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Discussion Starter #1
Figures I finally get around to cleaning up the focus, spent all day on it and the next day the check engine lamp comes on heading to work..... Pulled a PO128 code which is a low coolant temp reading. Everything is checking out fine so I imagine it's the sensor. But compared to my last vehicle (a 92' ranger) the duratec is COVERED in sensors and I thought it had to dang many. So can anybody tell me where the coolant temp sensor is? Or excuse me the Engine Coolant Temperature Sensor (ECT) It's nowhere I expected it to be so I'm confused? Appreciate any help! Including if you know something about this code that I don't know[thumb]
 

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The Duratec uses a Cyl. Head Temp. sensor if I remember correctly. It's located between spark plugs 2 and 3. BUT.......if your coolant level is in the ball park then I'll bet your thermostat is kaput. It is not fully closing and the coolant temp is not getting "up to temp" (not sure of the exact temp., but is usually around 170 to 180 deg. F) quickly enough, and the ECM is setting the P0128.
 

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92 Ranger = not Duratec. Those engines didn't appear until 03. Back in 92 you had OBD1 engine controls which used one sensor for gauges, and another sensor for computer input. That caused a few more sensors than are used now on OBD2 systems where you have one sensor that is for the computer, and the computer sends a signal to the gauges.

I would see if someone has a infrared thermometer where you can check the temperature of the radiator, engine block, and upper radiator hose before you dive into a thermostat job on this car. There is also a way to double check the sensor's readings with the electronic odometer. Key off, press and hold the trip odo reset button, turn key on, continue to hold reset button until the odometer reads [test], now each time you press and release the odo reset button you scroll through one of 30 test functions. It will remain in test mode until you turn the key off. You need to look for the one that reads [40 C] or whatever your temperature should be in C at the time. If the car has cooled overnight, then it's likely to be close to ambient temp. If it has not cooled, expect a higher reading. Drive the car in test mode. You should see your engine temp rise to about 95C, then drop down to 80 or so as the thermostat opens. This cycle will continue several times before the engine temp settles above the thermostat temperature of 92C. You should compare your findings with the test mode with those of the infrared thermometer under the hood. I would expect a 10% difference even if things are working right. More than that could be indicative of a problem with the sensor.

You should also check the sensor wiring, and if you are in test mode and you see sudden jumps or drops in temp to 0 or some ridiculously high temp like 200C, then you know there is a problem with the sensor itself.

The thermostat in this car is not a simple task to replace, so that's why I recommend methods of diagnostics first to be sure that the thermostat is what is failed. With a failed thermostat you won't see the cycling of temperature as I wrote about above. The temp will simply slowly climb up.

If you decide that you want to just replace the thermostat, you'll need an intake manifold gasket, and the correct thermostat. You need an inspection mirror to verify whether or not you have a thermostat with a supplemental sensor built into it. The thermostat is located under the intake manifold on the right side of the engine near cyl 1. Follow the lower radiator hose up to the block, and that plastic doomaflatchie is the thermostat. It is built into the housing. Look online at a retailer with pictures like Rock Auto.com, and you'll see what you should be looking for. If you see anything electrical that plugs into the thermostat housing, then you need the more expensive thermostat. I would also suggest purchasing the lower radiator hose whether you need it or not, and a new PCV hose whether you need it or not because those are not expensive and you need to remove the intake manifold to replace those also.

You will experience sticker shock when you see the price on this thermostat- even from a low priced retailer like Rock Auto. I shudder to think what Autozone is charging for this thermostat. To give you perspective, you can purchase your own infrared thermometer for much less than you can purchase even the cheap version of this thermostat that doesn't have a sensor built into it.
 

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Nevermind, I just checked, Autozone and Rock Auto have similar prices on these parts. RA was $125 for the one with the sensor, and $20 without sensor. The Zone wants $150 and $27 respectively. Shipping would make the cheaper one more expensive to purchase from RA unless your sales tax is high. I already know that intake manifold gaskets are similarly priced- about $25. I don't know about PCV lines or the valve itself.

There, now you don't have to have sticker shock at least not later. Hopefully you don't have the sensor.
 

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Discussion Starter #5
Thanks for the info. I had no idea there was a way to test from the display I'll be checking that out tomorrow. I checked with the infrared and it's running normal, nothing seems to be off so I'm thinking it's the sensor. But either way I have the tstat housing without the extra sensor so glad it's not holy crap expensive when that time comes. On an interesting note I reset the computer to hide/clear the light and it hasn't come back on since? Which is random whether it was the sensor or the tstat..... I will be playing with that nifty feature I had no idea existed tomorrow thanks whynothtinkwhynot!

