GM 12637744 Chain Assembly, Camshaft Intermediate Drive

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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.

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.

The time is challenging, and significant powertrain damage may result from mistakes, thus the procedure should be handled by experienced personnel; if not sure, professional advice is recommended. Start with the removal of the negative cabled from the battery, and then position the engine to, TDC compression as per cylinder number 1. Siphon out the engine oil and have the drivebelt and its tensioner pulled off, not forgetting removal of the timing chain cover and the valve cover. Take out the timing tensioner, upper timing chain, exhaust camshaft sprocket bolt, and the timing chain guide, adjustable timing guide, fixed timing guide bolts, intake gearbolt, and the chain itself. Visually check and clean all accessible parts and visually and physically check the chain tensioner, timing chain guides, the timing chain and the sprockets for signs of wear or damage replacing any suspect parts. You have to manually turn the crankshaft at least two times before engaging the starter to look for tightness - signs that seize has set in. Check that the number 1 piston is at Top Dead Centre (T.D.C.), engage the camshaft notches and bolt the intake camshaft sprocket in place using a new bolt. Place the timing chain in position with the camshaft sprocket mark aligning to the unique colored link next to the crankshaft sprocket and cover the crankshaft sprocket with the timing chain. Bolt the adjustable timing chain guide; exhaust camshaft sprocket; fixed timing chain guide; and the upper timing chain guide; then tighten all bolts to the prescribed torque. Closely turn clockwise the intake and exhaust camshaft bolts while using the wrench to hold the camshafts. Apply on the installation position of the timing chain tensioner in compressed position with a dimensional of 2.83 inch length. Bolt the timing chain oiling nozzle securely in place, wet the access plug with RTV sealant and, once again, rotate the crankshaft to feel the drag. Last but not the least, fit the valve cover and the timing chain cover and then connect the battery again, put oil in the crankcase, replace the oil filter and then start the engine and check for oil leaks.

Drain the cooling system and engine oil.

Inspect the timing chain cover for damage, clean all components, and check for wear or damage on guides and sprockets. Reset the tensioners and ensure they are maintained in the retracted position.

Remove the right-side cylinder head timing chain guides and the chain, then repeat the process for the left-side cylinder head.

Loosen the camshaft position actuator solenoid valve.

During installation, ensure the crankshaft sprocket is aligned correctly, install the special retaining tool on the camshafts, and carefully install the timing chains, guides, and tensioners, checking alignment marks throughout.

The timing system is complex, and severe engine damage can occur if mistakes are made. Therefore, this procedure should only be attempted by those with significant experience in such repairs. If unsure, consulting an expert is advised.

The timing chain should be replaced if the engine has high mileage, shows visible damage, or if total free play exceeds one inch.

Caution is advised as the timing system is complex, and mistakes can lead to severe engine damage. Only highly experienced individuals should attempt this procedure, and consulting an expert is recommended if there is any uncertainty.

Temporarily install the crankshaft pulley bolt and turn the crankshaft to align the timing marks on the crankshaft and camshaft sprockets.

Install timing chains, guides, and tensioners, making sure all timing marks are correct, and remove camshaft retaining tools.

Complete the installation in reverse order, ensuring proper engine rotation before attempting to start it.

This procedure necessitates two special tools to lock the camshafts in position, specifically part numbers EN 46105-1 and EN 46105-2.

Inspect the timing chain for wear and damage, replacing it if necessary, and always replace the timing chain and sprockets in sets.