So here's my problem. I have searched and looked at all the overheating threads but haven't found what my issue is. I have an 05 mcs with an overheating problem. It started when I noticed the coolant tank was empty and needed toping up. I don't think it's a leak because somedays it's full and others it's empty. There is minimal fluid under the car and it will still be empty. Lately when it gets super hot and the fan kicks on the cars temp further increases. I get out of the car and slowly take off the expansion cap. As I do this I notice initially there's no coolant in the tank. Just air. But as I let out the air slowly taking off the cap the tank begins to fill and then once the cap is removed all the coolant that made it's way back into the tank leaves the tank through the bottom tube. Requiring the tank to be topped of again. I have replaced the tank and cap and this weekend I'm going to change the thermostat. Does anyone have any ideas what this may be. Im out of warantee and would prefere to fix it myself then take it to mini. Any help would be great feel free to respond here or pm ne. Thanks in advance.

 

It could be air in the system. I would try doing a bleed first and seeing if that fixes the problem.

 

I'm having the exact same problem on my 2002 S, i have asked around and people think it may be a manifold lead. I have noticed a major loss in power since this started to happen. I have no dripping, leaks or puddles around my car either. Any suggestions?

 

i have no powerloss just gets hot and then begins to boil the coolant/ water.

 

well i just dropped it off at my Mini mechanic and he thinks just from hearing what i described that it may be the thermostat housing that has a leak. He is going to check it out and let me know. I'll keep you updated. In addition to this i went out to my car today and the damn thing woudnt start, tries to turn over but wont kick. I think its the fuel pump but not sure yet :( He is taking care of that as well. Damn problems always come up when you dont need them.

 

def do. i am changing my thermostat tomorrow and possibly the housing, i will keep you informed. Good luck.

 

So, there is fluid under the vehicle, does it have color?

Fluid level in the expansion tank when cold is what you should be concerned with. When cold, the level should be lower than the tank seam, but not exposing the baffles at the bottom of the reservoir.

If there is a thermostat housing leak you will see coolant (or residue) on top of the gearbox under the housing.

If no leaks can be located, check coolant level when cold, add if needed to bring the level up to below the seam, or siphon off if higher than the seam. Operate the vehicle until hot, let the car cool for a couple hours, open the bleeder screw forward of the intake manifold until fluid escapes without bubbles then close, add distilled water to the reservoir/expansion tank if needed to bring up to below the seam. Operate the vehicle to test for reoccurring symptoms, if they return, let the vehicle cool for a couple hours, repeat the first bleed sequence plus loosen the bleeder screw just below and forward of the thermostat housing and let fluid escape for a few seconds, close and adjust expansion tank levels if needed.

 

I don't see where anyone mentioned pressure testing the cooling system after bleeding it. Check for leaks first while the system is under pressure with a pressure tester.

 

So heres the update, I replace the thermostat and housing just to make sure the housing wasnt leaking also. The total cost for the parts was $100 and change. It took me 3 hours to do without the bentley manual. The system was bleed and everything is great.

 

I have similar problem before.
Here is the pic that showed the broken gasket on my 2005.

 

Thats where mine broke. The new gasket that I got from mini was a different material. The guy at the service center said it would last longer because it was re ldesigned. The install was not too difficult.

 

I am going to drop mine off tomorrow for its free "looksie" and hopefully this gasket is the only thing that the car needs. I'm trying to save my money for MITM next month but this could set it back a bit :(