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Coolant Issues that no thread has helped so far with!

7K views 23 replies 10 participants last post by  Noseypoke 
#1 ·
Hey all,

I have done quite a bit of research and here are just the facts:

I have a 2007 Mini Cooper S
few weeks ago I had a coolant leak in the housing, the car steamed up and I towed it home. So I bought a new thermostat housing and installed it no problem/no leaks

the problem:
after about 10 km of driving a code on my reader tells me that P0128 Thermostat below regulating temperature.
after a bit longer driving I get the code P0112B which I believe is a implausible temperature BMW/Mini specific

I thought it was the coolant sensor so I changed the new sensor with the old on, no change
I bled the system and still no change
I have looked on the cars computer while driving around and the cars temp is about 40C (at cold start) and after about 15kms of driving it is around 70C at the most.

My thoughts:
I believe it for sure it isn't the sensor
I don't think it is the thermostat stuck open/closed as the thermostat is brand new and I can see the temperature go down when I am driving (just small fluctuations)
I know the coolant level is good, and the mixture is right

If anybody can help me I will be eternally indebted to you!
 
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#7 ·
I don't think it is genuine, but the housing was the same in every way and stopped the leak that the car had in the housing, and mine is the heart valve so there is no way i put it in backwards I don't think you can actually even do that if you wanted to.

the thermostat itself came already set into the housing, but I am confident that it is correct, the company I ordered from is offering to send another...
 
#9 ·
Sounds like the thermostat to me. Could be the block had debris/built up in the recess, or the seal might have been pinched slightly and as previously said, it could be a faulty stat. They do cycle rapidly by opening and closing and this help them keep the constant 93 degs, 70 degs is too low and will cause you to burn excess fuel, as the ecu will think the engine is still cold and set mixture accordingly.
 
#10 ·
Well guys the company said they would send another so whats another couple of dollars in shipping and an hour of my time?

I'll get the new stat and give'er another go... I'll tell you all how this goes soon!

I will give the coolant fan and mass airflow a look at in the mean time, thanks for all the advice!!!
 
#11 ·
The two stage cooling fan are a well known problem on the Gen 1 Mini and the resistor seems to fail quite commonly. I'm sure there are threads on here and maybe a video on YouTube on how to check it or repair it. I seem to recall it is an unsoldering/resoldering job otherwise you have to replace a bigger and more expensive part?
 
#13 ·
So here is the news, I threw in the towel took it to the dealer because they have more tools than I do when it comes to scanning things, and I stopped getting a coolent temp reading of any kind so instead of screwing things up I took it to a pro.

They told me it's a faulty thermostat... I did get it aftermarket so I am not going to make the same mistake twice, tomorrow I am picking up a thermostat from the dealer and fixing it once more myself... if that doesn't work I am handing the dealer my wallet and saying fix it lol

more news to come....
 
#14 ·
Well about time!

I went to the dealer and they diagnosed the car for me, told me it was a faulty thermostat or sensor, and since you can't change them without changing the whole housing I bought a housing from them for $210.00.

I installed the new housing today and turned on the car, first thing I noticed was that the injectors became quiet and the cooling fan didn't turn on upon start up. When I went to the dashboard computer I was able to get a temp. reading and it was at 24 degrees Celsius which is correct to the outside temperature today.

I ran the car for about 15-20 mins and the temp. got up to about 112 degrees Celsius, which is high I know, but I didn't have all the coolant back in the system, I was probably working with about 2/3 of coolant in the car and 1/3 of that was in the reservoir tank, I am waiting now for the car to cool down so I may add the rest of the coolant.

No warning lights have turned on and P112b and P0128 are currently not showing up, I have not driven the car on the road yet so if anything different changes I'll let you guys know.

Thanks everybody for the input most of you guys were right with thermostat/sensor being bad, that is going back to Amazon.
 
#16 ·
Lol jumped the gun and didn't want to wait for the tank to drain into the rest of the system... Short sightedness really. Anyway's put the rest of the coolant in and then probably half a litre which was about what came out of the housing/ rest of the system when I took the car apart.

Drove around this evening and the car sat around 107-108 with night air. I am going to do further testing when it is hot outside but so far I am satisfied.
 
#19 ·
Great news, I know how pleasing it is to cure a difficult problem. You tackled the problem with sense and determination now you can relax. Next day off travel to somewhere far away you don't need to visit, just do it because you can again.
 
#18 ·
Bit concerned with you running the engine for 20 mins without all the coolant in! How come you couldn't get ALL the coolant in as you refilled and bled all the air out of the system? Also, have you know got all the air out? Is the heater/aircon working correctly, is the electric cooling fan operating correctly?
 
#21 ·
Persevere!Take it back to BMW with this info.

I have a 2008 clubman purchased new, it covers approx. 15k per year.For the last three years I have been plagued with coolant loss and have taken it back to Ocean for investigation.....they carried out various minor tasks with no result. Eventually I managed to collar a "real" mechanic who placed the system under pressure and found hairline crack in pump housing...complete pump changed under extended warranty (£200 plus),since then no more problems.....apparently its difficult to see leakage point under normal inspection, so you need a competent person to inspect components...but I think you will find your problem will through same failure. Hope this helps.
 
#23 ·
I had a similar problem with a coolant housing leak, replace with gen part and leak cured. Errors came up straight away to tell my thermostat open circuit-a fault I had not had before. Main dealer checked and new part replaced all good.
So don't think a gen part cannot be faulty.
Just one point to add, there is a bleed point on the housing to ensure air locks are removed from the system.
 
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