GM Full-Size Trucks 1980-1987 Repair Guide

Engine

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OIL LEVEL CHECK



See Figures 1, 2, 3 and 4

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



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Fig. Fig. 2: The oil level should show between the "AD" and "FULL" marks on the dipstick



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Fig. Fig. 3: One of the valve covers should be equipped with a capped oil filler opening



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Fig. Fig. 4: To help prevent spilling and wasting oil when filling, use a funnel to pour oil in the valve cover opening

OIL AND FILTER CHANGE



See Figures 5, 6, 7, 8, 9, 10 and 11

Engine oil should be changed according to the schedule in the Maintenance Interval Chart. Under the following conditions the oil should be changed more frequently :



Driving in dusty conditions,
 
Continuous trailer pulling or RV use,
 
Extensive or prolonged idling,
 
Extensive short trip operation in freezing temperatures (when the engine is not thoroughly warmed-up),
 
Frequent long runs at high speeds and high ambient temperatures.
 
Stop-and-go service such as delivery trucks, the oil change interval and filter replacement interval should be cut in half. Operation of the engine in severe conditions such as a dust storm may require an immediate oil and filter change.
 

Chevrolet and GMC recommended changing both the oil and filter during the first oil change and the filter every other oil change thereafter. For the small price of an oil filter, it's cheap insurance to replace the filter at every oil change. One of the larger filter manufacturers points out in its advertisements that not changing the filter leaves one quart of dirty oil in the engine. This claim is true and should be kept in mind when changing your oil.

The oil filter on the diesel engines must be changed every oil change.

To change the oil, the truck should be on a level surface, and the engine should be at operating temperature. This is to ensure that the foreign matter will be drained away along with the oil, and not left in the engine to form sludge. You should have available a container that will hold a minimum of 8 quarts of liquid, a wrench to fit the old drain plug, a spout for pouring in new oil, and a rag or two, which you will always need. If the filter is being replaced, you will also need a band wrench or filter wrench to fit the end of the filter.



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Fig. Fig. 5: The oil drain plug is located at the lowest point of the engine oil pan. Use a ratchet and socket or a box wrench to loosen the plug



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Fig. Fig. 6: Loosen the drain plug by hand while using thumb pressure to keep oil from dripping



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Fig. Fig. 7: Quickly withdraw the plug and keep out of the way of the hot oil stream

If the engine is equipped with an oil cooler, this will also have to be drained, using the drain plug. Be sure to add enough oil to fill the cooler in addition to the engine.

  1. Position the truck on a level surface and set the parking brake or block the wheels. Slide a drain pan under the oil drain plug.
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  3. From under the truck, loosen, but do not remove the oil drain plug using a ratchet and socket or a box wrench.
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  5. Carefully unscrew the drain plug by hand while applying thumb pressure to hold the plug back in position. The pressure will prevent oil from oozing past the drain plug until it is fully withdrawn. Keep a rag handy to quickly wipe off any hot oil which may splash on you.
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CAUTION
The engine oil will be HOT. Keep your arms, face and hands clear of the oil as it drains out.

  1. Once the plug is completely loosened, quickly withdraw the plug and move your hand with the rag away from the stream of hot oil. Allow the oil to completely drain into the pan.
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Do not drop the plug into the drain pan.

  1. When all of the oil has drained, clean off the drain plug and put it back into the hole. Make sure the gasket on the plug is in place and in good condition prior to installing it into the oil pan. Tighten the drain plug on a gasoline engine to 20 ft. lbs. If equipped with a diesel engine, tighten the drain plug to 30 ft. lbs.
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  3. Loosen the filter with a band wrench or special oil filter cap wrench. On most Chevrolet engines, especially the V8s, the oil filter is next to the exhaust pipes. Use caution when working near hot exhaust components, since even a passing contact will result in a painful burn.
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CAUTION
On trucks equipped with catalytic converters stay clear of the converter. The outside temperature of a hot catalytic converter can approach 1200 degrees F.



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Fig. Fig. 8: Only use a strap wrench to loosen the old oil filter



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Fig. Fig. 9: Back the oil filter a few turns, then remove your hand as some of the old oil will flow over the sides



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Fig. Fig. 10: Coat the gasket on the new oil filter with a film of clean engine oil



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Fig. Fig. 11: To prevent overtightening, always install the new filter by hand

  1. Cover your hand with a rag, and spin the filter off by hand. Spin the filter and few turns, then remove your hand as some of the oil will flow down the sides. When you unscrew the filter the rest of the way, be careful to keep it vertical as it still contains up to a quart of oil.
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Confirm that the O-ring from the old oil filter was removed with the old oil filter. If still attached to the adapter when the new oil filter and O-ring are installed, an oil leak will occur.

  1. Coat the rubber gasket on a new filter with a light film of clean engine oil. Screw the filter onto the mounting stud and tighten according to the directions on the filter (usually hand tight one turn past the point where the gasket contacts the mounting base). Don't overtighten the filter.
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  3. Refill the engine with the specified amount of clean engine oil.
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  5. Run the engine for several minutes, checking the leaks. Check the level of the oil and add oil, if necessary.
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