why does my temp gauge go from normal to hi and back in a few seconds as I'm driving?

1998 GMC C1500
210,000 MILES
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STRIDER190
  • MEMBER
  • 1 POST
Goes up and down, problem comes and goes. Yesterday truck overheated, steam from under hood. Also the heater doesn't work.
Mar 19, 2012 at 6:59 AM
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WRENCHTECH
  • ✓Experienced Mechanic
  • 20,760 POSTS
That means that there are air pockets in the system that could be from a leak or possibly a blown head gasket. You need to pressure test the cooling system.
Mar 19, 2012 at 7:17 AM
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