Oh but what I meant was the Ranger had WAY fewer sensors not to mention easier to trace systems than the focus does. Maybe it's because I've never had a FWD so it's all discombobulated to me but wow is it confusing
 

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... You need to look for the one that reads [40 C] or whatever your temperature should be in C at the time. If the car has cooled overnight, then it's likely to be close to ambient temp. If it has not cooled, expect a higher reading. Drive the car in test mode. You should see your engine temp rise to about 95C, then drop down to 80 or so as the thermostat opens. This cycle will continue several times before the engine temp settles above the thermostat temperature of 92C. You should compare your findings with the test mode with those of the infrared thermometer under the hood. I would expect a 10% difference even if things are working right. More than that could be indicative of a problem with the sensor. ...
Thanks for the great information, whynotthinkwhynot. So... let's say I've driven around in test mode and the temperature reading hasn't gone past 67 C. But my temperature gauge needle is directly in the middle, and I have plenty of heat coming out of the vents.

Ideas?
 

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Are you still answering questions on the ford focus temp sensors?

Nevermind, I just checked, Autozone and Rock Auto have similar prices on these parts. RA was $125 for the one with the sensor, and $20 without sensor. The Zone wants $150 and $27 respectively. Shipping would make the cheaper one more expensive to purchase from RA unless your sales tax is high. I already know that intake manifold gaskets are similarly priced- about $25. I don't know about PCV lines or the valve itself.

There, now you don't have to have sticker shock at least not later. Hopefully you don't have the sensor.
Hey are you still on message board?
 

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Hey are you still on message board?
He (whynot) is occasionally here. I have not seen him recently.

What is your question? Maybe someone else can help you.

BTW I have never seen a Focus with a T-stat that has a temp sensor on it. The (older) cars are simply not wired for it. I have asked & challenged other members previously about this. I am unsure about 2008 and newer cars... but again, I have yet to see/hear of a Focus "with sensor" on the T-stat.
 

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In my case, it was a bad thermostat, which is a common problem in these cars. They are kind of an SOB to change too.

I plugged my code reader in and drove it so I could monitor real-time data. I was running (at most) 170 degrees. My temp gauge was in the middle and I had reasonably good heat. The car would run at fast idle when I came to a stop. Pretty noticeable with a manual trans.

Changed out the thermostat and now it's back to normal (high 180's to low 190's) . It's nice not having my car on fast idle all the time. My temp gauge still sits right in the middle, which struck me as odd, but that's the fact. I have more heat from the vents now though.
 

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The temp gauges are NOT linear like in days past, they stay in one spot pretty much from barely warm to almost 100% overheating. The needle is highly damped to do that to reduce complaints by fussy people, it saves millions in warranty costs. That way all of the cars run 'in the middle' and life is good..........to the uninformed. It works great in a Trump world.

Now you know why.
 

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In my case, it was a bad thermostat, which is a common problem in these cars. They are kind of an SOB to change too.

I plugged my code reader in and drove it so I could monitor real-time data. I was running (at most) 170 degrees. My temp gauge was in the middle and I had reasonably good heat. The car would run at fast idle when I came to a stop. Pretty noticeable with a manual trans.

Changed out the thermostat and now it's back to normal (high 180's to low 190's) . It's nice not having my car on fast idle all the time. My temp gauge still sits right in the middle, which struck me as odd, but that's the fact. I have more heat from the vents now though.
Fourspeed,
Ive got my new Motorcraft thermostat/housing ready to install on my 2005. I know you (and others) have noted that the job is a PITA. Several 'how-to' videos recommend at least partially removing the PS pump. Since you just recently did yours can you outline what steps you took during your thermostat R/R and/or provide any insights?

Thanks
Paul
 

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Fourspeed,
Ive got my new Motorcraft thermostat/housing ready to install on my 2005. I know you (and others) have noted that the job is a PITA. Several 'how-to' videos recommend at least partially removing the PS pump. Since you just recently did yours can you outline what steps you took during your thermostat R/R and/or provide any insights?

Thanks
Paul
Sure. My disclaimers: I do not claim that my way is the best way, or even a good way. No guarantees.

