This might sound like a dumb question, but I'll ask it anyway. Are you sure your fans are blowing in the right direction? I know it's possible to accidentally mount the main fan backwards and wire the aux fans in reverse.

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"It's not about how fast you can go, but how well you can go fast."

Bob in Richmond

'97 S320 (LWB), Ruby Red Metallic, 73k miles
'97 S420V, Smoke Silver Metallic, 155k miles