Resolved my issue. Use OEM thermostat and coolant sensor. That is all. FIXED!

 

Well...I had the expansion tank split and after replacing it it seems the fooling fan was not coming on. Sooo I replaced the fan, thermostat, thermostat housing with an aluminum one and temperature sensor. Still runs at 166 degrees and the same error code gets set after running. This is the third thermostat and second temperature sensor along with the new fan and it's exactly the same as it was months ago. I'm not sure if I'm missing anything except maybe the firmware program is not right and needs a flash.

 

The first thermostat I bought was some "off brand" (Stant I think),and did not work, it came stuck from the supplier apparently. Then I went ahead and bought the OEM Temp sensor and OEM 195 degree thermostat and it worked like a charm, I've also heard people using Motorad thermostats with great success. I'm seriously thinking that Stant might have had a bad batch or something.

What brand of thermostat did you get? Also have in mind that Motorad sells 2 different thermostats too, 195 and 185 degrees. I know it sucks, but do try replacing with a new OEM thermostat if you haven't yet, or even try Motorad. I thought my problem was not the thermostat, and once I changed it to OEM, it resolved it.

 

The cooling fan seems to be functioning as expected since I changed it but still the coolant temperature is at 166 degrees from what the scan tool is saying and the CES light comes in with the same P0128 code. So to review, I have changed the thermostat three times, the coolant sensor twice, the expansion tank, thermostat housing and the fan unit. Still the car runs at 166 degrees and the light comes on just as it did from the beginning. If anything I would expect the car to run too hot not too cool. I am missing something here. I was a professional foreign car mechanic for 28 years and have owned a dozen classic Minis and two R-53's. I could just go on with my life but I hate having the CES light on even if I know why.

 

@ Markomatic - Did you install an OEM thermostat those three times or still buying/relying on aftermarket ? Sounds like to me like that stat is stuck open.

Even the aftermarket M7 180* stat never drops temps below 178*

 

The last thermostat and temperature sensor were OEM. When taking all of them out they were all closed since I was at ambient temperature. Somehow I find it implausible that all three are reading the same temperatures that are so much lower than what they are rated at. My feeling is that if I can get the temperature to me normal I will stop getting the CES code. 166 degrees is way to low for any car. It may take a trip to the dealer to see if there is something else going on. Could it be that the computer is outputting a lower temperature than is actually happening?

 

I had that problem with the aluminum thermostat housing and the thermostat that came with it. It worked ok for about a month and then got the low temp code. Changed the thermostat back to the previous stock one and all has been good. Didn't see any temperature marked on it when I removed it, but the stock thermostat was marked. It would only get about 2/3 of the way to the center mark on the temp gauge. Normally it gets to the center mark.

 

My temperature gauge runs right at the center mark

 

Get an OEM sensor !

The aftermarket sensors on eBay are crappola.

Got an ambient temp sensor off ebay last year. Was reading incorrect temp to dash computer.....went on Raman Noodle diet for three days and purchased a new one from MINI dealer.

 

Well this quote below was from post #13....it states it came with aluminum housing. MINI doesn't make one of those...from whom do you purchase your parts from ? eBay again ?? If so, stop doing that and get one through ECS Tuning....they get OEM parts direct from a MINI dealer close to them in IL.

 

Well, Finally success. After changing the temperature sensor three times, twice with OEM parts I am finally reading normal temperature and the Check Engine light is not coming on. I also changed the thermostat again with an OEM unit. I have used OEM thermostats the last 2 times. My feeling is that it was the temperature sensor all along as regardless of which thermostat I put in the water temperature still read 166 degrees. Again, One aftermarket sensor and two OEM. Regardless I am finally pleased to get that light off.


Now on to the trifecta lights.


Mark

 

I am getting the same code now 4 months and 2,500 miles after having the kit from ECS installed with the aluminum housing. No issues with warming up in the morning and the highest the gauge reads on the sport Chrono is the first line past 140.

I will probably toss the T-stat and pick up an OE one.

This was the kit I used .

https://www.ecstuning.com/b-hamburg-...37512733alk~h/

 

Ultimately my solution came after 4 temperature sensors, two of which were OEM. It has been a year and it has been no code and works as it should in hot or cold weather.

