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LINC400

LOW COOLANT LIGHT

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I had my 1994 Regal with 3.8L flushed in January. The low coolant light came on about 2 weeks ago. Since it was close to being due for an oil change, I took it in to my mechanic and asked them to fill it and check for coolant leaks while it was there for an oil change.

He said he found no leaks, and it was only down a little, so he added some. A week later the light came on again. Yesterday I checked it myself, and it was down about 6 ounces (one funnel worth) and then started overflowing. Recovery tank was full as well.

Today the low coolant light is back on again. Is something wrong with this light, or is something else going on?

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Benefits of AACA Membership.

Although I've never seen yours, a low coolant light sensor is easy enough to check. It's usually just a float connected to a switch in the reserve tank. Since you state that the level is lower when the light goes on, it's working. I wouldn't depend on it forever though.

If you're losing coolant and there are no leaks, then you may have a head gasket going down. I'd first have the engine checked with an ultraviolet leak detector (you put dye in the coolant, run the car long enough for the level to go down, then shine an ultraviolet light on the whole engine looking for the dye). If after that you find no leaks, check your spark plugs. If one of them is cleaner than the others you'll have likely found the head gasket section that's just starting to leak.

In either case (head gasket or leak), if this isn't a prize car you want to last for many years you can likely fix the leak semi-permanently with a commercial block sealer. Just be sure to follow the instructions explicitly, especially if it's the type that requires a pure water application followed by drying.

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Ok, thanks. Now that I know where the sensor is, I will look for it. Maybe the reserve tank is a little low, so I'll fill it and see if the light comes on again. I was mainly checking the radiator itself, which wasn't very low.

If that doesn't work, I was afraid it might be the head gasket.

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In the world of General Motors, from what I've seen, the Low Coolant Sensor screws or is clipped into one of the radiator tanks. A non-float continuity-type electrical item. Some of the earlier ones are about the general size of a little finger, screw into a fitting in a radiator tank, and have a two-wire connector. The later ones are larger, square-shaped, and usually gray, with a clip arrangement.

Also, from what I've seen, the only float-type low liquid level sensors for GM cars were in the windshield washer solvent containers.

Regards,

NTX5467

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After a visual check of the radiator tank seals, from my experience with this vintage 3800, ( 4 cars at various times) you have an intake manifold leak. Most likely invisible as it is slow and active in the form of water vapor.

The good news is the gaskets are cheap and reliable plus they are to install. You'll want a inch pound torque wrench because the bolts are small and the torque requirement is equal to only a few foot pounds. It does take a few hours to complete, mainly because you need to disconnect the wiring harness from the sensors and some can be tough to get to. You'll want to be especially careful of removing the wire on the temperature sensor under the throttle body. The last one we did was rusted on so tight we chose to cut and then resplce the wire under the plastic wire loam.

Just keep in mind that these cars are mostly what I like to call Press and Stick cars. I figure the manufacturer builds everything today for the fastest assembly process. Sometimes this does lead to difficult things to detach, but usually it means there are very few hand tools required to put stuff together again.

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Thanks for the replies. For right now, I filled the radiatior and slightly overfilled the reserve tank. If the light starts flickering on and off again, I'll check everything again. (or even if it doesn't in a few weeks).

If it is low, then there is definitely a leak somewhere, and I am hoping it is not the head gasket. I don't see any coolant in the oil. So hopefully this is a good sign.

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