So I had my thermostat and coolant tube replaced recently. Picked it up from the shop, drove it a day or two and no issues. Drove it the 3rd day about 50 miles around the city with a/c and sport mode, and Amber to red temp light came on. Pulled over and coolant was coming out of the reservoir. Towed back to the shop and they couldn't replicate the problem. Said he didn't think it was head gasket, could have been air in the coolant system.

Picked it up drove it home a week later since I was on vacation, and been driving it for a few days. Opened hood yesterday morning and found coolant slightly below mid. Pulled the cap off and topped it off. Drove it around no issues. This morning see the coolant tank a good amount above max. Removed coolant to bring it under max. Driving it and seeing temps pop to about 110-111C. Pull over and shut engine down and see coolant tank is cometely full. Shut car off and I'm waiting for a friend to help me get it home.

Now when I added more coolant, I didn't bleed at the screw, which may be an issue. The shop doesn't believe I have a blown head gasket, and I don't have any coolant in my oil, no gas smell in my coolant, no white smoke from the tailpipe. I just don't see the symptoms.

So either I have a bunch of air in my system, or the replacement thermostat is bad and it's only opening here and there. Once the system cools, I'm going to bleed it at the screw on thermostat housing.

Any ideas?

 

Normal temp in 2nd gen mini's is about 220 deg F. Even tho it's summer, run the heater for awhile to get air out of those hoses. Also push the "MAX A/C" button and run it like that for awhile too. This will push coolant thru the hose under the radiator, which is not part of the normal coolant flow. This hose is often the first thing disconnected for draining.

If the pump wasn't changed, there shouldn't be any problem with the friction drive wheel or belt, but maybe check them anyhow?

 

So the pump and pulley were changed about 7 months ago, and I didn't have issues. It didn't start until the thermostat and water pipe were changed, which leads me to believe its just air in the system. At least I'm hoping it's that.

I'll bleed from the screw and then run the heater and see how it goes from there. Thx.

 

Let's examine these theories. You are correct about the normal operating temp but, ...

What happens when you change the position of the temperature selector **** and turn the fan to full power? The MINI doesn't have a water control valve that restricts or stops flow to the heater core. Your heater core always has water flowing through it. The function of the temperature control **** is to send a signal to the the blend air door servo motor which in turn moves the blend air door in the plenum chamber. Moving the fan switch to high only does one thing, and that's to change the speed of the fan which forces air over the heater core or evaporator coil depending on the position of the various doors in the plenum.

Now let's look at the Max AC switch. What does it do. I'll tell you, it has nothing to do with the cooling system. The Max AC switch sends a signal (open or closed) to the outside door flap. When open, outside air is allowed in the cabin, when closed, air is recirculated inside the car, so the AC system doesn't have to continuously try to cool down hot outside air expediting a drop in cabin air temperature. Like the heater core, there is no electrically controlled valve in the cooling system that is connected and or controlled by the Max AC switch. Flow paths through the cooling system are controlled by the t-stat, pressure and flow are produced by the water pump.

Reference: Bentley Service Manual. If you have technical data to the contrary, please post it. I'd love to see it.

 

So partly it seems like my radiator cap was bad. I heard hissing one day and bought a new one. It did help, but I have had to bleed the system still. (Fine, maybe there is some air still in since getting it back from the shop.) Unfortunately, I have this feeling like there's a possibility of something else. So I went and bought a combustion leak detector kit and ran it today. Drew vacuum from brake booster vacuum pump.



Fresh chem out of the bottle before the test. The bottle says let the test run for two minutes, and here's the result:



Well it isn't yellow, but it looks slightly blueish-green. So. Not sure if I should be concerned or not. Any other ideas, or am I worrying over nothing?

 

Your symptoms sound a bit like mine as described by the previous owner (intermittent overheating). I just bought my 3rd mini and it's a 2007 MCS. When I started the engine and ran it all seemed well...no white smoke out the tail pipe...they had just changed the turbo and the intercooler as well as the auxiliary water pump. Anyway...when I got the car home (trailered it) I drained the coolant to find there was a little oil in the coolant. I decided to do some other repairs as preventative maintenance (PM) since the car has 78K on it. Removed the oil filter housing and heat exchange...looks like it's possible the oil contaminated the coolant from here but am not certain. Have a new thermostat and coolant tube to replace as well. Thought I might have a blown head gasket but now I'm not sure. I'm going to put everything back together after I change the timing chain as PM and then put it back together. Will do a compression test before I button it up and see how things look. There was absolutely no coolant/water in the oil...just the other way around.