I mistype'd the subject line - this is regarding P0128 (Coolant Temperature Below Thermostat Regulating Temperature), and NOT P0218...

Last week (Monday) my temp icon showed up on the tach display. Fortunately, I was very close to the MINI dealer so I pulled in for a diagnosis (was about 30 minutes from home). It had a slow coolant leak which they topped off and told me to keep an eye on it since I wasn't prepared to fork out $650.

I replaced the thermostat myself two days later (Wednesday).

The following morning (Thursday...) I got a C.E.L. so I limped in to the MINI dealer again. They said I did a great job on the thermostat but swapped two temp sensor plugs. After the $119 diagnostic fee, they cleared the code and all was fine until either Sunday night or Monday morning (I'd probably driven at least 100 miles by this time).

My wife drove the car Sunday, but she said she never noticed the C.E.L. and she was actually looking for it because the car felt funny (unresponsive) to her. She didn't have the sport button pushed... I was following her, and I know for a fact the car was responding fine as I had a hard time keeping up with her in our minivan.

The following day (Monday) I got in the car, started it, and noticed the C.E.L. stayed on. It's been on continuously since then. Autozone said it's showing P0128 (Coolant Temperature Below Thermostat Regulating Temperature). The car was cold (but only about 65-70 degrees in my garage). I don't think this code would show up immediately after a cold start, as it requires a specified amount of time to reach the proper temperature before it would recognize a fault. So, it's possible it came on the previous night while my wife was driving it and she just didn't notice it...

So, that's where I'm at. C.E.L. is still on, and I'm debating taking it to the MINI dealer on my way home to let them diagnose it again (another $119).

For the last few weeks, It's had a rough idle for a few seconds after a cold start. I don't touch the throttle or anything - it clears up after maybe 10 seconds. I back out of my driveway, put it in D, and it stumbles a tad but runs perfectly fine a few seconds later and I never have the problem again until the next 'cold' start (I live in Texas). It's never stalled on me, but it has stalled on my wife twice - turns out she starts the car and immediately puts it in gear - I told her that's not good for the car and to please stop doing that...

Now that I think about it, the car randomly was hard to start one morning - it turned over for maybe 10 seconds before starting... It hasn't done that since then.

I run Lucas fuel system cleaner through the tank every couple of months (the current tank has the cleaner in it), and I did the seafoam treatment a couple months back as well.

I replaced the plugs a few months back as well.

Any suggestions before I take the car back to the dealer and pay for another diagnostic fee...?

It's a 2008 Cooper S with 80k miles - bone stock.

 

* MINI DTC P0128 (0x2F07) - Coolant Temperature Below Thermostat Regulating Temperaure
* MINI DTC P0128 (0x348A) - Program Map Thermostat: Sticking in Open Position

Your hard starts and stumbling are from the Coolant Temperature Sensor (CTS) in conjunction with stuck-open thermostat condition.
When you replace the t-stat, did you use OEM parts? Remember, it's electronically control and not mechanically operated.

People have had your similar situation and it's been either a CTS or a thermostat.
Search the archives and you'll see what others have done.

- Erik

 

I replaced the thermostat housing and coolant with OEM parts directly from MINI's part's department.

I took my MINI in for diagnostics yesterday for the CEL. Turns out my P0218 must have been an old code that hadn't cleared yet, as nothing related came up during their diagnostic scan yesterday. I suppose it's possible I had too concentrated of a coolant mixture in the system at one point, and I know the coolant level got too low at one point while I was trying to refill the system.

That being said, it appears I had a new code that I wasn't aware of since the light never turned off. It seems that my most recent seafoam treatment knocked a chunk of carbon loose and it resulted in multiple misfires and it also showed that unmetered air entered the system (from my seafoam treatment?). That's all that showed up on the diagnostic. They performed the fuel induction service to flush out the crud and kept it overnight for a cold start test. Hope to have it back around noon today in plenty of time to take my boy camping for the weekend!

The service adviser recommended doing the flush every 30k miles and using their Crud-B-Gone or other similar products through the gas tank. He also suggested I replace the spark plugs "because they'll probably foul out soon because of the seafoam treatments", even though I just changed them about 5k miles ago...

 

Okay - just got off the phone with my service adviser. After the cold starts today, the car was still throwing CEL's pointing to two things - one being the High Pressure Fuel Pump which they are replacing under the 100k/5yr extended warranty, and the other looks to be either a faulty thermostat (bad part since I just replaced it) or a bad install on my part - guess there is no way to tell at this point. Fortunately they are covering the thermostat under the part's warranty, so I just have to pay for labor to install another one.

 

Am I reading this right, a P0218? And not a P0128?
You've type the code differently now twice... just making sure I referenced the right one for archiving purposes.

- Erik

 

Sorry - yes, P0128 was the actual code.