Supercharged 3800 Coolant Flush/Refill Procedure

[Lesabre T-type Chris]

I recently did a coolant flush on my '99 Regal GS (also changed the hoses and thermostat). Now the "low coolant" light comes on although it will eventuallly go off after driving for a while. I have checked the radiator and coolant tank and they are filled to the proper level. Can anyone help me with this problem?

[NTX5467]

The sensor for the "Low Coolant" is most probably in the radiator tank (probably the passenger side?). About half-way down the tank, or thereabouts.

Have you tried to top off the system after the engine has cooled down, after the initial refill? I suspect that on a "closed" cooling system, the "proper level" in the radiator, when the vehicle is cooled and such, is for the coolant to be actually up inside the filler neck of the radiator, not "below" that level as it might be on an "open" cooling system with no coolant reservoir or surge tank.

What about the level in the coolant reservoir? Is it stable or not? Are there any visible leaks or seeps? Is it overheating too? Some of the later 3800s have been known to have coolant leaks in the intake manifold area (check with your dealer to see if it applies to your vehicle).

Some engine/vehicle combinations have a bleeder valve at the "high point" in the cooling system. This allows the trapped air that might get into the cooling system during flush/refill operations to be purged from the system; works just like a brake fluid bleeder. I don't recall if your engine/vehicle combination ha such a bleeder valve, but it might be worth checking to see if it does. Even if it has a bleeder valve, the hose configuration and component locations on modern fwd vehicles can make it necessary to do several "top offs" after any type of coolant change/service as you have done.

Depending upon the "flush solution" you used, it might have damaged the sensor, which is some sort of continuity circuit, I believe. They are not terribly expensive or hard to change, once you know where they are. Of course, changing one would require draining some coolant from the system so then you'd have to do the refill operation all over again.

Just some thoughts,

NTX5467