LOW COOLANT WARNING LIGHT MAY BE CAUSED BY TRAPPED AIR

VEHICLES AFFECTED: 1986-88 Y-CAR

Customer comments about the low coolant light on 1986 through 1988 Corvettes continuously illuminating when there appears to be an adequate amount of coolant, may be caused by air trapped in the cooling system. The following procedure should be used to repair this condition.

If the low coolant light is on continously during all driving conditions, the coolant light module should be checked for proper function. This can be done by disconnecting the wire at the coolant probe and grounding to the chassis. If the light does not go out, check for broken or loose wires, or faulty low coolant module.

Procedure

1. Check coolant level in the recovery bottle. Coolant must be at or slightly above the "Cold" mark when the engine is cold. If the engine is fully warmed up, the coolant level should be at or slightly above the "Hot" mark.

2. Check for blockage in the overflow hose, overflow radiator nipple and overflow bottle nipple.

3. Clean radiator cap. Check for visible signs of coolant leaks and repair as required.

4. For 1986 and 1987 vehicles built prior to the following break points, it may be necessary to replace the low coolant sensor probe and hose clamps on the coolant recovery hose. Check vehicle identification number and service records to determine whether the probe or hose clamps should be replaced Replace only if required.

Low Coolant Sensor Probe 1987 Coupe G5127143 1986 Convertible G5907034 Hose Clamps 1987 H5101986

For vehicles requiring a new probe or hose clamps the following part numbers should be used:

Quantity Part Number Description Required ----------- ----------- -------- 10054615 Low Coolant Sensor Probe 1

22527587 Hose Clamp (screw type 2 aircraft)

5. Start engine with air conditioning control set to "Off". Refill radiator if coolant level is below the fill neck and reinstall radiator cap.

6. Run three (3) thermal cycles of the engine (cold to operating temperature, approximately 200 degrees Fahrenheit, to cold) using the following steps describing one (1) complete thermal cycle:

Step 1 - Idle engine with air conditioning control set to "Off". mode until coolant temperature reaches approximately 200 degrees Fahrenheit.

Step 2 - Increase idle speed to 2000 RPM for approximately two (2) minutes.

Step 3- Turn vehicle off and add coolant to the recovery bottle to the full hot mark.

Step 4 - Allow vehicle to cool down to 150 degrees Fahrenheit or below.

If this procedure does not repair the low coolant light condition, the total cooling system should be checked for insufficient hose clamping or leaks, including checking the crankcase engine oil for traces of coolant which would indicate an internal engine leak of the coolant. Repeat thermal cycle procedure after repairs are completed.

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.