GM 91173039 Camshaft (On Esn)

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If the valve train is noisy and Lash Adjusters are suspected, the main thing that you have to check is whether the engine oil is at the right level and it will also be worthy to wait for some time after starting the engine, for the Lash Adjusters to cease their noisy behavior then inspect. Hydraulic Lash Adjusters are non-adjustable types and non-repairable as well; a bad one must be changed. Start by having to do away with the valve cover, timing belt cover, timing belt and the camshaft sprocket, before you rotate the crankshaft 60 degrees anti-clockwise but temporarily. Subsequently, they require the distributor and case to be pulled off from the cylinder head. The camshaft is situated in three bearings of which each is fastened by means of two bolts intended for this purpose. Turn the cap bolts in a slow manner to restore the tension of valve springs in order to remove a stuck cap by giving it a tap lightly. Remove the camshaft, then clean it before placing it in a separate location - preferably a clean container. Take out the Lash Adjusters, wash each of them and mark the Lash Adjusters for easy identification. The Lash Adjusters should be visually inspected for wear and for seizures and the lobe contact surface and the bore surfaces also. These should be replaced if aluminium from the cylinder head is present on them. Take measurements inside the length of the Lash Adjuster bores and note them down and take the outside diameter of the Lash Adjusters. Conduct mathematical computations on the clearance by subtracting the Lash Adjuster diameter with the bore diameter then check the results with specifications, replacing any part if necessary. Clean the top of the bearing caps and the camshaft journals, then put the camshaft in the head without oil and put Plastigage on each journal, and last put the bearing caps back on the head. Loosen the bolt in a cranking manner until you get ready to remove the caps, then check against the crusher Plastigage scale provided. If clearance is higher than prescribed, change the camshaft or the cylinder head. Check for inefficient lubrication, or any problems with the oil before moving to replace the parts. Once the engine is reassembled, the car should be left to stand idle for not less than 30 minutes before starting it to allow Lash Adjusters to seat. Thoroughly clean all parts, apply a fine film of grease to the Lash Adjusters and bores and oil the camshaft bearing surfaces. Fitting a new oil seal to the camshaft and then lowering it before sufficient lubrication has been provided will cause stresses on the part during start up. Put an adhesive to the bearing cap contact surfaces and lubricate the bearing surfaces. Loosening up the bearing cap bolts and then tightening it with increasing intensity then tighten it based on the recommended torque pattern. Reset the other items which we did earlier are camshaft sprocket, timing belt and other parts of timing belt cover. Lastly, take out the spark plugs and turn the crankshaft in a clockwise manner so as to check the knitting of valves, the timing marks should not be misaligned after two turns and adjust the belt as suggested. Whenever there is a feeling of resistance as the crankshaft rotates then valve timing has to be checked.

If the cam lobe height is below the minimum, the camshaft must be replaced.