Radiator Low Level Module Replacement

The low engine coolant warning message lit up on my car.  I checked the level in the bottle and in the radiator itself and both were fine.  So to my trusty service manual I went.

  1. The first step in the service manual says to perform a Engine Cooling Diagnostic System Check.  As I don't have a scan tool, I skipped it.
  2. Turn ON ignition with the engine OFF.  Does the low coolant level message appear?  [Yep]
  3. Test the low coolant level indicator control circuit of the low coolant level indicator for a short to ground.  I did something different, I disconnected the module and repeated step 2.  Since the light went off, I figured it was the module.

The module is located on the passenger side of the radiator, under the fill neck.
There is a lot of stuff in the way.  I took off the headlight assembly to get better access.  You could also remove the battery.  If you can help it, don't.  To remove the battery, you have to take off the radiator support bar and move a lot of cabling around.  Then try and lift the heavy thing around the fender.  Putting it back in is even more trouble.
This is the module.  It slides in and is held in place with a metal spring clip.  Two o-rings provide the seal.
This is what the clip looks like.
  1. Disconnect the negative battery cable.
  2. Disconnect the harness from the module.
  3. Pry up one leg of the clip from its locked position, then the other.
  4. Pull the module rearward with a slight twisting motion.  "Slight" is the word here.  The outer flange of the module mount on the radiator tank is square so you can't twist the module very far.  Don't force it.  You could possibly break off the nipple.
  5. Install the new module.  Because the o-rings are new, it's going to hard to install the module.  Just work slowly and use the slight twisting motion.  Eventually the clips will seat themselves over the barbed tabs.  Reconnect the harness and the battery.
Couple of things to note:
  1. Do I need to say that you should do this ONLY when the engine is cool?
  2. You are supposed to partially drain the radiator.  I figure if I was fast enough, I would lose only a little coolant, so I didn't.  As it turned out, I only lost less than 1/3 gallon.  As long as you have the replacement module ready to go, leave the system filled.  Also leave the radiator cap on, it will slow the drain rate.
  3. If you do drain the radiator, lubricate the o-rings on the module with coolant.
Last step is to refill the radiator.  Use only Dex-Cool, either from GM or Havoline, and water.  You need to open the air bleed vent on the water outlet housing.  You need to remove the engine cover.  On both the 3.4L and 3.8L engine, it is on the driver's side of the car.  For the 3.4L, it looks like a pan head screw (standard flat blade screwdriver).  On the 3.8L, it has a hex head.  On the 3.8L it is made out of brass.  (see photo)  I don't know what it looks like on the 3.4L.  Also on the 3.4L, you need to open the air bleed vent on the thermostat bypass pipe.  A couple of turns is enough.  You can check by squeezing the radiator hose when the radiator cap is on.  You should hear air escaping from the vent.  Fill with coolant through the radiator neck.  After it reaches the base of the neck, wait a few minutes and check the level.  Repeat until the level stabilizes.  Close all the air bleed valves.  Do not over torque the valves as they are made of brass.

Check to see that you have buttoned everything back up.  Turn ON ignition with the engine OFF.  If all goes well, the low coolant level message should not appear.  At this point I would check the system.  Let the engine heat up and check for leaks.  Watch the engine temp.  The temp should rise and level off.  If it keeps climbing past where it normally would go or the Engine Temp warning comes on, turn the engine off IMMEDIATELY and let it cool down.  Check the fluid level again.

According to the book, the Low Coolant warning may come on at first.  If after three cycles of engine heating and cooling it does not go out, something else is wrong and you'll have to get a scan tool.

Last note, the module was $67 at my dealer!  I should have known it would be pricey when the guy a the parts counter said it was a "module" not a switch.