*I removed the plastic pan thing in back of the bumper.
*Pulled apart two electrical connectors at the top driver's side of the fan assembly.
From underneath, used my thumbs to open up the two top fan mounts, then pushed the fan assembly up and out of the mounts. It comes out the bottom pretty easily. This gives you some more room to work, and that is badly needed.
*Drain the radiator. Even so, you'll get some coolant dumping out when you remove the thermostat.
*I was going to follow a video where the guy got to the thermostat housing from above without removing the power steering pump. That seemed darn near impossible, so I decided to remove the P/S pump. Got the top two bolts out, which makes the reservoir loose. The pump is held on with two more bolts that are tough to access. I popped the reservoir off and got a finger over the hole ASAP. Still made a big mess. Next time, I would try to drain it first using the return line. Taking the reservoir off seemed to give me enough room, so I did not remove the pump itself.
*I unplugged two electrical connectors that were in the way.
*Now you can use a 1/4 drive, extension and socket to get to the thermostat bolts. Shine a flashlight down the gaps in the intake manifold and you can see the bolt enough to tell when you get the socket on it. Pull the three bolts and pull the thermostat housing out enough to get at the hoses.
*I removed one hose from the thermostat housing, the one that goes to "I forget what" on the driver's side of the engine. I left the rest of the hoses in place. I took the lower radiator hose off the radiator, and the coolant reservoir hose off at the coolant reservoir.
*I dropped the thermostat housing and hoses out the bottom of the car.
*I marked the hose locations with a Sharpie, then moved the hoses to the new thermostat housing keeping orientation the same.
*Then I put it all back together in reverse, filled the power steering reservoir, filled the coolant and ran the car for a while on the jack stands looking for leaks. I had no leaks and no problems with air pockets that I can tell.

I still need to change the coolant and I plan to get a vacuum device for that. I didn't have the tool or the good coolant on hand, so that job will have to wait.
 

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Sure. My disclaimers: I do not claim that my way is the best way, or even a good way. No guarantees.

*I removed the plastic pan thing in back of the bumper.
*Pulled apart two electrical connectors at the top driver's side of the fan assembly.
From underneath, used my thumbs to open up the two top fan mounts, then pushed the fan assembly up and out of the mounts. It comes out the bottom pretty easily. This gives you some more room to work, and that is badly needed.
*Drain the radiator. Even so, you'll get some coolant dumping out when you remove the thermostat.
*I was going to follow a video where the guy got to the thermostat housing from above without removing the power steering pump. That seemed darn near impossible, so I decided to remove the P/S pump. Got the top two bolts out, which makes the reservoir loose. The pump is held on with two more bolts that are tough to access. I popped the reservoir off and got a finger over the hole ASAP. Still made a big mess. Next time, I would try to drain it first using the return line. Taking the reservoir off seemed to give me enough room, so I did not remove the pump itself.
*I unplugged two electrical connectors that were in the way.
*Now you can use a 1/4 drive, extension and socket to get to the thermostat bolts. Shine a flashlight down the gaps in the intake manifold and you can see the bolt enough to tell when you get the socket on it. Pull the three bolts and pull the thermostat housing out enough to get at the hoses.
*I removed one hose from the thermostat housing, the one that goes to "I forget what" on the driver's side of the engine. I left the rest of the hoses in place. I took the lower radiator hose off the radiator, and the coolant reservoir hose off at the coolant reservoir.
*I dropped the thermostat housing and hoses out the bottom of the car.
*I marked the hose locations with a Sharpie, then moved the hoses to the new thermostat housing keeping orientation the same.
*Then I put it all back together in reverse, filled the power steering reservoir, filled the coolant and ran the car for a while on the jack stands looking for leaks. I had no leaks and no problems with air pockets that I can tell.

I still need to change the coolant and I plan to get a vacuum device for that. I didn't have the tool or the good coolant on hand, so that job will have to wait.
Thanks for the quick reply! My 2005 is slightly different in that the PS pump reservoir is not mounted to the pump itself. Other then that I believe everything else to be the same (or very similar).

Also curious what brand/part number thermostat/housing did you use?

Thanks again
Paul
 

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FWIW

I used a Motorad 512-185 Thermostat.

Also, the R&R method I used was different. I removed the intake manifold (to replace the PCV Hose) and replaced the T-stat while the intake manifold was removed.

I have never replaced the T-stat using the method you (Fourspeed) described.

While that method may be easier and less time, I still prefer the other method (removing the IM). Old dog verses new trick? Maybe so.
 

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Not sure if this thread is old and dead but....

First time I have learned about the road test option... I definitely will try this, as my temp gage is as random as a dice roll...

I have a question regarding this though... If just the gage has failed, will the test mode read correct? I assume yes.

And I also assume that if the sensor has failed the test mode will not read properly.

In effect telling me I'm either wrenching under the hood, or taking the cluster out...

Hope the thread isn't dead because in the next day or 2 I am replacing the failed PCV Hose so it would be a good time to know about the Thermostat.
 
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