GM Full-Size Trucks 1988-1998 Repair Information

Engine

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CAUTION
Prolonged and repeated skin contact with used engine oil, with no effort to remove the oil, may be harmful. Always follow these simple precautions when handling used motor oil:



Avoid prolonged skin contact with used motor oil.
 
Remove oil from skin by washing thoroughly with soap and water or waterless hand cleaner. Do not use gasoline, thinners or other solvents.
 
Avoid prolonged skin contact with oil-soaked clothing.
 

OIL LEVEL CHECK



See Figures 1, 2 and 3

Every time you stop for fuel, check the engine oil as follows:

  1. Park the truck on level ground.
  2.  
  3. When checking the oil level it is best for the engine to be at operating temperature, although checking the oil immediately after a stopping will lead to a false reading. Wait a few minutes after turning off the engine to allow the oil to drain back into the crankcase.
  4.  
  5. Open the hood and locate the dipstick which is on the left side of the engine. Pull the dipstick from its tube, wipe it clean and reinsert it.
  6.  
  7. Pull the dipstick out again and, holding it horizontally, read the oil level. The oil should be between the FULL or OPERATING RANGE and ADD or ADD OIL marks on the dipstick.
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  9. If the oil is below the ADD mark, add oil of the proper viscosity through the capped opening on the top of the cylinder head cover. See the "Oil and Fuel Recommendations" chart in this section for the proper viscosity and rating of oil to use.
  10.  
  11. Reinsert the dipstick and check the oil level again after adding any oil. Be careful not to overfill the crankcase. Approximately one quart of oil will raise the level from the ADD to the FULL . Excess oil will generally be consumed at an accelerated rate.
  12.  



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Fig. Fig. 1: Remove the oil dipstick and check the oil level



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Fig. Fig. 2: Remove the oil filler cap



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Fig. Fig. 3: Using a funnel, add the proper grade and viscosity of oil

OIL AND FILTER CHANGE



See Figures 4, 5, 6 and 7

The oil should be changed every 7500 miles (12,000 km). General Motors recommends changing the oil filter with every other oil change; we suggest that the filter be changed with every oil change. There is approximately 1 quart of dirty oil left remaining in the old oil filter if it is not changed! A few dollars more every year seems a small price to pay for extended engine life-so change the filter every time you change the oil!

The oil drain plug is located on the bottom, rear of the oil pan (bottom of the engine, underneath the truck).

The mileage figures given are the recommended intervals assuming normal driving and conditions. If your truck is being used under dusty, polluted or off-road conditions, change the oil and filter more frequently than specified. The same goes for trucks driven in stop-and-go traffic or only for short distances. Always drain the oil after the engine has been running long enough to bring it to normal operating temperature. Hot oil will flow easier and more contaminants will be removed along with the oil than if it were drained cold. To change the oil and filter:

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. Warm the oil by running the engine for a short period of time or at least until the needle on the temperature gauge rises above the C mark. This will make the oil flow more freely from the oil pan.
  2.  
  3. Park on a level surface, apply the parking brake and block the wheels.
  4.  
  5. Stop the engine. Raise the hood and remove the oil filler cap from the top of the valve cover. This allows the air to enter the engine as the oil drains. Remove the dipstick, wipe it off and set it aside.
  6.  
  7. Position a suitable oil drain pan under the drain plug.
  8.  

All diesel and gasoline engines hold approximately 5-8 quarts of oil (give or take), so choose a drain pan that exceeds this amount to allow for movement of the oil when the pan is pulled from under the vehicle. This will prevent time lost to the cleaning up of messy oil spills.

  1. With the proper size socket or wrench (DO NOT use pliers or vise grips), loosen the drain plug. Back out the drain plug while maintaining a slight upward force on it to keep the oil from running out around it (and your hand). Allow the oil to drain into the drain pan.
  2.  



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Fig. Fig. 4: With the proper size socket, loosen the drain plug



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Fig. Fig. 5: Remove the drain plug while maintaining a slight upward force, to keep the oil from running out prematurely


CAUTION
The engine oil will be hot. Keep your arms, face and hands away from the oil as it is draining.

  1. Remove the drain pan and wipe any excess oil from the area around the hole using a clean rag.
  2.  
  3. Clean the threads of the drain plug and the drain plug gasket to remove any sludge deposits that may have accumulated.
  4.  
  5. Place the drain pan under the oil filter location to prevent spilling any oil from the filter on to the ground.
  6.  
  7. With a filter wrench, loosen the oil filter counterclockwise and back the filter off the filter post the rest of the way by hand. Keep the filter end up so that the oil does not spill out. Tilt the filter into the drain pan to drain the oil.
  8.  
  9. Remove the drain pan from under the vehicle and position it off to the side.
  10.  
  11. With a clean rag, wipe off the filter seating surface to ensure a proper seal. Make sure that the old gasket is not stuck to the seating surface. If it is, remove it and thoroughly clean the seating surface of the old gasket material.
  12.  
  13. Open a container of new oil and smear some of this oil onto the rubber gasket of the new oil filter. Get a feel for where the filter post is and start the filter by hand until the gasket contacts the seat. Turn the filter an additional 3 / 4 turn with your hand.
  14.  



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Fig. Fig. 6: With a filter wrench, loosen the oil filter counterclockwise



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Fig. Fig. 7: Before installing a new oil filter, coat the rubber gasket with clean oil

  1. Install the drain plug and metal gasket. Be sure that the plug is tight enough that the oil does not leak out, but not tight enough to strip the threads. Over time you will develop a sense of what the proper tightness of the drain plug is. If a torque wrench is available, tighten the plug to 18 ft. lbs. (25 Nm).
  2.  

Replace the drain plug gasket at every third or fourth oil change.

  1. Through a suitable plastic or metal funnel, add clean new oil of the proper grade and viscosity through the oil filler on the top of the valve cover. Be sure that the oil level registers near the (full) mark on the dipstick.
  2.  
  3. Install and tighten the oil filler cap.
  4.  
  5. Start the engine and allow it to run for several minutes. Check for leaks at the filter and drain plug. Sometimes leaks will not be revealed until the engine reaches normal operating temperature.
  6.  
  7. Stop the engine and recheck the oil level. Add oil as necessary.
  8.  

When you have finished this job, you will notice that you now possess several quarts of dirty oil. The best thing to do with it is to pour it into plastic jugs, such as milk or anti-freeze containers. Then, find a gas station or service garage which accepts waste oil for recycling and dispose of it there.

 
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