Do Mini Coopers Leak?

It’s my understanding that nearly all mini’s leave their mark.  Do most just drip oil or some anti-freeze as well?

You’ll probably get more reasons for leaks than their are Mini owners. But it all has to do with how well and carefully various gaskets and seals are installed and maintained. For example, tighter isn’t always better. Take for instance rocker cover gaskets. Putting them on is generally easy but you have to be meticulous. The metal sealing surfaces have to be absolutely clean and free of any trace of oil. Then you need to get a good, reliable bonding agent such as Permatex spray adhesive and get the gasket to sit fully even and straight. A tacky rather than slippery adhesive sometimes helps in getting the gasket to stay put. Then you lower the rocker cover carefully into place and tighten the bolts down evenly and gently. You only need enough pressure to hold the gasket in place, not compress it. Too much pressure only distorts the gasket. Similarly, it takes real care to install crankshaft and driveshaft oil seals so that they aren’t distorted or scratched when passing over splines etc.  But because they are wearing surfaces (the shaft turns, rubbing on the seal) and the sealing material ages, they eventually will leak. My car’s driveshaft seals leak a wee bit when it is left sitting unused, but not if it is driven regularly. I think someone once wrote here that they tend to dry out when not shifted regularly. On other cars, air conditioning pumps leak when not uses regularly. I suspect new cars with AC are designed to turn on the AC when you set the controls to windscreen defrost to activate the pump. It seems really counter-productive to have AC come on when it is -40 and you’re trying to get frost off the inside of the windshield.

Speaking about anti-freeze, in normal conditions, a Mini should not leak any. But you still need to check the level because most Minis do not have an expansion tank and need an air space in the top of the rad, unlike modern cars. Minis also do not generally have an overflow tank like new cars either. So if the rad gets too full, or the engine gets too hot, the coolant will expand, over-pressuring the rad cap and pushing a bit of liquid or vapor out the overflow tube, landing on the ground. So there is usually a constant slight evaporation loss due to this release of vapor. The Mini engine may overheat after you’ve turned it off because the head is hot and the coolant stops flowing. You can get localized boiling in the head which can push coolant out after you’ve parked and walked away. That’s why new cars have catch tanks, which let the coolant siphon back in as the engine cools down.

Other antifreeze losses can occur in a Mini due to loose hose connections or old, tired hoses, corroded rads and heater cores, leaky heater valve, and the worst… a failed head gasket. The last isn’t noticeable unless you experience rough running (leaking into a cylinder) or whitish creamy deposits around the oil filler cap and neck (leaking into the crankcase and mixing with the oil).

The basics of the technology in a Mini is over 50 years old. 50 years ago, these issues were commonplace in all cars, except maybe VW Beetles which don’t use coolant. Some of them had gasoline-fired heaters… rather not have that leak!

From: http://www.minimania.com/web/threadid/105785/msgthread.cfm