Whenever I start my truck up for the day, the temp. gauge goes up normally until it hits 200. It will go over 200 to about 210, then in about 5 seconds (literally) will go down to 175-180, and bounce around from 190-200 as I drive. On the highway it's a steady 195. Could it be the gauge, water pump, head gasket?..etc..

 

I would check the coolant temp sensor, I believe you can check the resistance after the truck is warmed up, turn it off and pull the connector off and test it.

 

i know the sensor is a 1-wire. how would i test that?

 

Actually, that reaction is probably correct. It is reading temp as coolant gets hot, then as stat opens, the temp goes back down as coolant circulates. If you are running a 195 stat, then it should hover between 190 and 200.

 

I do have a 195. Is it normal for it to go to 210 (maybe 205) for a couple seconds only once during the day when I first drive?

 

Check electrical connection to make sure it is secure. The gauge is not entirely accurate, but as long as it does not stay high and truck is not overheating you should be good. Bouncing around may be indication of loose connection or poor ground. Maybe remove and clean threads. Rust can be an inhibitor for good electrical contact. Don't use Teflon tape.

 

I actually broke the connector where it snaps into place while doing the plenum. It's just sitting in there. Before the plenum it never went above 200 but did bounce around a little bit and drop down to 180 once a day.

 

I would start by fixing that!

 

But its weird that it reads 195 all the time on the highway, but around town when rpms fluctuate the gauge moves a little. its probably nothing, the gauges cant be dead accurate

 

All 3 of the Rams I have owned (1999, 2001, and my current 1996, all 5.2L) get to about 210-220 before the t-stat opens, then it drops back down to about 180-190 or so. I will see it get to 200-210 when hauling/towing on a hot day, or sitting in traffic. So I would say a little fluctuation is normal.