Engine Low Coolant Light Comes On (Inspect Rad. Surge Tank, Replace/Reposition)

This bulletin is being revised to add the 1999 model year and change the part number identification procedure. Please discard Corporate Bulletin Number 83-62-11 (Section 6 -- Engine)

Some customers may comment that the "low coolant" light comes on at start-up.

This condition may be caused due to the low coolant sensor being mounted in the rear of the radiator surge tank. When the vehicle is parked with the front lower than the rear, the coolant settles in the front half of the surge tank and with the switch in the rear of the tank, the switch float may be low enough to trigger the light. The "low coolant" light may come on if:

Caution: With a pressurized cooling system, the coolant temperature in the surge tank can be considerably higher than the boiling point of the solution at atmospheric pressure. Removal of the surge tank cap, while the cooling system is hot and under high pressure, causes the solution to boil instantaneously with explosive force. This will cause the solution to spew out over the engine, fenders, and the person removing the cap. Serious bodily injury may result.

1. For 1997 vehicles built prior to VIN breakpoint V5104277, replace the radiator surge tank and inspect for an out of position wiring harness under the tank. To repair the harness, position the harness downward and secure with a tie strap. To determine if the surge tank is of the first or second design, inspect the low coolant switch cavity in the surge tank. If the surge tank cavity extends 16 mm (5/8 in) below the bottom of the surge tank, the tank is of a second design tank. If the cavity is less than 15 mm (19/32 in) replace the tank with P/N 10405218.



2. For all vehicles, check the level of the tank by viewing the lower mount on the tank. Less than 2 mm (.08 in) (#1) of the mounting slot should be visible above the attaching nut. If the gap is greater than 2 mm (0.08 in), loosen the surge tank and hold in a downward position to achieve less than a 2 mm (0.08 in) gap above the attaching nut. Tighten the bottom nut first, then both top nuts.

Tighten
Tighten the nuts to 10N·m (89 lb in).

3. Verify coolant level in surge tank:

-	If engine coolant is hot, above 83° C (180° F), fill the coolant surge tank 12 mm (½ in) above the cold indicator mark.

-	If the engine coolant is at ambient room temperature, fill to the top of the cold indicator mark.

All parts in the GM Parts System since January 1997, and all parts used to manufacture vehicles since January 1997, are of the second design. If a vehicle is one of the 1997 vehicles prior to the serial number breakpoint, you may have to replace the radiator surge tank as described in Step 1, above.

Parts are currently available from GMSPO.

For vehicles repaired under warranty, use :