does you water temp drop in the winter? - JeepForum.com
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Unread 12-03-2010, 07:33 AM   #1
autopc25
Registered User
1997 TJ Wrangler 
 
Join Date: Jan 2010
Location: il
Posts: 484
does you water temp drop in the winter?

I replaced the thermostat last May and assumed the replacement was a 195 degree unit. My water temp was a steady 200 (just a little to the left of the 210 mark) all spring, summer, fall. The temp was always the same in bumper to bumper, highway, A/C on and off.

My water temp seems to have dropped now that it is winter and about 25 degrees outside. I checked the hoses with a infrared thermometer. The upper radiator hose was about 100, top heater hose 147, bottom heater hose 136. The air temp blowing out of the heater vents inside was about 145. I assume the thick rubber hose is insulating the coolant for the upper radiator hose so that reading is way off? I checked when it was 25 degrees outside.

I seem to remember my normal operating temp being just a hair under the 210 marker last winter. I am not 100% sure though? This year I flushed out the heater core a week ago. I noticed my water temp gauge needle bouncing between 180 and 190 then I realized I did not replace the loss coolant, about a quart. I added the loss coolant yesterday thinking that might be the problem. The overflow tank was at a normal level before the flush and almost empty after flushing the core so I assume all that coolant got sucked back in to the radiator? I topped off the coolant by pouring new coolant into the overfill tank. The needle does not seem to move as much but it still around 190. (I assume the fluctuation was due to not enough coolant and bubbles in the system?) It never gets to 200 like in the summer. I plugged in a scanner and looked at the temp readings and it looks like the gauge in the dash is accurate. Temp is 190. A 195 degree thermostat should be hotter then 190 right?

I am starting to wonder if I was given a lower temp thermostat by mistake or is my water temp sender starting to go bad?

Would a bad temp sensor cause the reading so move up and down or wrong? (I assume this was caused by the low coolant because it has stabilized). Or will a bad sensor just stop working?

Or is the thermostat bad and opening too soon and not closing fast enough?

Could the gauge needle for the temp be moving by not having enough coolant?

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Unread 12-03-2010, 08:04 AM   #2
base shakers
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2005 LJ Wrangler 
 
Join Date: Jul 2005
Location: Somerville (Boston) MA
Posts: 904
it is throwing any codes? i may have a similar problem, on cold mornings the computer thinks the jeep is taking too long to warm up and throws a code saying the coolant temp is below the thermostat temp. it eventually gets there, but it takes a while.
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Unread 12-03-2010, 08:14 AM   #3
autopc25
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1997 TJ Wrangler 
 
Join Date: Jan 2010
Location: il
Posts: 484
Quote:
Originally Posted by base shakers View Post
it is throwing any codes? i may have a similar problem, on cold mornings the computer thinks the jeep is taking too long to warm up and throws a code saying the coolant temp is below the thermostat temp. it eventually gets there, but it takes a while.
No codes at all. My TJ warms up after a few minutes and runs fine. I guess my main concern is if my thermostat is a 195 degree unit? Or if coolant temp sensor might be bad?
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