So I changed out the t-stat today for a nice new 195deg one in my 95 Jimmy due to the nasty feeling that the one in the truck was about to fail me... I would start driving and would watch my temp gauge go to just over 215, then drop to just barely above the tick mark half way between the 100 and 215 mark. I didn't like how hot it had to get first, so I swapped it out..

Now I am having a fluctuation in the gauge reading while driving... Once it gets up to temp it will float between almost at teh 215 mark, and then drop to one mark above the mid point from 100 - 215... Yea, that is a bit odd of a description so here are a couple pics of it both the hot reading and the cold reading...

Cold (seems to be just a touch colder sometimes)


Hot (couldnt get a shot when it was at the hottest mark it hits, traffic wasnt cooperating...)


it only takes about 10 - 20 seconds for it to drop from the hot temp to the cold and then it slowly climbs back up to the hot reading again.

When I did the T-Stat, obviously there was water loss from the rad side and the hose, and once I popped the T-stat out more water flowed out the block. After I got everything back together I added coolant and water to the rad to bring it up to full, and then I started the truck and let it get up to temp so the T-stat would open and allow water into the block to replace the lost coolant. well it got up to about 215 on the gauge and then dropped to the mid mark then warmed back up.Kinda stabilized the temp at this point so I opened the rad cap to add coolant, but it really didn't take much. I let the truck idle for about 45 mins, (Dont ask, I forgot it was running while I searched this forum on how to burp the system) then checked the level and it still hadnt dropped much. For some reason I thought it would be a good idea to stick my finger into the rad and see how hot the coolant was, and it was maybe barely over 100. I mean I could hold my finger in it and not get burned... was thinking the coolant should have been hotter. that and there was no pressure in the system when I took off the cap.

well I decided maybe I should drive it a bit to see if the coolant would cycle better on the road. on the highway speed constant at 65 and my gauge wouldn't touch 215, but started doing the fluctuation thing... I drove it about 30 miles and am now letting it cool off with the passenger tire on a ramp so that that corner of the truck is higher and I will see if there are any air bubbles that want to come out...

Any other ideas?

Anyone? bueller? Bueller?

drove it some more, and still cant seem to get any air bubbles out of it, thinking that maybe it is supposed to be moving as the T-Stat opens and closes? but that dont make much sense....

 

Same problem here!!!! Get it fixed??

 

Good Day! I have posted before my same experinces with these gauge clusters,and after making sure t-stat fine & no air in system-still remained the same problem:except mine reads cold all the time! Swapped the sender with no results,then installed a temporary mechanical gauge and found that all was indeed normal over several weeks time. Removed the temporary gauge and now just monitor & maintain my cooling system annually(and look at it weekly)Heat is great too! So? Gauge cluster issue IMO! I'm just living with it in a 15 year old car! It is was it is,unless you want a new cluster! Mines a 97 by the way-about the same as yours! Just my opinion!step66

 

That looks like the exact range on mine when the t stat opens and closes. Maybe you just kind of started to notice it. I now when I noticed I was staring at mine.