2001 Kia Optima thermostat


Old 09-11-11, 02:07 PM
Thread Starter
Join Date: Sep 2011
Location: usa
Posts: 2
2001 Kia Optima thermostat

I sure need help. I recently got a used Kia Optima. Runs great - but overheated when A/C was on high. I figured it was my thermostat and decided to put new one in. Right in front of where thermostat is there is a small black box with 3 wires in it - 2 black and one red. I had to move these to get to thermostat. When I pulled plastic casing it crushed in my hands. Must have been old. I replaced thermostat, replaced fluids that came out when un hooking hoses, and started it up. It started fine and check engine light even went out. Then it stalled. I started it again - it stalled again. I tightened 3 wires back in (hoping I had put them in the correct position - I figured red went in the middle but wasn't sure) and car will not start. It turns over fine, but wont start. I can not figure out what the problem could be and do not know what those 3 wires are for or what they are called. Please help!!!
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Old 09-11-11, 02:43 PM
ukrbyk's Avatar
Join Date: Mar 2010
Location: USA/ Pacific NW
Posts: 3,191
well, don't fix it if it ain't brok. that your car overheats with a/c running, does not necessarily means it's bad thermostat. loose belt. worn out water pump. both. poorly performing radiator.

i'd safely guess, "box" was temperature sensor, if it was part of thermostat housing. black is normally ground and red is normally 12V. some cars won't start without temp sensor functioning. if it was a free standing piece, not part of cooling system, then who knows. start with checking all fuses, but disconnect those wires first, in case you have them crossed. read error codes.
Old 09-11-11, 02:52 PM
Join Date: Mar 2009
Location: Texas
Posts: 1,051
I just noticed another posting from ukrbyk as I was writing this but since it is written.....

Does it look like the black box was a harness connector? Without knowing the vehicle I am wondering if this was the top half of the coolant temperature sensor. Under where the wires go into is there a head for a wrench to fit on to? Temp sensors screw into the block and have a black plastic 3 wire connector on the top that a wire harness plugs into. I am thinking exactly the same as ukrbyk. Probably less than a $25.00 part.
Old 09-11-11, 03:33 PM
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Join Date: Sep 2011
Location: usa
Posts: 2
Okay thanks. Hopefully I can figure it out.

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