CC57 Posted December 12, 2008 Report Share Posted December 12, 2008 '99 Suburban with a 5.7 liter. Here are the symptoms that either just started recently or I just happened to notice it recently: Has the engine gradually warms up, the water temp gauge jumps up to around 230, sits there awhile and then jumps down to 140 to 160. It may even jump back up and hover around 210 for awhile, but then settle back down around 140 to 160. Defective or going defective thermostat perhaps? Thanks all Link to comment Share on other sites More sharing options...
racer61 Posted December 12, 2008 Report Share Posted December 12, 2008 Sounds like a thermostat. Are you sure its full. Air pockets cause the same thing too. Hope it helps. Link to comment Share on other sites More sharing options...
Crazyhorse Posted December 12, 2008 Report Share Posted December 12, 2008 thermostat , or cavitating Link to comment Share on other sites More sharing options...
CC57 Posted December 12, 2008 Author Report Share Posted December 12, 2008 Thanks guys. I'll check the fluid level tomorrow. And just to be on the safe side, I'll probably replace the thermostat. They're inexpensive enough and easy to replace. Thanks again. Link to comment Share on other sites More sharing options...
doninaustin Posted December 12, 2008 Report Share Posted December 12, 2008 Coolant low or head gasket leak displaces coolant. Don in Austin Link to comment Share on other sites More sharing options...
KISS_Racing Posted December 13, 2008 Report Share Posted December 13, 2008 thermostat , or cavitating With Shawn Paul. T-Stat, Cavitating water pump or even ===>slipping belt<===... Link to comment Share on other sites More sharing options...
1-Crew Posted December 13, 2008 Report Share Posted December 13, 2008 If your description is accurate "jumps up to around 230, sits there awhile and then jumps down to 140 to 160", then it is not real, it is the gauge, sending unit or wiring. 600 lbs of iron does not "jump" 110 degrees... Link to comment Share on other sites More sharing options...
Crazyhorse Posted December 13, 2008 Report Share Posted December 13, 2008 If your description is accurate "jumps up to around 230, sits there awhile and then jumps down to 140 to 160", then it is not real, it is the gauge, sending unit or wiring. 600 lbs of iron does not "jump" 110 degrees... this is the best suggestion......and prolly the right one. Link to comment Share on other sites More sharing options...
97car Posted December 13, 2008 Report Share Posted December 13, 2008 Check your intake bolts to make sure none are broken, I helped rebuild a 98 Chevy that had 2 intake bolts corroded. Link to comment Share on other sites More sharing options...
HiTech Posted December 13, 2008 Report Share Posted December 13, 2008 i would manualy take temp readings of your coolant . across the radiator ..hoses ..heads .and such .....looks to me like its a sending unit or gauge ....... Link to comment Share on other sites More sharing options...
KISS_Racing Posted December 13, 2008 Report Share Posted December 13, 2008 If your description is accurate "jumps up to around 230, sits there awhile and then jumps down to 140 to 160", then it is not real, it is the gauge, sending unit or wiring. 600 lbs of iron does not "jump" 110 degrees... on edit: (Oh never mind....) Link to comment Share on other sites More sharing options...
wheelchair49 Posted December 15, 2008 Report Share Posted December 15, 2008 put in a manual gauge you can buy them at autozone for around20. no electrical wires to short out i had this same problem with a ford and this told me the gauge was lying Link to comment Share on other sites More sharing options...
CC57 Posted December 18, 2008 Author Report Share Posted December 18, 2008 Ok, first of all, thank you for all of the responses. I belive I learned something along the way. Now the embarassing part. When I first submitted this request, it was at the end of the day and before I have checked anything. And my first assumption (and I should know better by now and not assume.) was the radiator was full. So the following morning, I check the radiator: the water level was down. Filled the radiator, making sure to bump the revs up some so it will pull the water level down before topping off and putting the radiator cap on. Check temp gauge. After idling for a few minutes, the needle slowly rose up and remained steady a the mark midwya between 100 and 210 (around 160, right?). And has been fine since. Once again, thanks all for the repsonse (and stay tuned for "Help Me Diagnose This - Part II" ) Link to comment Share on other sites More sharing options...
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