Hello Everyone!

Hoping to get some assistance with a persistent issue I've been having with my R56 justa. Its a 2011 manual transmission with ~45k miles on the engine. I live near DC, so the temps have ranged from 30-50*F since the issue first arose.

Sometime last week on my way to work I was prompted with a yellow check engine light. Pulled over, checked the oil, coolant, and restarted the car. Both oil and coolant were low. After cycling the ignition the check engine light went away however and the car drove as normal. When I got home I topped off the oil and coolant, I was a quart low on oil and had just done an oil change 1k miles prior. No oil leaks on the drain pan or on the ground at any point before that or after.

Drove very little over the next few days but on my way to work one day it came back on. The car started running very poorly, loss of power and all. The light wasn't blinking, so I don't think I was in limp mode. Parked it at home and stopped driving it. I noticed that the high speed radiator fan stayed on for ~5 minutes after shutting off the ignition. Came back hours later (engine was dead cold) and ran the car for less than 20 seconds, the fan kicked on and stayed on for another 5 minutes after shutting off the ignition.

I pulled the code and was prompted with P0128. "Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature" So the fan staying on made me think that the coolant temperature sensor was malfunctioning, along with the thermostat error code and some diligent research/advice, I decided that the thermostat and housing needed to be replaced.

I replaced that yesterday, which included a new temp sensor along with the thermostat, and the wiring adapter from the two sensors on the housing to the wiring harness. The issue persists however, there was no change to the fan issue, check engine light, error code, or drivability. I believe the car is running poorly under load because the ECU is dumping more fuel into the cylinders in order to compensate for the low temps. It idles fine under no load. Thats just my guess though...

My battery has run down as a result of the fan drawing power when the car is off, being six years old, its probably due for a replacement anyway. That said, prior to these issues, its never given me even a hint of a problem, so I don't think low voltage to the ECU is the culprit. I'd like to find the source of the problem before replacing that however.

At this point I'm thinking its one of two things, but one wouldn't explain the OBD2 code. I think my radiator fan relay may be the cause of the fan issue, not entirely sure on that but I've read enough to know that its a known issue. The only other possibility I can think of is that there's a fault in my ECU that's throwing the code, or a faulty lead somewhere in harness between the thermostat and ECU that's causing the car to think the thermostat is stuck open...

At this point I'm looking for some advice. Not really sure where else to go from here, but I'm currently not driving the car because I would rather not damage the engine with the temps not being regulated properly. I have yet to take it to a dealer, because I don't fully trust my local Mini dealer and because I'd like to avoid paying out the wazoo for diagnostics. Though that may be my only option if nobody has any other thoughts on the matter...

Thanks in advance for your help everyone!

 

A weak battery can cause all kinds of havoc on our MINI's. I would say replace the battery, and go from there. I remember an issue with Hondas back in the early-mid 90's where a weak battery would cause the radiator cooling fan to come on in low voltage situations, and that running fan would completely drain the battery. Odd, but it happened. Many times.

 

Replaced the battery this evening. Still no change.

A couple of other notable data points. I took the car around the neighborhood to see if that would clear the code last night, there's a noticeable rattle coming from what sounds like the passenger side of the engine while lugging at a higher gear than appropriate. Its even slightly noticeable when pulling away from a stop in first, more so however when driving the car up a slight incline one gear higher than appropriate. The water pump is on the passenger side of the engine, no? (I guess the timing chain is also on that side.... Hmm. Lets hope that's not the issue. The car idles just fine and doesn't seem to have skipped a tooth, yet.)

Also, I noticed that the driver side window will retract when opening the door, but fails to return up when the door has been closed. I suspected that this was a result of the battery being low from the drain of the fan, however the issue persists after replacing the battery. Perhaps this, along with the persistent P0128 code are telling me that there's and issue with the ECU itself. Though I'm not sure if that controls the window relays. Is there any way to do a factory reset to the ECU without taking it to the dealer? Any specific OBDII scanner that would be worth my time/money?

The only other suggestion I've been given is to borrow a coolant pressure tester from advanced auto to make sure that I don't have a leak in the radiator or elsewhere. Might have to give that a shot as it should cost me nothing. I've half assedly tried to inspect the water pump for leaks at the weep hole, so I may try jacking to car up to take a better look tomorrow.

Having bought new oil and a filter along with the thermostat housing, and adding in the battery, I'm just shy of $500 into my "DIY" repair. Pretty soon here I'm going to have to cut my losses and accept defeat by taking it to the dealer. Still holding out hope that one of you mini-wizards will instill some magical knowledge on me and I'll be able to sort this out myself though...

Any advice at this point would be greatly appreciated!

 

I believe that thermostat fault is a permanant fault, meaning it will continue to kick the fan on, show the symptoms as if the fault were currently present until you clear it out. Although the DME may not be put into limp mode, it will default to certain behaviors to avoid any potential engine damage.

I believe most aftermarket scan tools should be able to clear it out (maybe an auto parts store that does it for free?), although I admitedly haven't used anything other than ISTA and snap-on solus.

It may also have logged some engine temp signal communication faults for any other modules that usually recieve that signal from the DME, so doing a complete fault clearing of all modules wouldn't hurt.
Good luck homie.

 

Thanks for the insight! I guess I just assumed that having my battery disconnected for 30 minutes or so while buying a new one would clear any codes, but I suppose there must be some capacitors in there that retain fault info. I'll limp it on over to Advanced Auto and see if they can clear the code for me. I'll follow up with my findings after work. Appreciate the help thus far guys!

 

Success! Auto parts store employee came out and cleared the code free of charge. Car runs great once again! I honestly feel like a fool for not having had that done sooner. Guess I'm in the market for a real scanner now...

Thank you all for your help! Really do appreciate it!