04-01-2009, 12:37 AM
05 Cooper N/A

Car has been to multiple shops for overheating and a coolant leak. Every hose has been replaced, has new water pump, has new thermostat, has new cap. Passed multiple block tests and pressure tests. Holds 15 pounds [practically] all day. Has Mini approved coolant with proper mixture. No visible leaks anywhere.

Cooling system holds only around 8-10 psi while running. Will eventually (time varies from 10 minutes to an hour) build to 14-15 psi and then suddenly begin to overheat very quickly and drop pressure to around 5 psi. Place of leakage varies.

I'm suspecting cracked head/block or bad head gasket but shows none of the typical/easily diagnosed symptoms of these problems.

IATN or Identifix anyone? The shop I'm currently working at doesn't have either and neither do I.

Any help would be greatly appreciated.

04-07-2009, 04:55 PM
UPDATE: Apparently car only overheats during city driving. Pressure tested after heating car up. Quickly lost 5 psi with no visible signs of leakage or signs of coolant appearing externally.

After some research it was found that the car uses a 3 layer head gasket to individually regulate cylinder temperatures. The center layer can shift causing incorrect distribution of coolant and improper cylinder temperatures.

Customer authorized the head gasket job. I pulled the head off last night and the head is currently at the machine shop being cut and pressure tested for cracks. Cylinder 1 had twice the amount of carbon as the others cylinders, even through the intake port. This could indicate that this cylinder has been running at a different temperature than the other cylinders.

I will post again with the results after the car is put back together.

04-10-2009, 08:14 PM
Car is repaired. No more pressure woes, overheating or leaking. Head gasket took care of this little gremlin.

For any of you looking to do a head job on a mini, most head gasket kits do not come with intake or timing cover gaskets or seals. There is usually an intake gasket for the "S" models but not the naturally aspirated engines.

05-03-2009, 01:02 PM
Thanks for the post and the final solution to the overheating problem. I am looking to buy a Mini. And looking over the posts gives me an idea what to expect with these cars.
In your opinion, does this car make a good commuter car? I drive 120 miles a day commuting to work.
Also, this post gave me insight to the problem I am having with my own car, different make.

05-05-2009, 07:15 PM
Great commuter car in my opinion. Comfortable, fun to drive, decent mileage. You can even tune the "S" models to be fairly quick. A coworker of mine lives 3 hours away from the shop has an "S" with a few mods and drives it everyday. He loves it. His mods were simple and didn't noticably affect his mileage, but it is much quicker than stock.

Glad my post was helpful to you. I wouldn't be too worried about head gaskets being problematic on these cars just yet. I work on a lot of minis and have only had to do 2 head jobs. They are also a quick job, which translates to cheap (compared to a head job on most cars).

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