Hi. I have a 2009 Cooper S in Arizona.
Is it normal for Mini S's to have cooling issues? BTW, Temps are nice and cool now though...low 70's.

The car had been giving me the low coolant symbol every few days. It would be a little low and I'd top it off. ...All better. Where's the water going? No leaks visible.
Then one time it was more than a quart low on oil, water too, and started smoking white smoke from the tail pipe really bad. But didn't say anything about heat. No warnings on heat. I filled up water and oil and let it cool and then seemed fine.

Since then, the car has been giving me the notices that the temp is getting high and to drive moderately and the later tells me to shut the engine off due to overheating. Even though I was driving super moderately. Why Isn't there a gauge? What the F is wrong with these people? Give me a heat gauge if nothing else on the car please!

Details: The coolant level goes down a bit and I have to frequently top it off. There are no visible leaks of any kind. The heater always blows room temp air not hot. It doesn't seem that hot actually.
My guess is that I have at a minimum, a head gasket leak. Water to exhaust port. (No water in oil.)
Does this sound right? Or,... somebody else said...water could be pooling somewhere internally because of a thermostat leak?
Is the gasket hard to do yourself? Will the head be warped? Is it aluminum? Hah. Okay that's a lot of questions. Sorry.
Anybody want to weigh in on this?

Thanks for your help!
John

 

I have no specific Mini experience but you need to check for a head gasket leak, a leak anywhere in the cooling system. My advice is to drain the cooling system -- into a clean drain pan -- then pressure the system -- do *not* over pressurize the system -- and see if it holds pressure. If it doesn't then you need to identify the leak. (As an aside with the coolant in a clean drain pan you can easily see if it has any oil in it.)

Normally I recommend a hot pressure test which involves topping up the cooling system -- distilled water can be used -- and being sure the coolant cap is properly installed and tightened down start the engine -- turn off the A/C -- and drive the car around town just normal town driving until the engine is up to temperature, the radiator fan comes on due to coolant temperature. I also use an OBD2 tool to connect to the car's OBD2 port and monitor coolant temperature. At home in the driveway or garage raise RPMs to just over 1K and hold until the radiator fan comes on. When it comes on shut off the engine. The heat load of the engine will raise the coolant's temperature and pressure and if there's a leak you'll likely find it by following the gush of hot coolant. Which reminds me, keep your distance as a hose can spray you with hot coolant.

But this is not a normal case when it is suspected a head gasket or a cracked head or something is possibly letting oil and coolant intermix.

Listening at the intake or exhaust manifold or even better removing the plugs and turning the engine by hand slowly to close each cylinder's valves thus forcing any air leaking to have to flow out the spark plug hole can help you determine if the leak is the gasket or even from a crack in the head.

Keep track of the cylinder each plug came from. If you find a plug that looks very clean that's a sign of coolant getting into the combustion chamber.

'course, you check all the hoses and connections, the radiator, etc. for any signs of a pressure leak and signs of a coolant leak. The leak doesn't have to be a bad gasket or head.

(Later after you have found/addressed the leaks be sure the cap is good. With other cars (Porsches) I have had to replace the coolant tank cap the original ones leaked under pressure and let vapor escape to the point the level could be down nearly a gallon in just a few weeks worth of driving.)

But if the head gasket or possibly even a cracked head is leaking you'll have to remove the head and deal with that. If the head is cracked it might have suffered from localized overheating and while in some cases welding may resurrect the head it can be warped and if so may be scrap. Check the head first for flatness. (My toolbox had (still has) a precision straight edge to check heads and blocks for out of flat conditions.)

Also if the gasket leaks too long it can cause some erosion of the head metal and this compromises the head gasket sealing surface possibly even the block's gasket sealing surface. In some cases the head can be resurfaced taking just enough metal off to bring the gasket surface back to snuff. Ditto the block. (Buf of course the engine must be completely disassembled and after cleaned to the nth degree. But one can't off very much metal as this can result in too much slop in the cam chain. It really takes an expert on these engines to know what's ok and what's not ok.)

Might mention that a cooling system that loses coolant can't hold pressure. What can happen then is when the coolant is hot the lack of pressure can allow the hot coolant to flash to steam at the hottest areas of the head. When this happens a steam bubble forms which can keep cooler coolant from flowing over the hot surface and this localized overheating can cause the head metal to crack or even soften.

Take a sample of oil and send out for analysis. Among other things antifreeze compounds will be checked for and if any present this is a sign coolant is in the oil.

Might as well replace the water pump and T-stat while you are there. One or both could be bad and you get the engine back together and before you know it has overheated again and you are back to square one.

If coolant was in the oil or even if it was not be sure to drain the oil and replace the filter then fill the engine with the correct type and amount of oil. Run the engine a while at least long enough to get the engine nice and hot -- assuming it doesn't manifest any untoward symptoms when running -- and nice and hot is when the radiator fan comes on. Oh, you do this with the A/C off as turning it on can have the radiator fan running all the time. After you shut off the engine drain the oil again and replace the filter again and refill with fresh oil.

If there has been oil in the cooling system you might look into a flushing compound you can use -- probably mixing it with water -- to remove any traces of oil from the cooling system. Afterwards drain this and refill the cooling system with a mix of the proper antifreeze and distilled water. The flushing compound may have other instructions so you go by those. I've never had to flush a cooling system due to oil contamination.

The above is *not* a complete coverage of this but gives you I hope some idea of what's involved. First is to confirm there is a leak and from where. Knowing this then helps you to know what the subsequent steps are likely to be.

 

To put it succinctly... yes these cars have common cooling system failures. Both the thermostat and water pump are common failure points. One of them is probably leaking. It's unlikely that you have head gasket issues. As you've found the car will shut down to save itself from overheating to the point of warping a cylinder head. The heat blowing lukewarm is probably because there is a big bubble in the heater core because you're losing coolant. There are DIY videos/posts on both the water pump and thermostat. They're on opposite sides of the engine and not super difficult to DIY depending on your experience. First thing is to figure out where the coolant is going. I'd bet the thermostat is leaking and coolant is pooling on top of your transmission. Get in there with a blacklight and usually you can see the coolant trail.

 

Sounds like some more diagnosis is needed, but likely need to pull the head. We don't see head gaskets fail very often it's usually a cracked or warped head so I would go in the direction of making sure it is good.