So the V8 has an auxiliary pump? There must be a little fan and grille to draw air in for the IHKA (like the E53) have you checked that? I would think you should be able to run and monitor everything in ISTA. You're saying that engine coolant temp stays steady when this is happening?

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1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)