Erratic temp guage

[racqsixo]

I have a 2006 F350 DRW Lariat crew cab. Last week the temp guage started dropping down off the scale whenever I stop and take off again. The guage usually drops by the time I hit 2nd gear, the A/C stops functioning and then everything goes back to normal within 20 or 30 seconds of normal speed. Sometimes the fan clutch engages as well. The dealer hasn't figured it out yet after a week in the shop. Does anyone have any ideas?

[mschn99]

if it has blown any coolant out of the degas bottle i would suspect a possible egr cooler failure.....