I have a 2004 H2 with 125,000 Miles on it, I've had it since day 1 and have done all maintenance and work to it myself. The other day out of the blue I noticed that from a cold start up the Engine Temp gauge was going up to 235 and then dropping bak to a normal 200-205 where she always runs. when i drive I'm constantly looking at the gauges as a old habit i got into when i learned to drive. so i figured okay this is more then likely the Thermostat getting stuck. I was tinkering around with it today and notice at a dead stop idling the Temp runs at 200 but if i hold it at around 1,500 RPM's for about 30 seconds it climbs to 235. then if i increased the RPM's to 3,000 it drops bak down to 200-205 ish. This only seems to happen from a cold start up or if I'm at a dead stop, on the road or freeway it runs at normal Tempeture.
with almost all of my GM vehicles I've had over the years, family and friends its almost like clock work once you hit around 100,000 miles its usually the Waterpump, Fuel Pump and or Altenator that seems to be coming to time to replace it..
However my H2 is an Exception i haven't had to do a thing to it just normal Maintnence and what not. My question is that that now i seem to be getting a little issue with the Temp is it my first warning sign that the Thermostat and water pump are coming up to be replaced? the water pump is not leaking at all and the fan is tight with no play in it.
Any Advice is highly Appreciated it is my Daily Driver so I just wanna get some opinions before i dig into it and start replacing stuff !

Thanks, and Merry Christmas!

 

If the pump is not leaking and there is no play in the bearing I would bet it's OK. I would do the thermostat and a good radiator flush and then see what happens. Stant makes a good thermostat.

 

Yesterday I Installed a New Waterpump and a Hypertech 160Degree thermostat, and Flushed the Radiator....My H2 now runs cooler the it ever has around 175-180 degrees compared the 210 it was running ! since i had it all apart i also installed new hoses, Serpentine Belts and Spark Plugs and wires !... Hopefully Now everything will be okay ! .. Thanks !

 

Your truck was designed for and needs a 195 degree thermostat. A lower thermostat can cause an decrease in MPG as the engine will not get up to operating temp. and the computer will add more fuel thinking it's still warming up.

Glad you got your overheating problem solved. Did you see anything visible signs making the water pump defective?

 

When i first Posted this Thread i did not see any leaks from the water pump that i could see, However when i took off the H2 Skid plate there was a big puddle of Coolant sitting on it and dripped over myself ! LOL... i took my flashlight and looked underneath the motor and found that the Water Pump Was indeed leaking from one of the gaskets and out of the Weep Hole as well ! so i just went ahead and replaced it.

 

Most times when you car overheats while at idle or slow movement it is the fan clutch not locking up.
Even though the pump might be leaking it would not normally cause an overheat problem.
Good luck.