Engine running slightly cool...?

[AcIdBuRn02ZTS]

Hey guys...

I picked up an 03 z71 tahoe last week. It drives great and I didnt notice any issues with it for the first day of driving... however after letting it sit overnight, it started running cooler then it should.

Ive been driving it for a week now and the gauge will come up to around 175... hold there for quite some time and then randomly come up to 210 but will slowly drop back down to around 175 or so shortly after... I figured the t-stat was sticking open or something..

Replaced the t-stat and still have the same problem. The heat blows hot and the coolant it full/clean. Havnt seen any leaks. Today on my way home from work, I hooked up the shops snapon scan tool and monitored the ect from the ecu just to make sure the gauge wasnt acting up... It warmed up decently quick but only got up to around 180... then 10 miles later, it finally came up to 190 (reading 205-120 on the gauge) which I then pulled into the driveway and just let it idle... no air moving what so ever and the gauge dropped back down to the 175ish range and ecu reading progressively dropped to around 180-183 and would go slowly back and forth from 190-180...

The t-stat I installed was a Murray brand and OEM temp (187 I think...)

My question is... with a 187 degree t-stat... why did most of my drive home in 95* heat did the truck only reach 180? What would cause it to run cool or show running cool on the gauge and ecu besides the t-stat?

Anyone have any issues like this? Most gm vehicles Ive driven, the temp gauge comes up to 210 and stays put... Ive never had one just drop back down at random.. And its never overheated on me or anything like that... So I'm somewhat stumped...

Thanks for any help
-Chris

 

[blueflamed03]

seems stock Tstat range should be like 205ish?
Mine runs 205 give or take all the time.

by looking, your right, stock calls for 187.

 

[hoe]

the stock cluster is inaccurate. Just use a scan tool to tell the tail. I run a 180tstat and my gauge shows the same range as the stock tstat. But in my tune and live scan you can see the difference.

 

[AcIdBuRn02ZTS]

the scan tool also shows it running a bit cooler then it should be... as stated above.

Thanks
-Chris

 

[hoe]

maybe just a good water pump man, I would not be concerned unless its runing slightly hotter. Also make sure its no air in the system. While its runing, top off the resivor etc.