GM Full-Size Trucks 1970-1979 Repair Guide

Engine

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OIL LEVEL CHECK



See Figures 1, 2, 3, 4 and 5



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Fig. Fig. 1: Check the crankcase oil level with the dipstick



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Fig. Fig. 2: Wipe dipstick using a clean, lint free cloth, then reinsert it in order to get the correct level



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Fig. Fig. 3: Withdraw the stick again and read the level while holding it horizontally - the oil should appear between the ADD and FULL marks on the dipstick



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Fig. Fig. 4: Remove the engine oil fill cap from the valve cover or filler tube (as applicable) ...



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Fig. Fig. 5: ... then add the correct type and amount of engine oil using a funnel to prevent a mess

The engine oil should be checked on a regular basis, ideally at each fuel stop. If the truck is used for trailer towing or for heavy duty use, it would be safer to check it more often.

When checking the oil level it is best that the oil be at operating temperature, although checking the level immediately after stopping will give a false reading because all of the oil will not yet have drained back into the crankcase. Be sure that the truck is resting on a level surface, allowing time for the oil to drain back into the crankcase.

  1. Open the hood and locate the dipstick. Remove it from the tube. The oil dipstick is located on the passenger's side of 6 cylinder engines and on the driver's side of V8s.
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  3. Wipe the dipstick with a clean rag.
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  5. Insert the dipstick fully into the tube, and remove it again. Hold the dipstick horizontally and read the oil level. The level should be between the FULL and ADD OIL marks. If the oil level is at or below the ADD OIL mark, oil should be added as necessary. Oil is added through the capped opening on the valve cover(s) on gasoline engines. Diesel engines have a capped oil fill tube at the front of the engine. See Oil and Fuel Recommendations for the proper viscosity oil to use.
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  7. Replace the dipstick and check the level after adding oil. Be careful not to overfill the crankcase. Approximately one quart of oil will raise the level from ADD to FULL.
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OIL AND FILTER CHANGE



See Figures 6, 7, 8, 9 and 10



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Fig. Fig. 6: The oil drain plug is located at the lowest point of the engine oil pan - if you don't have the proper size wrench or socket, an adjustable can be used to carefully carefully loosen it



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Fig. Fig. 7: The best way to loosen the drain plus is to use the proper sized wrench (or socket) ...



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Fig. Fig. 8: ... then quickly withdraw the plug and allow the oil to completely drain into a suitable pan



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Fig. Fig. 9: Use a strap wrench to loosen the oil filter; install the new filter by hand



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Fig. Fig. 10: Before installing a new oil filter, lightly coat the rubber gasket with clean oil

Engine oil should be cha