GMC 12612839 Sprocket Asm,Timing Chain Idler (LH)

Setting and particularly re-timing of the timing system is a delicate process which might lead to rather severe damages of the car engine if something goes wrong, therefore this kind of repair should be attempted only by persons with fairly vast experience in such cases; as for the rest, it is highly recommendable to consult an expert. Firstly, pull the cable off the negative terminal of the battery as well as the spark plugs. Then you need to turn the valve cover, and then to pull it off, next, you need to drain the engine oil, and then the drivebelt and its tensioner, and at last the engine front cover must be removed. Turn the engine clockwise until the No. 1 piston is at the top of the exhaust stroke; align the keyway and markings on the camshaft sprockets. While turning your camshaft removed the timing chain tensioner, and the upper timing chain guide with the help of the exhaust camshaft sprocket bolt. Go forth and, eradicating the adjustable and fixed timing chain guides and then the intake camshaft sprocket bolt. Upon departure of the timing chain, do not rotate either of the camshafts or the crankshaft to prevent damaging the engine. , clean and check the condition of the chain tensioner, timing chain guides and sprockets and replace any that look suspicious. As described above, it is recommended that the experience driver should turn the crankshaft with his hand before starting the engine to feel some specific level of resistance to access the presence of some problems. Upon fitting of the timing chain, ensure that the given timing mark on the crank sprocket is in line and slot the intake camshaft sprocket and bolt it using a new bolt and tighten loosely. Place the timing chain in correct relative position of the colored links to the camshaft sprockets, then bolt in the adjustable and fixed timing chain tensioners, also the upper timing chain cover. The camshaft bolts should be tightly fastened with the camshafts held from turning which will provide enough looseness for installing the timing chain tensioner, which is in compressed position, and making sure that the tensioner assembly in well set. Replace the timing chain oiling nozzle and covering provide sealant on the access plug and replace the valvecove and engine front cover. Reverse all the steps you employed when carrying out the removal process, replace the oil filter, refill the crankcase with oil, reconnect the battery and start the engine and check for oil leaks.

Caution! This is a complex process with an possibility of causing serious engine damage if not done correctly. Without significant experience in this kind of repair, do not try to replace the timing chain; unless you are sure about it, consult a specialist. Before attempting to start the engine, ensure accuracy through double-checking all work. Make sure that all sprockets have timing marks before removing the timing chain(s) from their sprockets. These tools required for this procedure (EN 48383-1, 48383-2, and EN 48383-3) can be obtained from SPX Tools. The following steps outlined below must assume that we have already got rid of the engine, subframe and transaxle assembly,Begin by disconnecting the battery ground cable negative terminal, drain oil out of the car and remove oil filter. Remove spark plugs for easier engine rotation; drivebelt and tensioner; intake manifold; valve covers; water pump; power steering components without disconnecting lines; alternator; crankshaft pulley; Camshaft Position (CMP) sensors; camshaft position actuator valves; engine mount bracket; drivebelt idler pulley thermostat housing. Disconnect each corner bolt with a bolt close to the water pump to release cover from block at bottom end of engine cover and carefully separate from block tapping gently with soft mallet. Turn the crankshaft till primary timing chain sprocket mark aligns with oil pump housing mark at five o'clock position. Engage special tools onto camshafts remove rear cylinder head timing chain tensioner bolts and cautiously take off tensioner. Release special holding tools off cams (camshafts). Repeat this process for lower or primary timing chain on front cylinder head. Clean components replacing as necessary and reset tensioners. Installation with crankshaft sprocket aligned with woodruff key ensuring timing marks are aligned as well as special tools on the camshafts. Mount timing chains, guides and tensioners ensuring accurate positioning of all timing marks, remove camshaft retaining tools. Rotate crankshaft till sprocket mark align with oil pump housing mark at 9 o'clock position; use special locking tools to lock up the cams (camshafts) and proceed to install the rear cylinder head timing chain. Insert inner and outer guides, a new tensioner gasket as well as the tensioner itself. Repeat this process for front cylinder head primary timing chain. Clean timing chain cover carefully, apply RTV sealant then slide over crankshaft using aligning studs before tightening cover bolts. Reinstall everything in reverse but only check proper engine rotation before starting it.

