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something weird was happening with my termp guage... help?

MaxxXJ

NAXJA Forum User
Location
Bakersfield CA
ok... so here's what i noticed for the first time last night. i drove my xj all over running 210 no problem... thats fine, well about 1:30am last night me and my girl get done watching the meteor shower and i go to drive home and when i get on the freeway doing 60mph my temp guage drops to the line below 210 im assuming around 180, i hop off the freeway and get on a street doing about 35/40mph and it gets just below 210... i stop at a stop light and idle for a second and sure enough it goes back up to 210 as normal... but when i take off and kick it back up to 50-55, sure enough it goes back to almost the 180 mark. it wasnt real cold last night but i'd say it was maybe 70-75 degrees. im going to drive it today in the 90+ weather and see if it still does it, has anyone else had this problem and if so what was the problem?
 
ok, so i replaced my thermostat and it fixed everything, dont be alarmed... i fixed it, i also changed my plugs, it looks like they had 115K miles on them... hopefully my gas mileage will go back up...
 
oh yeah... you should of saw my thermostat =) how it has the spring and an arm on each side to hold it on... only there was only 1 arm still holding it on, the other one broke and was just hanging there... there was a weird thing though, my thermostat housing had an odd color to it, it was like sulfurish yellow... i'll figure that out later i guess
 
Going to hyjack this thread since I DO have a weird temp question ;)

Everything was workign fine. ran 210. Found out i had a blown headgasket. Replaced it. burped the system. Temp guage worked fine.

Then about 30 miles later i noticed the temp never went past the first mark (the one between 100 and 210). its jsut staied there. And its been like that ever since. Halfway between 100/blue line to the first mark is normal. If i hit 210. its like im passing the redline (i did this while pulling a second Jeep down the freeway) at 210 Im boiling over.... Any ideas on now to make my temp guage work normally?

I have check the connectins and they all seem to be normal.
 
I would check out the tstat. I never saw one happen like this before, but my son's Escort had wierd temp fluctuations. Finally got him to pull the tstat and one of the two arms that support the center section was broken like MaxxXJ. It did have over 100k miles on it too.
 
I have seen the temp gauge drop really low several times, but it typically related to running higher RPMs. For one thing the water pump really starts pushing coolant at that speed and there is a lot of pressure at the thermostat and the heater bypass. Second is that the clutch fan will lock itself at about ~3000 RPM or thereabouts, so when I am running at higher RPMs the clutch engages and the higher fan speed pushes the engine temps way down. This usually happens when I am driving around in 3rd (Overdrive disabled) and forget to put it in D before getting up to speed.
 
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