"Normal" Temp Gauge Position/Movement

[acturner]

Has anyone else noticed their temp gauge moving around slightly?

 

History: driving home the other day and CEL comes on. Car is running fine, no hesitation, no coughing, gauges look good, no other warning lights. So I don't worry about it. I get home and pull out my scan tool. Trouble Code P0128, ECT below Themostatic control. Hmmm, maybe thermostat has failed. I do some searches on this forum and convince myself that this is the issue. Not a problem, I'll order a thermostat and I'll change it when I get the time.

 

Since then, I've been watching the temp gauge while I'm driving (of course I never really paid that much attention to it before) and I notice it moves around way more than I thought. Driving around town and cruising down the highway the needle on the temp gauge almost covers the little themometer symbol and sits there, so the engine gets up to temp ok (this goes against the idea that the thermostat is stuck open). If I step on the gas pedal to accelerate quickly, pass another car, etc, the trans downshifts, RPMs go up, speed increases and I can watch the temp gauge go down slightly. Messing around last night I shifted to L-range and held the RPMS at 4000 going 70mph on the interstate for approx 20 to 30 seconds (so water pump is moving lots of coolant and lots of cool air going through rad), the temp gauge dropped from the middle point covering the thermometer to the edge of the wavy lines on the gauge. It never went any lower, so it never dropped all the way to the "C" mark. Now I'm wondering, does the edge of the wavy lines represent the termostatic control limit (ie my thermostat is fine and works as normal) or possibly just the limit of the cooling capability of the ambient air passing through the radiator last night?

 

It does seems like the car takes a bit longer to heat up than before, but again I never really paid to much attention to it before the CEL came on.

 

I will try to borrow a scan tool with real-time data to see what the ECT is as the gauge moves around. This may tell me if the thermostat is OK or not. Does anyone know what the ECT control temp is (165, 175, 185degF)?

 

Thanks for the input.

[dbrooks]

Oh brother, does this sound familiar. I just went through this problem with my 06 Fusion SEL with I4 engine.

 

I have had the code you mention on and off for months. First changed the sensor, no help, same issue. I dreadred changing the thermostat becuase it's a real bear on this engine, took me and a helper 3 hours. WOW.

 

I think the issue is definately the Thermostat, I didn't want to believe it. The temp gauge in my experience should point nearly straight up, i.e. in the middle of the range between C and H. Prior to changing the T-stat my gauge pointed slightly more towards cool, never staright up. I have put a temp meter on it since changing the T-stat and now the temp seems to center on about 223degF plus/minus 3degF. This really seems high to me but this has kept the CEL off, since, and one thing I noticed right away was how much quicker the temp gauge reached the operating temerature.

 

I am still trying to determine if this temp is optimal, but checking some performace parameters post new T-stat. Will update this post if anythng significant changes.

 

Good luck.

 

DB

[Dyoct]

Oh brother, does this sound familiar. I just went through this problem with my 06 Fusion SEL with I4 engine.

 

I have had the code you mention on and off for months. First changed the sensor, no help, same issue. I dreadred changing the thermostat becuase it's a real bear on this engine, took me and a helper 3 hours. WOW.

 

I think the issue is definately the Thermostat, I didn't want to believe it. The temp gauge in my experience should point nearly straight up, i.e. in the middle of the range between C and H. Prior to changing the T-stat my gauge pointed slightly more towards cool, never staright up. I have put a temp meter on it since changing the T-stat and now the temp seems to center on about 223degF plus/minus 3degF. This really seems high to me but this has kept the CEL off, since, and one thing I noticed right away was how much quicker the temp gauge reached the operating temerature.

 

I am still trying to determine if this temp is optimal, but checking some performace parameters post new T-stat. Will update this post if anythng significant changes.

 

Good luck.

