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Test 18 - Air Switching System Check

  1. Remove air cleaner. Disconnect the downstream air hose from the switch/relief valve. Start engine. With engine coolant more than 150°F (67°C), air should be coming from downstream air port of the switch/relief valve.
    NOTE: Some systems have a 125°F (51°C) temperature switching point.
  2. If air is coming from downstream air port, proceed to TEST 19  . If air is not coming from downstream air port, proceed to step 3).
  3. Disconnect vacuum hose from air switch/relief valve. Connect a vacuum gauge to hose. Vacuum gauge should read zero in. Hg vacuum. If vacuum is okay, replace air switch/relief valve. If there is vacuum, replace CVSCO valve.
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