1986 - 1988 Corvette: Service Bulletin: Low Coolant Warning Light

Subject: Low Coolant Warning Light
Number: 88-43
Section:  6B
Date:  Sept., 1987
Models: 1986-88 Corvettes

To: All Chevrolet Dealers

This bulletin cancels and supersedes Dealer Service Bulletin 87-11 (Section 6B) dated Oct., 1986.  All copies of 87-11 should be destroyed.  Additional procedures regarding thermal cycling are provided in this bulletin.

Low coolant light illumination on 1986-88 Corvettes which appear to have an adequate amount of coolant may be caused by air trapped in the coolant system.

If the low coolant light is on continuously during all driving conditions, the coolant light circuit should be checked for proper function.  This can be done by disconnecting the wire at the coolant probe and grounding the wire to the chassis.  If the light does not go out, check for broken or loose wires or a 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. Clean radiator cap.  Check for visible signs of coolant leaks and repair, as required.
3. 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:
   
   

   Part Number	Description	Quantity Required
   10054615	Low Coolant Sensor Probe	1
   22527587	Hose Clamp (screw type aircraft)	2

4. Start engine with air conditioning control set to "Off". Refill radiator if coolant level is below the fill neck and reinstall radiator cap.
   
   NOTE: STEP 5 SHOULD BE PERFORMED AFTER ANY REPAIR WHICH DISTURBS THE EXISTING COOLANT LEVEL IN CORVETTES.
5. Run the engine through three (3) thermal cycles (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.

Use applicable labor operation time and number.

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.

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