I've got a low coolant light coming on about once every other day while driving. Both the radiator and the reservoir are full (after several checks). I've searched the board here and see that it's probably a faulty sensor and I can probably safely ignore it until I can get it replaced.

But could it also be a water pump issue? (IE water pump not filling the radiator fast enough so the sensor gets exposed and sets the indicator?) I'm watching the engine temp and it stays within normal so the water pump is probably fine. I blew out my last Z28 due to a radiator hose leak (The bottom hose blew out at 1am on a highway and I didn't notice anything amiss until it was too late...) so I'm a bit hypersensitive to this!

 

If you never find the coolant low, then it would seem to be the common sensor problem. Check the level in the radiator before you take it out the first time each day. It should be full to the top. At the same time, make sure the level is correct in the remote reservoir.

 

If you have correctly removed all the air from the system, its a totally closed system. When the pump pulls coolant out of the radiator to feed it to the heads, the exact same amount of coolant will be returned to the radiator from the block. There is no way "water pump not filling the radiator fast enough" can happen. There is no place the coolant to go, other than into the engine and back out to the radiator at exctly the same volumetric flow rate. Coolant is not compressible.

The direction of flow described above is for the "reverse cooled" LT1.... you didn't say which of your two cars is having the problem, but it doesn't make any difference, except whether the coolant flow goes to the heads or the block first.

 

Injuneer - Thanks, I thought about that fact after posting. (It's the '97 btw).

I checked it cold this evening and both the radiator and reservoir were full so it's probably the sensor.

 

Sensor failure is common. Pretty easy to swap them out. Shoebox has a great write-up here: http://shbox.com/1/4th_gen_tech2.html#low_coolant_lamp

 

I would add. Sensor failures are VERY common!!!

 

Thanks guys - What's a good way to drain the radiator this small amount to replace the sensor, some type of hand pump/turkey baster thing?

 

There is a drain petcock at the bottom of the radiator, below the level sensor.