I have a 1997 Blazer LS 4X4 with 201000 miles on it. The small annoyance I have is that the temp gauge goes 1.5-2 lines above the middle 210 line and then drops back down as soon as it gets there and stays rock solid 1.5-2 lines below the middle for the rest of the drive. Like I said it is a very small annoyance that could be nothing, but would like to head any problems off that may arise from this.

 

Sounds like the same thing it was doing as referenced in your original threadfrom a few months ago. If it's not due to air trapped in the coolant system, I would suspect just an inaccuracy in the factory dash gauge.

 

It very well could be a bad guage. Like I said it's a small annoyance but one I can live with.

On an unrelated note, I just finished replacing the upper and lower intake gaskets for good measure and found an amazing amount of pitting on the underside of the lower intake at the rear water jackets. There should have been some sort of crossover made for that area to prevent this type of problem.

Also just a quick note about the intake bolts, they are crap and will break when retorqued on the lower intake, so if you are thinking of doing this get different bolts to have on hand just in case.

 

I have seen this phenomenon in a LOT of vehicles. This can be due to the location of the gauge sending unit in the engine. My K5 does this and it has a 1 wire sending unit for the engine temperature. My Chevelle would also do this with a fully mechanical gauge. Both would climb to over 210*F and then drop down to ~195*F.

My theory is this; due to the location difference between the sending units (driver side cylinder head) and the thermostat (front/center of the intake manifold), the heat seen at the sending unit reaches a higher temperature than that seen at the thermostat for a short time period as indicated. Once the thermostat opens and coolant flows through the block, the temperatures normalize more evenly and control is asserted.

I would say that it is nothing to worry about. This would be especially true if your coolant level is holding steady.