On my 2002 mini cooper, manual, non turbo, I am getting the check engine light with a P0128 (coolant temperature below thermostat regulating temperature). From what I read the temperature must be around 90C. Last night I got into the tEEst menus and went to the 7.0 and 7.1, actual coolant and actual ouside temperature data. I assume both are reading in deg C.

recently I had to remove the bumper for a clutch fix and also had to unplug both temp sensors.

anyway the reading yesterday was as such:
From the normal left steering wheel gaugue I get 62F(16.67C) outside temp, with the tEEst menu 7.0 coolant temp is 92 while 7.1 outside temp is 218 fluctuating between 210 and 224. this morning gauge is 53F(11.67C), 7.0 is 13C at start up, 75 all the way to work and 80 while sitting in the parking lot. Very constant. 7.1 measured 164 at start up and 135 at the parking lot at work.

So I think
1) I need to replace the thermostat obviously
2) WTF is wrong with my outside temp sensor?????

from what I read, its a simple resistor type and it should range between -40 fully open when resistance is infinity and 122 fully closed when it is shorted. How come it reads past 122??? Do I have an ECU problem? can anyone help with this? I got to get this thing smogged soon. you know how that goes.

 

just a few minutes ago, I went outside and was able to remove the temp sensor behind the front bumper. Before doing so, I went to the tESt menu and set it to 7.1 outside temp. The ouside temp reading was 165. I went outside and removed the temp sensor. That made it jump to -40 on the side gauge and -400 on the 7.1 menu. I put in a 7.5Kohm resistor gave a reading of 168 on the 7.1 menu while the side gauge just went to -39 and very slowly to -38, -37 etc. I finally figured out what the heck was wrong with this reading. Its 16.8C! not 168C. So then my new conclusion is that I need a new thermostat and that both my temp sensors are correct and in working order. this is because the temp lingers around 75C, never getting to 90.5 to open the thermostat until all the coolant gets to that temp (after I get back home from work, starting at work with a somewhat warmer coolant).

 

I already replaced the thermostat with a normal OEM part, with an autozone proper part and with a chepo china part. Non worked for more than a few weeks. I keep getting an error 128 temp below thermostat control temperature. So I decided enough is enough there has got to be a better thermostat that controls at 195F. For a non charged mini 2002 that is... So I found this one thermostat in autozone. http://www.autozone.com/1/products/2...ast-15119.html not for 50 dollars or 35 dollars but 10 bucks. I brought it home, put it on the lathe to turn it down to the correct diameter, then put three notches for the clocking tabs on the silicone gasket. I would not fit on the plastic cap side because they have some protrusions so I dremelled those down. Finally it was in. I took for a ride. I noticed that the temp was not moving up for a while, but then when it hit "hot" middle point, it stayed there for a while. Then it opened, the temp dropped and slowly went up again never to come down. "hopefully!!!" I swear if it does, I either sell the car or I am going to take my sledge hammer and even out the fenders for a few hours.

If you are reading this forum, know that I really love the mini, but you must know that if you do not work on it, it is very expensive to fix things on it. Also it is a piece of crap in terms of all the hardware used and how thin the sheet metal is. Even the plastic pieces are cheap. Eventually the 4 piston engine makes the interior vibrate.... blah blah, not in a few years, probably in a few months. Again, it is a piece of crapola that I do not consider safe, but I love to drive. The problem is that I cannot possibly pass the smog test if the stupid check engine light keeps coming up because the engine is not hot enough. Done, I'm getting off my soap box for today. thanks for reading and enjoy your crapini's thermostat dilema. I might even get pissed off enough to make an electronic thermostat using an arduino and some irrigation/gas valve.

 

Ok so back to this stupid mini 2002. I got me a thermostat from another car that was available. I machined it down to fit the rubber piece and put it in the car. This is a brand new thermostat from autozone rated to 91C. I turn on the car and see it go to like 50C and it freaking stayed there for a very long time, going only to 75C after driving for 30 miles. Grr. pissed off, I chucked a piece of PVC, put a little 7/16" hole in it and made it fit the upper hose. started the car in the morning.... temp if I stay idle for a very very long time.. like 30 minutes, will go past 90C and make the stupid computer happy. However as soon as I drive, it goes to 70C or even less depending on the starting temp. So I got really smart this morning and took the hole and made it really small 1/4". temp stays at 80C. unless I idle for a long time, then the temp will climb to 105 and past, very very slowly.

