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Liquid Coolants

Traditionally Macintosh computers have been air-cooled by attaching large aluminum or copper heatsinks over the processor. These heatsinks have fins that are fan-cooled.

The Power Mac G5 (June 2004) Dual 2.5 GHz model was the first Power Mac to include a liquid cooling system, which is considered a “closed-loop system.” This means the cooling fluid is completely sealed within the tubing and you don’t have access to the fluid to refill or change it.

The liquid cooling system fluid is predominantly water (80 percent or greater) with a mixture of corrosion inhibitors, antifreeze, and bacterial growth preventatives.

Although having a closed-loop liquid cooling system provides a higher degree of safety when using liquid cooling, there still can be some circumstances in which the liquid cooling system is defective and causes a leak.

You might visually identify a coolant leak if you happen to be near the computer when it is on. Since the liquid is under pressure, you may see or hear squirting. Once the processor reaches a certain temperature (due to a lack of cooling), the computer will power itself off to prevent further damage.

If you ever suspect that a liquid cooling system fault is present or involved, you should pull the power cord from the computer or wall socket immediately. Don’t just turn off a power strip. Once the computer is powered off, you can open the case to determine if there is an overt leak.

Evidence of leaks includes corrosions around fittings in the liquid coolant system, the presence of a light green or red liquid, or a slick or slimy feel when handling the part. If you perceive any indication of a leak, service the computer immediately (if you’re an AASP technician).

Wear nitrile or rubber gloves when handling a liquid cooling module that is leaking or suspected to be leaking.

Place the failed liquid cooling module (leaking or not) in the bag the replacement came in, seal it, and return it to Apple.

For coolant leaks or spills, absorb the material using rags, paper towels, or other suitable materials. Contain and dispose of all cleaning materials according to local antifreeze-disposal laws and regulations. Do not combine used coolant with any other chemical.

For complete instructions on working with liquid coolants, refer to the Material Safety Data Sheet (MSDS) for the liquid:

  1. Open
  2. Click the MSDS link for the Power Mac G5 Dual 2.7GHz, red liquid.
  3. Skim the document.

Liquid Coolant Safety Quiz

Read the MSDS for liquid coolants and answer the following questions.

  1. What should you do if you get some liquid coolant from a Power Mac G5 in your eyes?
  2. What happens if you get some liquid coolant on your hands?

Answer Key

1. Rinse the eyes with water, get immediate medical attention; 2. The skin on your hands could get slightly irritated

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