Hi Guys, So my '05 Mini Cooper (R50) has a history of overheating since I got it back in 2014. The first time I figured out it was a bad radiator maybe 6-7 months into having the mini. So I replaced it, bled the coolant system, checked for any other leaks tested the car for about an hour and was on my way. Then, 3-4 months later, the car overheats on the freeway again. Turns out the radiator I bought was faulty so I dug up my warranty and exchanged it for a new one. About 2 months later, the car overheats AGAIN! What was it now? The thermostat. So i replace that as well. Again, check for leaks, bleed the system, test the car and be on my way. Keep in mind, all these times, the Overflow tank I would fill it and at times it would maintain and sometimes it would be dry to the bone. Now it has been almost a year since the last overheating incident and the car overheated while idle on a parking lot where I stopped by for food after a drive home. So i checked the heater and it was blowing warm air on HIGH. So I opened up the bleeding screws and I heard air hissing like i anticipated. So i refilled the Overflow tank and within 2 days it is now empty again. I am going to pressure test the system but anyone have any idea where the leak might be? I checked for a leak this morning but i cant seem to find one. And I can smell the coolant when I open the hood but am not sure if it is from the bleeding I did of the system. I just feel so defeated. I can't win with this car and I've had other issues like a bad clutch, alternator and broken air filter box that I've fixed so I don't want to give up. No, my oil is not milky and am not blowing out white smoke so I dont think it is a blown head gasket.

 

Rent a pressure tester from vatozone or advance auto first. Do you see any puddles at all? Any evidence of a leak in the engine bay? If not, I'm guessing it's burning up at a real slow rate so you just don't notice it. Give the exhaust a sniff to see if it smells sweet.

 

Did you change the housing with the thermostat?

 

I'm betting it's still the head gasket. It might have a hairline crack or cracks. Hence while you keep getting over heat slowly in time. With big crack you'll notice the smoke more.

 

No puddles at all and the exhaust smells fine. I havent seen anything around the engine bay that appears to be leaking. The wierd part is that before with other leaks, I always had to top off the coolant because it was low. But this time around (i havent added any since i changed the thermostat) it is always filled up. So there cant be a leak from the areas im familiar with. I just cant explain it. Its never been like this. I'm definitely going to pressute test it this week. Friday the latest.

 

I just don't think its the head gasket. I'd see some contamination between the oil and the coolant right? And the oil is as clear and slick as I always keep it.

 

I didn't but I inspected it when i changed the gasket and it looked very good for its age. Didn't think it needed changing.

 

I had a similar problem on my 06 R50 and like daviday...I'd recommend you replace your thermostat housing, gasket and while you're at it replace the thermostat if you cannot figure out what's causing the problem. For a few dollars more you could also replace the coolant sensor that sits just to the right of the thermostat housing if I remember right. I believe the thermostat housing comes with a new cap so that should button up everything nicely.

Before I did any of that I'd recommend getting a dye kit and see if you can find any leaks around the thermostat housing. You might be able to buy only the dye at an auto parts store and borrow the other stuff (glasses and light).

I thought I was going to have to replace my radiator but after two times of replacing the thermostat & gasket I finally got it right...the first repair lasted about a year and it started overheating again...the second time I replaced only the gasket & the sensor since the housing was only a year old. I double checked the torque on each bolt too! Have not had any issues now in a few years.