What gives! why does the thermostat not work correctly?

My heater inside the cabin stays hot the whole time. Is there a water valve that is supposed to close but stays open?

The system is bleed and has plenty of coolant and heat comes out plenty fine ( heats up when/if engine heats up)

outside temp is 50C. This is every morning when I start that car, 50C.

I have not given up the sledge hammer temptation. I mean, it is literally 3 steps from the car when the car is parked next to my garage. I walk past it when I come into the house. I could just pick it up and give the car a few good swings. I really could do this!

 

I cut off the bypass plate, maybe that part made it too close to the cylinder thus causing it to activate too soon. I also changed the thermostat. Now it works fine. But I still will get rid of it if it passes smog.

 

I have a 2005 Cooper S that was getting P0128 error code. My scan tool shows it running at 166 degrees average. I changed the thermostat with a 195 degree unit and new coolant sensor. It still runs at the same temperature. Cooling fans seem to be running normally cycling on and off as they should. I have not tried to use an IR temperature sensor on the radiator tank or hoses to see what temperature they are showing. Any ideas?


Thanks,


Mark

 

Maybe a bad temp sensor. 13621486698

https://www.northamericanmotoring.co...mp-sensor.html

 

If it is running "cool" the fan should not be cycling on and off until it is up to temp....unless the a/c is on...and then it should STAY ON LOW, RUNNING ALMOST silently......
think you need to look deeper...your fan might be toast (low side blown), the thermostat could be bad, or installed backwards.....
The cooling systems on these cars are often neglected..folks force they have cast-iron blocks, a rare thing in modern cars, but with that fact comes EXTRA RADIATOR MX....

 

This is the second thermostat that we have tried. I put the first one in and it acted the same as before. I got a water temp sensor and figured as long as I had the thermostat housing off again I'd treat it to another thermostat incase I got a bad one. If the temperature sensor is bad it is bad in the exact same way as the one I removed. I find it unlikely that it is actually capable of running almost 40 degrees F lower than it should. I have been an auto mechanic on British cars for the past 28 years and I have not seen anything quite like this.

The thermostat cannot be installed backwards as the bulb part hits the housing. Plus it would have the opposite symptoms as the thermostat would not open when it should as the bulb is on the cold side of the system.

 

Did you replace the senor yet ?

 

I did replace the water temperature sensor. One interesting note. Since I changed the thermostat and temperature sensor a week ago I have not seen the P0128 ODBC code but the water temperature shown on the scan tool remains the same. It is almost like the ECU is displaying the incorrect water temperature to my scan tool. I am going to check the temperature at the thermostat housing with an IR temperature gauge next.

 

Yea, thats what i would do next. Does not make sensce unless the thermostat is really a cooler one. was it stamped or marked ( 11537596787 ) on the box?

 

Both thermostats I used were 195 degrees. The latest one was a Stant brand. The first one came with the thermostat housing so who knows what brand it was. I also made sure that the bleed hole on the thermostat was at the top as is normal practice.

 

ok, just wanted to double check. I guess you could have a bad connection at the sensor wire , but then it would not read any temp , and a CEL light would pop up. My guess is to check it with a IR temperature gauge next.

 

If your fans are operating normally, and the car isn't throwing a CEL for running cool I would unplug the scan tool and go on with life.

As long as there is coolant in the car and it is bled properly you should be fine, I've only replaced one or two temp sensors ever.

Has your fuel economy diminished since the work has been done? A car stuck in open loop will use more fuel than one achieving closed loop operation.

 

On the way home from work tonight I got a P0128 code again. Fuel milage is as it has been. 24 mpg average. 28 mpg highway. IR is next.

 

Hi,


Did you ever resolve this issue? I'm having the same problem. I got my car tuned not so long ago by RMW. But even before that my car was doing the same thing with and average engine temp of 160-180 and it ran even colder when in the highway, only thing the P0128 code never showed. I've changed my thermostat and my coolant sensor...still with no results, the code always comes back up.


