Buick 12635427 Chain Assembly, Water Pump & Balancer Shaft

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To remove and inspect the balance shaft chain and balance shafts, begin by disconnecting the negative battery terminal and draining the engine oil. Remove the timing chain, timing chain guides, and sprockets, ensuring the engine is at TDC for cylinder number 1. Remove the balance shaft chain tensioner, adjustable balance shaft chain guide, small balance shaft chain guide, and upper balance shaft chain guide. Then, take out the balance shaft drive chain, and if necessary, the balance shafts (note that shaft removal requires the engine to be out of the vehicle, and shaft bushing replacement should be done by an automotive machine shop). Inspect the components for wear or damage and replace any damaged parts. For installation, ensure the crankshaft timing mark is correctly positioned at 6 o'clock. Install the balance shafts into their bores and tighten the retainer bolts. Align the balance shaft sprockets with arrows pointing up and down, respectively, and use drill bits to lock them in place. Install the balance shaft chain, aligning colored links with sprocket marks, and reset the balance shaft chain tensioner. Recheck timing marks, reinstall the timing chain and all removed components, reconnect the battery, replace the oil filter, refill the crankcase with oil, and finally, run the engine while checking for any leaks. Note that shaft removal should only be attempted by those with expertise, as it typically requires the engine to be removed from the vehicle.

This procedure outlines the removal, inspection, and installation steps for the balance shaft chain and balance shafts, with a note emphasizing that removal of the shafts from the engine block is only possible after removing the engine from the vehicle, and that balance shaft bushing replacement requires professional machine shop service. The removal process involves disconnecting the negative battery cable, draining the engine oil, removing the timing chain, guides, and sprockets, and ensuring the engine is at TDC for cylinder number 1. The balance shaft chain tensioner and guides are then removed, followed by the balance shaft drive chain. For those removing the balance shafts (engine removed), the balance shaft retainer bolts are taken out, and the shafts are removed from the engine block, with caution to mark them for proper reassembly. Inspection involves checking various components for damage or wear. During installation, if the crankshaft was rotated, ensuring the number one piston is at TDC is essential. The balance shafts are then installed into the engine block, and the balance shaft retainer bolts are tightened. The alignment of balance shaft sprockets and chain installation are detailed, with colored links and marks on the sprockets used as references. The chain guides are installed, the balance shaft chain tensioner is reset and reinstalled, and timing marks are checked. Finally, the timing chain and all removed components are reinstalled, and the battery is reconnected.