Drain all coolant to replace coolant temperature sensor?

[Hadrien]

First off I will start with what I have:

1992 MX-3 1.6L 4CYL with 5SP Transmission

Uber basic transportation to and from work, that's all. I'm just hoping to make it a bit more reliable after recent events.

Few days ago the car would not want to start without giving it alot of gas after it had been on for awhile (5 mile commute to work). So I got on here and did a little research, everyone recommended that a tune up was in order and that it could be a clogged fuel filter. So new plugs, wires, and fuel filter went in this last weekend.

I wasn't fully expecting it would fix it, but hoped. Same thing happened (car starts fine first thing, but struggles after that) the last 3 days randomly, but its easier to get going now after cranking on it for 15 seconds or so.

Got a CEL this morning on the way to work, so I did the paper clip thing in the diag bay and got a code 9 - Water Thermosensor Error. I see that the Coolant Temperature Sensor is only like $15 at Auto Zone and Advance Auto Parts.

Before I went and bought it though I read through the MX-3 online manual here and saw that they recommend draining all of the coolant before replacing the sensor. I was wondering if I truly have to drain the coolant or if I could just swap the sensor out while the engine is cold with the radiator cap off?

Any advice would be much appreciated. I'm not against draining the coolant, but time is limited for me this weekend (weekend shift) and the sensor replacement looks like a 5-10min job at best. Thanks in advance.

-Hadrien

[Mi|<E]

Put a couple paper towels under the existing sensor and unscrew it. Screw in the
new sensor fairly quickly and you wont loose much coolant at all (maybe an ounce or
two if your fast). Make sure not to overtighten it.

Test your coolant and if it checks out dont worry about draining it.

PS - dont let animals near spilled ethylene glycol (coolant) cause its sweet and they
love to lick it up. If it does by chance happen like a cat or a dog gets into
it then get them drunk with good ol Ethyl Alcohol (vodka or tequila work best).

[Hadrien]

Should I run the car with the radiator cap off for a bit once I do that to allow any air bubbles out?

[Mi|<E]

If your worried about air bubbles it wouldn't hurt to do that. Park it with
the radiator cap at the highest point and let it idle to temperature, filling
with new coolant if it falls below cap level.

[Hadrien]

Excellent, thanks for the answer Mike!

I will give it a shot this weekend.

[shameem]

There are 3 coolant sensors for the SOHC - the one connected to ECU is right next to #1 injector. Make sure you purchase and replace the correct one....

[Hadrien]

Hmmm injector #1? The one I am looking at is right by the thermostat. That is the one that shows in the online manual that is posted here. It is close to a spark plug well.

I was going to replace the one that I circled in red in the pic below:

[mudflap13]

no it is not the one that controles the fuel mixture is the thermo sensor (the one that thats behind the no1 injector) when it goes bad it wont like to fiire up mine wass the case after me rebiuld it would crank up ant run fine but after it warmed up and i turned it off and then try to restart it wouldnt and i just had the header on and it smeeled real rich and i wouldnt have noticed it had i not had just the header on and after some poken and proding this site and my manual i descided to look at it wendt to remove it and it disentigrated and then went back to my manual to get the resistance values for it so i knew i had a busted alarm clock layin around so i took all the resisters out of it then found one with a reusable resistance value so thats what in using till i get some time to change it out of course the ecm thinks the car is at a constant 215 degrees F but i have no broblem starting up when its warm

[mudflap13]

ill post a pic tomorrow and give the values and such when i get a few minutes and its not raining horses and elephants lol

[Hadrien]

Thanks mudflap! Is it the same part number as the one that I outlined in the picture? I guess I am trying to ask if they use the same sensor in all 3 places or is each sensor different?

[Daninski]

Sorry read thorugh this post quickly. Fill your coolant, install the cap and then squeeze the lower radiator hose. This will evacuate any air from the system. Running the engine with the cap off will just cause the system to overflow. IMO I did an engine install and I kept aggressiveely squeezing the lower rad hose (while removing the cap and checking the coolant level) My engine started and ran with no coolant issues. Keep the temp to hot on your dash.

[mudflap13]

no totally different numbers and parts

the part u need is
Part No. WT5000 $14.99

the number for the temp guage sensor is TS26991 in front of the head next to the header
and the one for the fans next to the thermostat is Part No.WT653


these are advance auto parts numbers i used to work there i got most of the numbers and prices memorised worked ther for about a year till cut backs 3 months ago

[mudflap13]

its the one with the square plug probably green like mine unless its still got the rubber cover still on it

[Hadrien]

no totally different numbers and parts

the part u need is
Part No. WT5000 $14.99

the number for the temp guage sensor is TS26991 in front of the head next to the header
and the one for the fans next to the thermostat is Part No.WT653


these are advance auto parts numbers i used to work there i got most of the numbers and prices memorised worked ther for about a year till cut backs 3 months ago

Cool, glad I asked here first, the Chiltons manual and the Workshop manual had nothing about 3 sensors.

I will have to look at the car later today to see if I can find the one you are talking about, at least it's the cheapest one

-Hadrien

[Spotted]

Does the 94 1.6 DOHC have 3 sensors also? I know there are at least 2 a temp sensor and a temp sender is there a thermothingy for it also?