Caution! This is a complex process with an possibility of causing serious engine damage if not done correctly. Without significant experience in this kind of repair, do not try to replace the timing chain; unless you are sure about it, consult a specialist. Before attempting to start the engine, ensure accuracy through double-checking all work. Make sure that all sprockets have timing marks before removing the timing chain(s) from their sprockets. These tools required for this procedure (EN 48383-1, 48383-2, and EN 48383-3) can be obtained from SPX Tools. The following steps outlined below must assume that we have already got rid of the engine, subframe and transaxle assembly,Begin by disconnecting the battery ground cable negative terminal, drain oil out of the car and remove oil filter. Remove spark plugs for easier engine rotation; drivebelt and tensioner; intake manifold; valve covers; water pump; power steering components without disconnecting lines; alternator; crankshaft pulley; Camshaft Position (CMP) sensors; camshaft position actuator valves; engine mount bracket; drivebelt idler pulley thermostat housing. Disconnect each corner bolt with a bolt close to the water pump to release cover from block at bottom end of engine cover and carefully separate from block tapping gently with soft mallet. Turn the crankshaft till primary timing chain sprocket mark aligns with oil pump housing mark at five o'clock position. Engage special tools onto camshafts remove rear cylinder head timing chain tensioner bolts and cautiously take off tensioner. Release special holding tools off cams (camshafts). Repeat this process for lower or primary timing chain on front cylinder head. Clean components replacing as necessary and reset tensioners. Installation with crankshaft sprocket aligned with woodruff key ensuring timing marks are aligned as well as special tools on the camshafts. Mount timing chains, guides and tensioners ensuring accurate positioning of all timing marks, remove camshaft retaining tools. Rotate crankshaft till sprocket mark align with oil pump housing mark at 9 o'clock position; use special locking tools to lock up the cams (camshafts) and proceed to install the rear cylinder head timing chain. Insert inner and outer guides, a new tensioner gasket as well as the tensioner itself. Repeat this process for front cylinder head primary timing chain. Clean timing chain cover carefully, apply RTV sealant then slide over crankshaft using aligning studs before tightening cover bolts. Reinstall everything in reverse but only check proper engine rotation before starting it.

To start with removing the engine parts let the cable of the battery's negative terminal be pulled out, and then the hood. Remove the coolant and the engine oil in addition to unbolting the drivebelt ad the drivebelt tensioner. Subsequently, pull out the thermostat along with the water pump pulley, and then the crankshaft pulley. Bolt the engine support fixture to the engine lifting eyes and remove the passenger side engine mount and the mount support bracket from the front of the timing chain cover. Take out the oil pan, disconnect the coolant from the coolant bypass pipe for some of the engine models, and remove crankshaft position sensor and camshaft actuator solenoid. Withdraw the timing chain cover-to-engine block bolts and, if needed, tap it gently, to take it away from the engine. Mentally place the crankshaft pulley bolt for sometime and rotate the crankshaft until the groove on the crank shaft sprocket is inline with the mark on the chain tensioner plate. Take out the camshaft sprocket bolts while not rotating the camshaft Most of the camshaft sprocket bolts require the use of a special TORX PLUS socket on certain models. Gently unscrew the camshaft sprocket and remove the timing chain and the camshaft sprocket from the engine carefully from the camshaft dowel pin. Check on the timing chain for any signs of wear and damage and it is best to replace the timing chain and sprockets as 'a set'. For particular engines, check the condition of the timing chain tensioner plate and the part within, in order to work properly. Replace the timing case cover gasket, check the condition of the timing chain and sprockets for any sign of wear. To install: remove gasket materials on the cover and engine block put the tensioner plate in place and align the cam shaft before fitting the timing chain to the sprockets. Fasten the camshaft sprocket bolt, apply the chain & sprocket cover and thereafter release the tensioner locking pin. Depress the new gasket with sealant and then employ the cover and fasten the screws in criss-cross manner. Reverse the above mentioned removal steps, replace the oil as well as the coolant start the engine and test for any leakage.

Inspect the timing belt for wear or contamination, replacing it if necessary, especially if it has exceeded 60,000 miles.

Rotate the crankshaft to align the primary timing chain sprocket mark with the oil pump housing mark in the 5 o'clock position.

Position the dowel pin at 3 o'clock, mesh the timing chain with the camshaft sprocket, and engage it with the crankshaft sprocket, ensuring the timing marks are aligned.