ENGINE OIL DISCOLORATION OIL LEAK DETECTION. GMC Truck Caballero 1986

For 1990-2009 cars

# ENGINE OIL DISCOLORATION OIL LEAK DETECTION

#### MODELS: ALL 1985-86 MODELS

General Motors Corporation engine plants utilize engine oil dye from time to time in various engines as an aid to oil leak detection during the manufacturing process. The dye causes the oil to glow bright yellow when exposed to a "black" light. There are several sources for "black" lights, such as Kent Moore Tool, Snap-On Tool, Mac Tool, etc. Some of the dye material used gives the oil a slight red or green tint, and in some cases has been mistaken by service personnel for automatic trans- mission fluid or engine coolant. If the engine oil was contaminated with engine coolant, the oil would be a gray or "milky white" color. Trans- mission oil would tint the engine oil light pink, however, it would not glow bright yellow when exposed to a "black" light. Dealers should be advised that the dye is in no way detrimental and that the oil should not be changed if this condition exists. If the engine oil is suspected of being contaminated with foreign material, a small sample (1/4 Cup) should be exposed to a "black" light. If the oil sample does not glow bright yellow, it is possible that the oil is contaminated and should be changed to prevent engine damage.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.