 

DB

 

Wow, the temps are into the 220 range after the repair? I've had the low temp code on and off for some time. During the summer and with the AC on the temp would never get past much 190 but it would vary from like mid 160s to the 180s for the most part. On cool mornings if I had the AC compressor running, I would see the temp gauge needle maybe go a 1/4 up and after a few miles the CEL would come on. I have the thermostat and I have already drained the original coolant, flushed with water, added a flush and water mixture and then flushed with water again and I am dreading to tackle this project.

[FusionDiffusion]

I have put a temp meter on it since changing the T-stat and now the temp seems to center on about 223degF plus/minus 3degF.

Your temp gauge must not be all that accurate or is improperly placed (like in an air void). Anything over 220ºF is overheating in my book. Ideally the water temp should be between 190ºF and 200ºF for optimal emissions and fuel economy. Less than 180ºF and your fuel economy will suffer.

 

It sounds like your fixed your problem though. The factory gauge should be pretty much straight up and shouldn't really move at all. You could hook up an OBD II reader that reads live data (e.g. ScanGauge) and keep an eye on your coolant temps that way if you didn't want to install a separate gauge.

[Dyoct]

220 range just may be normal for these engines....

 

I bailed on the T-stat replacement after I couldn't unsuccessfully get it out. During my trip up north for Thanksgiving I saw the temp gauge stop right before the icon. The next day the CEL came on. I checked the data with my scanner, coolant was 172degrees on the highway with ambient temp no higher than 40degrees. Idling it got up to 180. I decided to redneck engineer the car and block off the radiator with cardboard. No change in temperature reading. I disconnected the fan, let the car idle for 15 minutes and temps got up to 228. Once moving, the coolant dropped to about 178. Mileage was never above 28mpg on the entire trip from Georgia to Michigan and back.

 

The other night I get the idea to just use packing grade plastic and wrap up the front end blocking any airfolow off. That did the trick, the temps were hovering at 221 on the freeway, up to 230 idling. I ran the vehicle up to Indianapolis, 40MPG at 55mph for 30 minutes. 30MPG at 100mph for 15 minutes. Temps stayed at 220 range. Although, on the way back down, in the mountains in Tennessee the temp got up to 246 and I saw the needle more towards the right for the first time ever but it did not even touch the red zone. I ran the heater on with defrost and laid off the gas and temps got back down to 220. Overall mileage for the trip 32.3mpg.

 

If you see a black Fusion with a Michigan plate rolling around A town with the front end all covered up, that's me.

 

Oh, and oddest side affect. While the scanner shows outside temp of 100degrees with the front end blocked off the EATC shows 130+ degrees!

[FusionDiffusion]

Yes, there might be some error in the temperature probe. Just be sure you have all the air out of the system. Personally I would never cover up 100% of the radiator openings. Being too cold will just hurt your fuel economy, but being too hot will warp you cylinder heads and cause your head gasket to leak. One will end up costing you much more in the long run. Running at some of those higher temps are just risky. If you suddenly loose cooling system pressure (hose or cap leak) at those temps the coolant will flash boil. At the least you will have coolant everywhere and be stranded on the side of the road. At the worst your engine is toast in the middle of nowhere. I implore you to leave at least 25-50 square inches of grill open as a precaution. Keep an eagle eye on that temp gauge. Anything past 3/4 on the gauge and I would be very concerned.

 

The temps are measured in different places. The climate control temp is measured in the bottom of the radiator. The scanner shows the intake air temp measured near the air box. Your radiator blockage has had the effect of raising the intake air temp, which will lower fuel economy slightly.

 

It's your car so you can do what you want. Personally I would just pay to have the thermostat housing professionally replaced since it is cheaper to fix than an overheated engine.

 

P.S. Do not run the defrost if your engine is overheating. Defrost engages the A/C which will pump more heat into the engine bay. Run the heat on full hot and max blower on the feet, panel, or bi-level settings only (no recirc either). Open your windows if you get too hot. If the gauge is even close to the red zone, you need to pull over, open the hood, and run the heater full blast while idling until the gauge gets back to 1/2.

Edited December 7, 2011 by FusionDiffusion