I have a mini madness water 2 air intercooler, IDK if that has to do with anything keeping the engine temperatures too low.


Anyways, if you fixed it ever, what was the solution? I live in Orlando FL so the average temperature is very HOT outside.

 

No resolution. I have not gotten around to checking the temp with an infrared tester. I can reset the light, drive for a few hours and all is good. I can let it sit for an hour or two and be fine for awhile on the same drive and the light pops on. The temp on my ODB checker says 166 degrees F when I have a 189 degree thermostat. Somehow my thought is that the reading is not correct. It is warm here in Wisconsin now and I can't believe the fans are cooling it down that much. My Mini is completely stock.

 

I have exactly the same problem then, my temperatures vary from "165-180" degrees.

Does your air conditioner take time to get cold also? Trying to determine if the A/C gas pressure and level has to do anything with it.

I went ahead and did the resistor mod for the low speed fan. You should look into it, because sooner or later it might go bad.

What brand coolant sensor did you get?

When you get on the highway, your coolant temp gauge never gets to the middle either right? Unless you're standing in traffic.

 

Well I have done some more investigation and it does nothing to make the root cause clearer. I got an IR temp gauge. temperature at the head just above the thermostat housing is 160 to 168 degrees. The housing is about the same. hose coming out of the housing is about 160 degrees. Temperature further along the hose at the air bleed it 180 degrees. The passenger side radiator tank is 190 degrees. Drivers side tank is 120 degrees. Passenger side of radiator is very hot to the touch and the drivers side is comfortable. I was a classic car mechanic for 28 years and have never seen such a big temperature drop across a radiator. The temperature difference from the head to the tank (which doesnot make sense) could be because I am pointing the IR beam to different materials (Aluminum, rubber, plastic).


If the ambient air temperature is below 70 or 80 degrees the light will come on. Once you get in the 90's it will stay off.


Again, I have changed the thermostat twice including a new housing plus a new temperature sensor. I got the sensor off eBay so I do not know if there are some aftermarket ones that do not work correctly. Maybe it is reasonable to get an OE one from Mini and see if that changes anything. Or could it be a mucked up in the computer which a flash could resolve? Currently I am just driving it and paying no attention to the Service Engine Soon light. I clear the codes every so often to make sure that the P0128 code is the only one. Scan tool still shows the water temp to be 166 Degrees still. Temp gauge in the car just gets into the middle bold line.

 

Just a note in case others read this thread: don't try to correct a cooling problem by using a thermostat that opens at a different temperature than stock. You're just avoiding the problem.

 

I would agree. I have yet to see a car that will under normal circumstances rin 20 degrees below the thermostat temperature with the temperature sensor being directly next to the thermostat outlet. This really leads me to believe it is the sensor or what the computer is outputting to ODBI. If the sensor is telling the computer that it is running at 166 degrees instead of 189 degrees the computer is going to send bad data to the injectors and such. It think's it is colder than it is.

 

I'm still trying to figure it out. Seems to me that I also bought a sensor off of Ebay, but I think it works properly.


Have you had your car serviced at Mini recently? Did they flash the computer with any new firmware?


I recently had my car tuned by RMW. Before that the car still ran cold, but never gave me the service light and the code.


I went ahead and bought all OEM components to see if by any chance that helps, my fear is running the car too cold during winter time in FL.

 

The Mini has never been to a dealer since we bought it a few years ago. it has had the issue since we got it. I might try and take it in and see what they say. I also want to check to see if it has the dreaded cooling fan low speed resistor thing.


In the next few weeks I'm going to be replacing the lower A arm bushings with polyurethane ones as the current ones are wiped out. It also has the top strut mount broken rubber deal and mushroomed strut housing going on. Still drives well and I love it. 2005 with 87,000 miles

 

So, tomorrow I will be changing all the components. From what I've been reading, it could be the coolant sensor. But I'm not going to get my hopes up.


Like I said, I ordered everything OEM.


Markomatic, did you order this sensor?


http://www.ebay.com/itm/Engine-Coola...ZWecvM&vxp=mtr




This video is helpful too:




I'll try and find the wiring diagram to see if the signal from the ECM is constant.