A few months ago I bought a 97 Sierra 5.0. I noticed the
coolant was in bad shape. I took it back and I don't know
if they flushed but it seemed to have decent Dexcool then.
It started to overheat and leak big puddles from oil pan area.
I couldn't see leak anywhere but did notice wet around intake.
I took it back and they pressure tested and said they couldn't
find leak. They ended up replacing hose part that goes into
intake manifold. It was corroded and broke when they took off.
Now it doesn't seem to leak but I always notice a slight smell
of coolant when I get out. I noticed they put green coolant
in it and the tech said it was OK when I mentioned it should
have Dexcool. The coolant looked like crap so I flushed it
myself and I'm using the green now after seeing the concerns
with Dexcool. Seems OK but the temp seems erratic. First, it
gets to about 210 till I guess the thermostat opens then
it fluxuates from about 160 to 210 the rest of time.
My ?s ARE: is this temp flux normal?
Should I replace intake gasket if suspect? And what's involved
with replacing upper gasket?
Where would you go from here?
Thanks guys.

I have a similar problem, I have the erratic temperature readings. lthough I have been attributing them to having a Western plow mounted to the fromt of my truck. Today I installed a new thermostat rated at 160 degrees. Around town this seems fine, however I still get the erratic readings on longer trips ( say 15 minutes or more without stopping for lights ), I am looking into replacing the temp. sensor and installing an auxillary fan that mounts between the radiator and the grill of the truck. I will let you know my outcome, but any new revolations would be great.
Mike
Colonia,NJ

Thanks for the reply. I think I read somewhere in this forum that
you might need to do something else to the temp. regulator or
computer or something to get the benefit of the new lower
temp. thermostat.
I'm sure one of the pros in here knows what's up.

I have a 160 thermostate in my 1500 350 5.7l and the readings are steady 160. I just need now the perfomance chip to take full advantage of the thermostate

I am having a similar problem. When the truck first warms up the gauge will go up to 210 and then settle down to 190. The gauge will stay at 190 until I either slowdown or come to a stop and it will then go down to around 160. Then when I speed up it will go back to 190 and stay there until I either slowdown or stop again. I have replaced the thermostat and fan clutch. Contiplating replacing the Temp switch/sender. (NOTE) when purchasing the temp switch/sender for 98 chevy silverado's 3/4 ton the wire is to short. Went to the dealer and the wire is barely long enough. Any other ideas would be great.