Intermittent interior heat and yellow coolant temp warning light
 

2008 Cooper S with 81K miles.

A few days ago, the yellow coolant temp light illuminated for about 5 seconds while I was in traffic. It went off quickly and did not repeat. Yesterday we had a kinda cool morning, and I actually used the interior heater for the first time. Here is what resulted:

• No warm air at idle, even after car had been driven plenty to warm up.
• When under way (at revs), periods of good heat and then periods of cool air
• No rhyme or reason on when it was warm, and when it was cool, although always cool at idle.

No coolant temp light since that one time. Coolant level appears normal, maybe slightly low.

Does all of this sound like a water pump failing? I've done a few searches and I found a few indications this may be the culprit.

Normally when somebody says they have no heat the best bet is low coolant levels. With that tstat housing design of the Gen2 I just don't know.

I did check the coolant level the day I had the warning light, and it seemed normal. Now I realize I checked it when the engine was still warm, just after I got home. The level in the overflow tank seemed correct.

BUT it is, alas, low. I haven't driven the car in days, and I just checked it; my coolant tank is empty! Egads.

I haven't noticed any leaks, and my oil looks good. I just did an oil change last week, and did not notice any coolant contamination. I've had a blown head gasket on another car years ago, so I know what the oil looks like when coolant mixes in.

Looks like I figured it out. It was low coolant. So, where is my coolant going? Well, that took about 3 minutes to figure out. Using a strong LED flashlight, I began looking around the usual culprits, looking for dampness.

Water pump? Nope, looks dry as a bone, best I can see the damn thing.

Coolant tank? Looks fine, no leaks.

Thermostat housing? Aha!! Below the thermostat monstrosity, in nooks and crannies on the top of my transmission, was a fair amount of coolant. I'm assuming a thermostat-ectomy is the answer.

Wonderful. :roll:

Sometimes a blown gasket will leak directly into the cylinder and not mix with oil, getting pushed out the exhaust. Hopefully the t-stat is the leaker.

If you do the thermostat yourself, make sure that you find the bleeder and use it. The system will not bleed itself and you will have issues.

Since the coolant will be drained, it makes sense to change the waterpump also, unless it has already been done. Early 2nd gens had a plastic housing, the replacements have an aluminum housing.

Have fun,
Mike

My tip when changing the T housing, get new hose clamps or better still, screw type clamps (we call them jubilee clips) as your old clamps will most likely not reseat exactly and you will get leaks (I got two).

Keep us posted....as mbwicz mentioned, consider changing your water pump...I'd add consider changing the plastic pipe between the pump and the thermostat....they get brittle with age.

Hope it goes well.

Oh yeah - from my experience, I'd go with an OEM MINI thermostat....I had an aftermarket t-stat fail about at about 2,000 miles....PITA

Just to wrap this up, it was the thermostat housing. Although I do most of my own wrenching, this one I took to the dealership. Too much stuff going on in my life to have the time to spend tearing into the 8 zillion things that have to be moved to get to the thermostat housing.

And I have a good dealer service department so I trust them. I think the total bill for parts/labor was something like $425.

That's what I was guessing. NO heat or inconsistent heat is the first symptom that's what it did on my R56 2007. https://www.northamericanmotoring.co...8-no-heat.html

If the bleed the system good afterward your MINI should heat up on the heater side fast and blow really hot air after a couple minutes which revving the engine. Also, you should not hear a water noise or trickle noise in the heater core if it was done right. Sounds like you are good now. :)