Last June I headed down to Souderton, PA to let the talented Mike Marzo perform his magic on my 05 S with 145K. He replaced the flywheel, clutch, Oil filter housing gaskets, valve cover gasket, oil pan gasket, A-arm bushings, front sway bar and bushings, new thermostat and thermostat housing, new water pump and service the supercharger (btw, the oil looked virginal and no loss of oil plus the unit looked perfect). Got all the parts from Aaron @ Outmotoring and he was the person, btw, who recommended the indomitable Mr. Marzo to perform all this needed maintenance vs. Detroit Tuned or Helix 13 in Phily that I considered utilizing.
Fast forward to yesterday and was heading home from grocery shopping when I saw vapor smoke coming from the hood and saw the the temp gauge was pegged and the red light was on. Immediately shut the MINI down and got a tow home. Made plans to rent a U-Haul to tow the old girl down to Mike's 3 bay garage and tried to keep my spirits up. All I could think was defective thermostat or water pump, broken super changer teeth not engaging the water pump or blown head gasket. After conferring with Mike he was so gracious and accommodated me right away which help with my depressed attitude since I was 72 hours away from a planned 6 hour drive to Frederick, MD to start my first vacation since July of 2019. After discussing the issue with the uber professional Aaron @ Outmotoring he recommended replacing the coolant over flow tank and cap since they are notorious for failing since he said he has never seen a new thermostat or water pump fail so quickly, yet he said the coolant tank caps are known to fail quite a bit. Please keep in mind I replaced the tank 21 months ago with a new cap so I'm thinking I got a hell of a drive to PA and its gonna cost me $350. just to rent the truck and dolly. Grasping at straws I went and bought a new tank and cap today and presto changeo, no more over heating and the MINI is back up and running.
So, wanted to give kudos to Mike Marzo of MINI Rescue and Aaron @ Outmotoring for their outstanding service/professionalism and let others know that check your coolant tanks and caps. Nothing worse than being broken down on the side of the road on a hot summer day.

Better yet, keep a spare tank and cap in your MINI at all times with the tools to replace them.

OK, time for me to pack for vacation time!!!!!!!!!

 

Although I'm still using the OEM plastic tank and cap. They do fail. I keep a new spare one in the hatch.
I haven't upgraded to an aluminum. However, having a $35 spare on hand is cheaper than a tow truck...or warped head.

Glad to hear everything worked out for you. Some very good people had your back

 

I had expansion tank cap fail after 4 months in use! I installed it September last year and in January this year, I began seeing coolant on top of the expansion tank when I did my underhood checks during gas fill ups and that tank of gas, I had an overheat - not caused by the bad cap.

It wasn't until I fixed the overheat issues that I found out the cap was bad.

I think I will start carrying an extra cap in my boot.

 

OK, wanted to update this post for a long time. Turns out it WAS a defective thermostat and not an issue with the plastic overflow tank. My mechanic replaced the defective one and I thought that was that. Got home and started to get a code indicating that the engine temp was too low. After suspecting another bad thermostat I drove back down to my mechanic and he installed a new one. Looking back we decided when we were checking the replacement for the defective new one that the heat gun used to check *ucked up the second replacement, (See movie)
So, it took 3 attempts to replace an original thermostat, albeit it was 17 years old, that was working fine and cost me over $480.00 in towing(upstate NY to Souderton, PA), $75.00 in gas and tolls and $350.00 fee to installing for a replacement defective thermostat. He did the 3 rd one at no charge. That's close to $1000.00 to replace a $14.00 part. My *ss is still stinging from that one!!

 

Loose end link. It’s always a loose end link