 

I am having the same issue now and getting the P0128 code.

I have replaced the coolant tank last year when it split, replaced the fan and resister after the old resister died, and replaced the thermostat and housing with a Beck Arnley unit, I think it's a 195F. Started getting the code and my temperature gauge (Chrono Pkg) shows about 80C, so I replaced the temp sensor with an Airtex Wells unit and cleared the code. It has not come back yet, but the temp gauge is still low and Torque app shows the temp in the 77 to 85C range.
Weird, I have a difficult time believing that the temp sensors are the issue since the replacement shows exactly the same temp. as the OEM one. Also my old thermostat looked fine, was closed at ambient and opened nicely in a hot pot of water.

The rad hose feels hot and so does the block and housing. The heater produces tons of hot air. I can blast the car up a long hill with the A/C on, warm day and the temperature never hits 90C.

I am thinking the DME is confused. Anybody have ideas?

 

I can be all wet here. But reading your chronology I cannot help but to wonder if you replace the OE thermostat and housing with aftermarket was the start of your problem. Changing too many parts without positive determination each is bad is never a good idea.

Lastly, DME seldom gets confused, unlike fallible human brain. I will add also the temperature sensor seldom fail in losing accuracy. They mostly fail catastrophically.

 

Could be. I replaced the housing and thermostat because the car was taking a long time to warm up, like 20 minutes or more of city driving and because it seems to be a common failure point. I was not getting a code though. Perhaps the new one is opening at a lower temp like 80C.


Next time I will use a genuine MINI thermostat.

 

The chrono package is not an accurate gauge. If you know someone with a scan tool that can see live data you can watch the sensor readout and see what is going on.

The factory thermostat opens slightly higher that 195 from the tests I've done and should maintain a running temp of roughly 200-215 deg. (93-101 C) depending on conditions. All the aftermarket ones I tested opened way too soon.

From the service manual:
Low speed fan kicks on at 221 deg. (105 C)
Low speed fan shuts off at 214 deg. (101 C)
High speed fan kicks on at 234 deg. (112 C)

I would put a factory thermostat in it and you'll probably find your issue solved.

 

Yeah could be the new T-stat, it's a Beck/arnley. I didn't think a T-stat was difficult to make so didn't worry about using aftermarket. It will be cheap and relatively easy to find out if it is the cause. I don't want to be like Markomatic and have to change each 3 times before getting a good part.


I have the Torque app and a BT OBD2 dongle, the coolant temp from that says the same thing as the Chrono gauge. I think both gauges are interpreting the same signal from the sensor.
I seem to recall that the low speed fan does come on before 90C on my car, I will test it out later.

 

The issue that I had was the same as yours. Bottom line was the coolant sensor was not reading correct making the ECU think it was running cool. I put in multiple thermostats and coolant sensors both OE and aftermarket but it remained the same until I hit on the last coolant sensor which solved the issue. Why it took so many to get one that seemed to work is beyond me. I was an auto mechanic for 25 years and none of this makes sense but it's been working for the past year +. Maybe a bad connection at the plug to the sensor and it took many on's and offs to clean it properly? Got me.

 

I had thought about the connector, but it doesn't seem likely because the signal is not erratic, just low. Next time in I will pull it, clean the connectors with DeOxit and tighten them up a bit.

 

CEL is back.

I don't think it is faulty temp sensor because this would mean a huge failure rate for the them. I will try a MINI t-stat and cleaning the connector on the sensor next.

 

Update:

CEL turned itself off and all the emissions checks show Ready. The temp still takes 15 mins to get to normal, but then stays at around 85C. So OK for now. Perhaps the DME needed some time to get used to the new sensor or it is just flakey?

Of course I bought a MINI thermostat, but maybe I can return it.

 

15 min to get to normal is longer than spec, I would still put the Mini thermostat in.

 

Put in new t-stat. Tested on stove with candy thermometer first, oem opens at about 90C old one opens at about 84C. Hopefully the CEL will go away.

 

Picked up a new Thermostat from the dealer and all is good now :-)