I keep getting a low coolent message coming up on my 99 C5 and I'm trying to figure out why. When I look under the hood, I find that the coolent is just at the right level. You can see the coolent in the clear canister and it's at a proper level. I'm assuming that it's probably a sensor which is causing it. Anyone else get this? Is there an easy fix?

PS: The car has 61K miles.

 

I also have a 99 C5 and get that message about once a month or so. Even though the overflow tank is within the full range while cold... I add about a 1/2 quart of distiled water and that seems to make it happy for another month or so.

So I am actually filling it, just above the "cold full" line. I think my sensor is dirty and maybe not reading accurately.


For those that have not checked there collant level. Check it when the engine is cool. The fill marker line is on the front of the tank (you stand at the front bumper passenger side). Some times its hard to see the exact level... a trick (that I do) is to check it in the dark, or a semi dark. Shine a flash light at the tank from the side and the tank lights up like a fish tank... You can perfectly see the fluid level and the level markers on the tank.

 

Thanks for the advice. I'll try that tomm morning.

 

There's a TSB on this issue:

http://corvetteactioncenter.com/kb/q....php?qstId=259

Subject: Engine Low Coolant Light Comes On At Start-Up (Inspect for 2nd Design Radiator Surge Tank and Replace/Reposition)
Source: Chevrolet Dealer Technical Service Bulletin
Number: 99-06-02-016

Models: 1997-1999 Chevrolet Corvette (1997 Models Built Prior to VIN Breakpoint V5104277)

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)

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

Cause: 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:



The vehicle is a 1997 model, built before VIN V5104277, with the old design radiator surge tank.

The radiator surge tank is improperly installed in the vehicle.

The coolant level in the vehicle coolant system is low.

The float in the tank is sticking.

The coolant level switch connector is improperly connected.

Correction:

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.


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.






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).


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.

Parts Information:

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.

P/N
Descrition

10405218
Tank Assembly, Radiator Surge




GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these 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 your GM dealer for information on whether your vehicle may benefit from the information.



© Copyright General Motors Corporation. All Rights Reserved.


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Related Forum: 1997 - 2003 Technical Forum


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1997-1999: Service Bulletin: Engine Low Coolant Light Comes On (Inspect Rad. Surge Tank, Replace/Reposition)
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