ok this is the issue..i have an 02 tj 4.0...i had i mild overheat issue back in jan. ... after that the temp gauge would peg then go back down to 230ish without overheating...it normally ran a solid 210...just out of curiosity i pulled the tstat and change temp sensor...now it will periodically go to 220 while driving then drop at idle...next day it stays at 210...heat will flutuate...what direction should i go? flush...new tstat then see what happens....and could it be hg?thanks for any help
Cooling system help
- Thread starter muddpuppi
- Start date
When you pulled the T stat, did you replace it with a new one? And not that this would specifically cause your issue but those Tstats go in a certain way double check that
And get a factory T stat for best results
no tstat yet...i just pulled it and resealed...i have not had a chance to put one back in....will do that tomorrow hopefully...workin nights this week..l can understand it running a lil cool on the heater but it fluctuated temp at a constant rpm
How many miles on the motor and water pump? - make sure the accessory drive belt is good n snug. If the drive belt is loose it won't turn the water pump enough to circulate the water
less than 15000...changed last yr...belt seems to be normal...now i am limited on funds so it wasnt oem pump...
This may sound like the most obvious thing, but have you checked the radiator when it's been sitting for an hour or so (completely cool) to make sure it's 100% full? Mine was doing just as you described, and it turns out my radiator was only half full!
You can't run without a thermostat and not expect the temperature to fluctuate and drop at idle rpms. Install a new 195 degree thermostat, your previous problem was caused by a sticking thermostat. Make sure NOT to use any thermostat labeled as "fail-safe" (they're not, they produce their own problems) and make sure to avoid installing a lower temperature thermostat like a 165 or 180 degree model. Everything on the TJ is built/programmed around having a conventional 195 degree thermostat installed.
Make sure to just use a gasket to install it, no RTV, and make sure both gasket seating surfaces are 100% clean. Use a wire brush or scraper to get every last little piece of the old gasket off.
Make sure to just use a gasket to install it, no RTV, and make sure both gasket seating surfaces are 100% clean. Use a wire brush or scraper to get every last little piece of the old gasket off.
i can understand it dropping without the tstat what gets me is it will still go well above 220 without it
A sticking thermostat can cause that but if it's going over 220 without the thermostat in place, that could be caused by several possibilities. 1) Calcium deposits from using hose/tap water to mix with the coolant instead of distilled water. 2) Radiator fins clogged/blocked from dried mud/dirt. 3) A poorly designed/store-brand aftermarket radiator. Few radiators cool as well as the OE Mopar radiator does even in extreme conditions. 4) A bad fan clutch if it tends to run hotter when idling.
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Understanding how a thermostat really works is critical to troubleshooting one. Many people think that if you remove the thermostat the engine will run cooler .. WRONG! ... Engines get very hot and need water to cool them.
A TJ has a 195 degree thermostat, meaning it doesn't open or allow water to flow through it until that temperature, so once the water in the engine block starts to approach 195 degrees it opens and allows the water that has been cooled in the radiator to replace the water in the engine and let the radiator start the cooling process all over again.
If there is NO thermostat, the water continues to circulate and is never given the opportunity to cool in the radiator. The engine runs very hot and that water will continue to heat and eventually reach its boiling point and then all the bad things happen.
A TJ has a 195 degree thermostat, meaning it doesn't open or allow water to flow through it until that temperature, so once the water in the engine block starts to approach 195 degrees it opens and allows the water that has been cooled in the radiator to replace the water in the engine and let the radiator start the cooling process all over again.
If there is NO thermostat, the water continues to circulate and is never given the opportunity to cool in the radiator. The engine runs very hot and that water will continue to heat and eventually reach its boiling point and then all the bad things happen.
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makes sense...im going to put tstat in in the morn...see what happens....i worried about head gasket leak...didnt have an issue until it overheated in jan due to bad stat...had problems every since but only while running at speed...at idle its fine...i had a ranger do it because exhaust gas was entering cooling system but no external leaks....wondering if that could be the issue...im going to flush it also...dont want to pull head if i dont have to
Just do a pressure test on the cooling system to see if you have a leak anywhere. Any rad shop can do it or you can purchase a setup on Amazon or somewhere.
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You can also look for bubbles at the Rad cap. That would tell you if something is inducing pressure into the system.
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