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I have been researching on the web and have seen that Dexcool seems to be the culprit in many cooling system problems on GM cars. But if Dexcool was as bad as it seems, almost literally, millions of vehicles would have cooling system problems, not the relatively low numbers that have been seen to date. This is not to indicate that the issue doesn't exist, but it does look like Dexcool may be a victim and not the root cause. As an engineer, when one looks for a reason for a system failure isolating the root cause is critical to understanding and correcting the problem.
On todays' vehicles the frame and/or body sheet metal serve as the primary grounding device for the electrical system. If properly connected, it is in fact an extension of the electrical negative return path to the battery connection. Although the body is typically isolated from the chassis by cushioned insulators, the supplemental ground wires connected to each vehicle body are connected back to the chassis and the battery by one or more body-to-frame jumper wires.
While the vehicles of 30 years ago may have had just a few ground wires, it is quite common to have between 10 and 20 chassis-ground connections sharing the load today. Each and every connection must be functioning properly to complete the circuit and route the flow of electricity back to the battery. Any broken, loose or corroded connections are almost sure to cause a malfunction and alter the flow of electricity. Under these conditions electrical current will stray from its intended route and create a return flow by the path of least resistance.
In any vehicle that has the Dexcool cooling system problem be suspicious of ground wires. Even in new vehicles it is possible for bad connections and current flow problems. Furthermore damage to ground wires is almost inevitable with vehicle age, accidents or poor installation practices of electrical equipment. In a collision grounds can be damaged creating conditions for a Dexcool cooling system "failure". When grounds are securely connected, the electrical path is well defined. Any connection breach will cause the electricity to find another path of least resistance. Particularly for electrical components or circuitry in close proximity to the radiator or heater—that path can involve the coolant itself.
On cars with the coolant system issues I strongly suggest you check for electrolysis, use a good digital voltmeter set for 12 volts. Do this test both key on and key off. Attach one test lead to the negative battery post and insert the other test lead into the radiator’s coolant, make sure the lead does not touch the filler neck or the radiator core. You may see a surface charge that could be 0.7 volts or higher. Be patient as it could take up to two minutes for this surface charge to dissipate. Give the measurement time to stabilize (at least 2-3 minutes) A voltage reading of 0.3 VDC or higher indicates that stray current is finding its path to ground through the cooling system. Now the fun starts. With the meter probes in place remove accessory fuses one at a time, wait 30 seconds and read the meter. If you find a circuit that drops the meter to near zero or below 0.3 VDC when you pull it's fuse you've found the offending circuit. At this point you need to check the grounds of the items on that circuit. Remember that a motor could be internally shorted and have case leakage causing problems.
If after the fuse pull test you can't locate the offending circuit remove the negative battery lead. If the voltage drops to an acceptable level a general system ground check and connection cleanup is in order. When cleaning connections I pull them off and add star washers to assure good metal to metal bite and minimal path resistance. This technique has served me well on cars with electrical gremlins of all kinds...
Good Luck
Andromeda
On todays' vehicles the frame and/or body sheet metal serve as the primary grounding device for the electrical system. If properly connected, it is in fact an extension of the electrical negative return path to the battery connection. Although the body is typically isolated from the chassis by cushioned insulators, the supplemental ground wires connected to each vehicle body are connected back to the chassis and the battery by one or more body-to-frame jumper wires.
While the vehicles of 30 years ago may have had just a few ground wires, it is quite common to have between 10 and 20 chassis-ground connections sharing the load today. Each and every connection must be functioning properly to complete the circuit and route the flow of electricity back to the battery. Any broken, loose or corroded connections are almost sure to cause a malfunction and alter the flow of electricity. Under these conditions electrical current will stray from its intended route and create a return flow by the path of least resistance.
In any vehicle that has the Dexcool cooling system problem be suspicious of ground wires. Even in new vehicles it is possible for bad connections and current flow problems. Furthermore damage to ground wires is almost inevitable with vehicle age, accidents or poor installation practices of electrical equipment. In a collision grounds can be damaged creating conditions for a Dexcool cooling system "failure". When grounds are securely connected, the electrical path is well defined. Any connection breach will cause the electricity to find another path of least resistance. Particularly for electrical components or circuitry in close proximity to the radiator or heater—that path can involve the coolant itself.
On cars with the coolant system issues I strongly suggest you check for electrolysis, use a good digital voltmeter set for 12 volts. Do this test both key on and key off. Attach one test lead to the negative battery post and insert the other test lead into the radiator’s coolant, make sure the lead does not touch the filler neck or the radiator core. You may see a surface charge that could be 0.7 volts or higher. Be patient as it could take up to two minutes for this surface charge to dissipate. Give the measurement time to stabilize (at least 2-3 minutes) A voltage reading of 0.3 VDC or higher indicates that stray current is finding its path to ground through the cooling system. Now the fun starts. With the meter probes in place remove accessory fuses one at a time, wait 30 seconds and read the meter. If you find a circuit that drops the meter to near zero or below 0.3 VDC when you pull it's fuse you've found the offending circuit. At this point you need to check the grounds of the items on that circuit. Remember that a motor could be internally shorted and have case leakage causing problems.
If after the fuse pull test you can't locate the offending circuit remove the negative battery lead. If the voltage drops to an acceptable level a general system ground check and connection cleanup is in order. When cleaning connections I pull them off and add star washers to assure good metal to metal bite and minimal path resistance. This technique has served me well on cars with electrical gremlins of all kinds...
Good Luck
Andromeda
Last week, a friend of mine was having an issue with a quad driver in the ECM on a 95 sunfire with a 2.2. Rebuilt 2.2 with new sensors galore and all the grounds gave a continuity check sound from the volt meter. I have known bad sensors to cause quad driver issues but in this case, it was the quality of the ground that was the problem. 
) Multiple / different metals have been used in cars for many years but recent developments with respect to engine and chassis management is a relatively new development. I will be doing some testing this week to determine if there is a "shotgun" fix that can be applied cheaply to the vehicle to assure reliability and lower TCO (total cost of ownership) I'll make sure I post the results here. A far as Dexcool goes I can't comment yet on the organic versus no-organic anti-freeze question yet. At first blush it looks like dexcool is just a coincident player and the real culprit is stray current. After reading the comments that place a conspiracy theory behind every thing GM does I find the only way to be sure is to have data to back up the opinions. I don't see GM as the bogeyman corporation here. They don't deliberately design a bad car nor do their engineers have to deal with 7 year old vehicles and their problems! Data will tell all.
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