I have Cooper S 2009 (R56). I noticed that the coolant reservoir is empty. Even after I refilled it it got empty after a few days. I took it to the dealer and they told me that I need to replace the thermostat (the diagnosis was for free). I didn't have any engine check. The interesting thing is that after I returned from the dealer the reservoir didn't empty for at least a week. After a week the level of the liquid decreased to min mark and stays there. It's been already 3 weeks and the level didn't change. Can you suggest what could be the problem? If I have the leak why the water stopped decreasing?

 

The radiator was likely almost empty when you noticed the tank was empty the FIRST TIME...
SO IT TOOK A COUPLE FILLINGS to "catch up" and fill the full system...
Bet you will still see a slow loss till you fix it..slowly getting worse...

 

These thermostat housings fail every 40k-75k depending on your climate. Made from plastic is the reason why they fail.

 

Amen to that.

They're also known to fail if anyone does any work around them, changes hoses etc. They're just brittle pieces of junk. I also had to replace the pipe that went from the Thermostat to the waterpump as it had cracked at the join (perhaps I'm too ham fisted).

 

I have the worst case scenario because of where I live, I'm 15 miles from the ocean and the temperature differences can be 15 to 20 degrees difference. It could be 90F at home and 70F at the beach and this causes parts to expand and contract in a very short time. Not good for brittle plastics.

 

My son recently had the coolant reservoir and pump repaired and it wasn't cheap. It started when we notice coolant leaking from the front quarter panel.

 

Even at 50k miles one who still has the plastic water pump should seriously consider replacing it with Mini's new metal pump version. Wish Mini had come out with a metal thermostat housing.

 

Did you replace the thermostat ?

The reservoir can leak, but since it stopped might be because the thermostat was replaced and then after refilling the reservoir it finally bled most of the air out ?

If thermostat was not fixed its would not leak, then fix itself ?


Some great DIY here on the thermostat , waterpump , and expansion tank:

Are waterpump have the the newest metal housing.



DIY thermostat:

https://www.northamericanmotoring.co...hermostat.html

https://www.northamericanmotoring.co...8-no-heat.html

 

I had two waterpumps fail prior to 30k miles.

 

Both plastic ?

 

If you all need a hose for the overflow tank. You can use the c87679 from autozone. It looks the same way as OEM and fit just as good.

 

Brand and metal or plastic version?

 

Guessing they were both plastic ?? Before the change over to metal.

 

I honestly don't know. Both were covered under warranty. I bought it new in October 2012

 

the bmw designers have NEVER had the consumer in mind when it comes to product deign. they have always had coolant issues when it comes to coolant, electric windows and their so-called technology package. i have had three bmw's and three mini's so far and have been accustomed to the frailties of this marque..not that I agree with concept..I just replace these items as the recommendations from forums and bmw arise.
my R53 and now R56JCW have been reliable except for the iPhone interface in the armrest. The dealer NEVER got it to work on my R56 and if you ask a parts guy at bmw, you will discover they have the same problem.
Bottom line: stay on top of the cooling system as it could result in major problems.

 

@ECSTuning, it's been a month already and the level of the coolant is STILL on MIN mark (it didn't change). I stopped the car after driving an hour (the engine is still on) and I noticed that the coolant doesn't boil. Shouldn't it boil at least a little bit when the engine works? I recorded the coolant and This is the link to a video. Is it fine? I also noticed that sometimes, rarely, I hear a fan fan starts to work vary noise and then stops.

 

You need to fill it to the middle point where the two halves meet, it's not supposed to boil and if it was you would have another problem. Boiling is an indication that you're losing air pressure out of the cooling system.

 

@Systemlord, I fill to the middle point, but it reduces to the MIN point and stays there. I understood that the leaking speed can very depend on the temperature, but it's strange that it goes down to the MIN point and stays there. So, you're saying the coolant should stay still as in the video?
The second question is what about the fan? It's never happened before.

 

Did you replace the thermostat housing yet?

Coolant should NEVER boil. Your video shows your coolant below the half mark, dealers always top off your coolant where the two halves of plastic housing come together. Another possibility is you might have air trapped in your cooling system.

 

I haven't replaced the thermostat housing yet. I'm trying to understand the whole thing. I thought that if it's leaking it would leak all the time. Even with a very very slow speed the coolant should go under MIN mark at some point. But, it stays there.

 

Here's what happens to all thermostats that fail, the thermostat housing leaks at the base on the bottom (plastic gets brittle & cracks), it then drips on top of the transmission case and if the leak progressively gets worse you'll see the coolant drip down the rear of the trans housing and onto the ground. If your coolant is leaking slow enough to dry up on the hot tranny case you'll not see it. I don't trust dealerships either, you gotta take what they say with a grain of salt.

 

+1 cracks or leaks at the bottom slowly onto the transmission. It should not boil and should be at the half way mark. Check that thermostat first.

 

@ECSTuning, 1 - what by "half way mark" you mean? As I said, the coolant goes down to MIN mark and stays there (it's been already more than a month).
2 - By "check the thermostat" you mean I need to dig in and pull out the thermostat housing, right?

 

1. Should be above or at MIN mark and steady. Reach under the expansion tank or look on the next oil change for cracks at the bottom.
2. No , a visual inspection above the transmission and of the thermostat housing locations to inspect for a small leak, also as a double check to insure you don't have a leak. That's the most common location for a leak.

I just want to make sure there is nothing missed.


Trying to figure out if a small leak then stopped or if it was just the system burping out the air over time.


Also did you have the thermostat replaced by MINI , that time ?

 

Actually the last oil change was a few weeks ago.
When I came to them in Schaumburg, IL and asked about the coolant, they put the car on the lift and checked. They told me that the leak is from the thermostat housing since they saw evidence on the top of transmission (green or blue spots, I don't remember the color) They even showed me. I tend to believe them since they know me very well (it's a long story why). Anyway, the MINI didn't replaced the thermostat.
Recently, I started to hear, relatively many times during the driving, the fan turns on. Also, sometimes, the fan stays on when I turn off the engine. Can this be related? (Should I start a new thread for this?)