taken, thus it is highly recommended that only those who have considerable experience in such repairs attempt it; in any case, they should consult a professional. Recheck all work and make sure all are right before start the engine. Special tools are required to lock the camshafts on each cylinder head into position, with two designs for the sprockets and chains: The first models, from 2005 to mid-2007, employ Design 1, which involves using camshaft locking tools EN-46105-1 and EN-46105-2, while the later ones, from mid-2007 to 2014, use the tools EN-48383-1, EN-48383-2, and EN-48383-3 and comes with 'inverted tooth' chains for less First, you have to take off the timing chain cover and for models of 2005 and half of 2007, rotate the crankshaft to the position with the mark on the oil pump housing vertical in the nine o'clock position while the flat backlash on the ridge of each camshaft on the right-hand cylinder head faces upwards. Attention should be paid to the installation of the special tools to the camshafts, then unscrew the fixing bolts for the timing chain tensioner for the right-side cylinder head and, having removed it along with the gasket, carefully put it aside. Move on to the removal of the right side cylinder head timing chain guides and the chain then do the same thing on the left side of the cylinder head. If required, one can take off the idler sprockets and locate the position of the camshaft sprockets and the camshaft before taking off the sprocket bolt. As for the mid 2007 and onward models, there is a similar process that must be carried out, but the crankshaft comes to a specific position and proper locking tools used. Check the timing chain cover for damage, scrub all components and look for such signs of wear or damage as on guides and sprockets. Remove tension from the tensioners and make sure that they are to be kept in a compact mode. When positioning of the crankshaft sprocket, woodruff key should be fitted with the timing marks visible and aligned before fitting the timing chains and the guides with the bolts tightened to the stipulated torque. Once more tighten all the timing marks appropriately, briefly turn the crankshaft to check for drag - which will signify a problem - before unlocking the tools.

Verify the alignment of all marks and set the timing belt tension.

Align the crankshaft sprocket with the Woodruff key and slide it onto the crankshaft, ensuring the timing mark is visible and aligned.

Detach the timing chain cover-to-engine block bolts and separate the cover from the engine, using a soft-face hammer if necessary.

Carefully pry the variable camshaft timing sprocket off the camshaft dowel pin and slip the timing chain and camshaft sprocket off the engine.