Engine overheating inconsistently

1996 GMC SUBURBAN
160,000 MILES • 7.4L • V8 • 4WD • AUTOMATIC
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AAROWBAL
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  • 1 POST
After starting engine in morning, with ambient outside temperature being approximately twenty five to thirty degrees F, I let the engine warm up up for five minutes or so.
When I drive off, I get about three and half miles out and notice that the temperature gauge is past normal and rising toward max temperature and there is cold air blowing out of vents. I pull over as soon as possible and put in park and leave engine running then not knowing exactly what the problem is, I rev up the engine a couple of times and sometimes it works but the gauge needle starts dropping and there is heat now coming out of the vents. It does not always work. This happened a couple of times and then I replaced the thermostat. I then tried driving again after letting the silicone gasket cure and still had inconsistently the same problem.
Not sure what the problem is. Any Ideas would be greatly appreciated!
Jan 27, 2017 at 11:17 AM
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HMAC300
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  • 48,601 POSTS
check coolant level make sure is full, then pressure check for an internal leak.
Jan 27, 2017 at 12:04 PM