[HO455]

Does your zinc anode show any degradation? If not as previously stated it's not doing its job.

Use the best ohm meter (Old Simpson 260's are good for this) you can find and check the resistance between the anode and the radiator. It needs to be zero. Electrolysis is the flow of electrons if the anode is electrically isolated no electron flow will occur and the radiator will not connected to the sacrificial zinc alloy and as a result may be sacrificed.

It is tough to put an exact voltage that may be too much, as coolant flowing over dissimilar metals contributes to the erosion of the weakest metal. That part of the erosion process is difficult to measure or diagnose. So what one vehicle is okay with, the next one will fail with that same voltage

Coolants have corrosion inhibitors in their formulas and are meant to prevent electrolysis between dissimilar metals. They however may not prevent electrolysis between every conceivable combination of alloys. Doing an inspection for any non GM components that are in the coolant would be a good start. Like temperature senders. If you have a real electrolysis problem your coolant protection can be used up in 20 hours or less. In the commercial marine world we do periodic testing of the coolant to ensure protection.

On the electrical side electrolysis is compounded by stray electrical current flowing through the coolant. Checking the voltage in the coolant is a start. Did you do it with engine running and shut off? How about not running with the key on?

Try using a multimeter and see if any of the sensors are partially grounded. On an LS this might be easier if the harness was unplugged from the ECM and you tested each wire to ground with the battery leads disconnected.

Electricity takes the path of least resistance and it may be that an something not related to the cooling system is where the current is coming from. Also make sure none of your engine ground leads are attached to a bolt that is exposed to coolant. That path of least resistance may be using the coolant to get back to the battery.

From my experience on tugboats I would not run a lead to battery from the anode as that doesn't find the source of the electrolysis it merely is an attempt to mask the symptom. The result of that may be the electrolysis is still present but now attacking a different part.

I'm sure I've forgotten lots but my battery is dying, so it post or loose it.