Hi all,
I get this really bad coolant leak when I store my MCS during the cold winters in Michigan. Especially when the temps go down to the single digits as it recently been here. From what I read here that it may be 2 places that the coolant may be coming from. One is the Thermostat gasket and the other may be the O-ring at the water pump and engine block.


Do anyone have any tips to diagnose where the leak maybe coming from? I am thinking of putting paper towels under the thermostat housing to check this as this is the easier of the 2 to replace.


Thanks all,
ARLY

 

I would check your thermostat area first.. That's the easiest like you said. They can seep a bit. also the over flow tank is another spot to check. Those tend to leak at where they were seamed together. and of course the water pump another common problem. Then you have your basic things like hoses and another thing is the radiator side tanks. It can be tricky sometimes finding the leak. Ive chased a few around my MINI before. Good luck!

 

Last week I took out the overflow tank and airbox trying to see where my leak is coming from. No luck. Couldn't find anything from above or below. Tomorrow I start on a waterpump replacement and hose inspection. Seems like a lot of work to diagnose a leak but you just can't see without removing the S/C. Any ideas before I start?

 

When my thermostat gasket leaked, it was mostly the first 5-10 minutes after
starting a cold engine. As it warmed up, the leak decreased and stopped.
I'm on my third thermostat, 2nd housing, and 2nd coolant sensor now.
Mine's an R50 which is a bit easier to get to than on the S.

 

My 02MCS has only 33K on it. The O-ring was replaced once when I had 11K at the dealer under warranty. I store the car during the winters here in MI. I get this leak only during the single digit temps during storage. I usually keep and pan underneath to catch the coolant. I does not leak during the warmer months and when the engine is warmed up. This is why I think it is an O-ring or gasket that is shrinking during the cold spells. I don't see any seeping from the coolant overflow tank. This was replaced under warranty. The hoses look good as well. The engine bay is so packed, I can not see the origin of the leak. I guess I will need to some disassembly to figure where. I see dripping about the middle-front of the car. This may be the O-ring at the water pump, but it could be the thermostat housing as well.

 

How long ago age wise was it changed since you have low mileage? If it does leak , check right under the bottom of the neck/ seal. Wonder if you have the older gasket from MINI, that tends to leak over time. Then newest MINI genuine ones look a little clear / white. #4, #5 and #8 in the kit. You can see the location on the side of the engine head.



Here is the kit for the Cooper S with the gasket / thermostat which are sold together. Plus we added the neck and bolts for a clean seal.

Thermostat Replacement Kit

http://www.ecstuning.com/Search/SiteSearch/11537596787KT3/



Thanks and hope that helps.

 

Hi All, I'm having a similar issue.
I've had a minor leak for over a year and I've just kept topping the reservoir...not my daily driver.
But recently after a pretty cold spell we have had a series of 60 degree days and there was suddenly a huge puddle under the car. I put it on the ramps yesterday to change the oil and look for the leak but I can't find the leak.
There was coolant on the plastic tray when I pulled it. Poked around and looked under then thermostat area and don't see anything wet there. Seems to be more toward the front end.

 

Suggestion. It's helpful to post your mileage with your issue. My R53 w/171K was leaking when it was cool in the morning. Mine was the seal in the water pump. It leaked a small amount for nearly a year. When it got up to a pint a week I replaced the water pump. If your over 125k I would replace pump thermostat and check and change the oil in both sides of your supercharger. Then you can drive another 100k with little worry.

 

Sorry, This is on a 2004 S with only 43,500 miles or so.

 

No apology needed . With that low of mileage my guess is a thermostat. How did you get a 2004 with that low of miles???

 

I've had it for about 3 years and had low mileage when I bought it. Drove it daily for the first year then changed jobs and was furnished a vehicle for work. Only driven on the weekends and for errands for the past two years.
Planning on fixing this leak and then we need to sell it.
Here is my ad on the NAM. https://www.northamericanmotoring.co...65#post3889265
She's a sweet one!

 

With your leak more toward the front it could be the water pump or the water pump flange