Hi guys. 06 Base model with 97K miles. It began overheating while stuck in traffic in the afternoons with the A/C on. That was the only time it would overheat. The A/C would start blowing warm air and the needle would shoot up. As soon as traffic started moving it would cool down.

Both low and high speed fans are working.

It was low on coolant, couldn't find an obvious leak. I added coolant and it continued overheating. I put in a new thermostat and it continued.

Around this time I also noticed it was leaking oil from the oil filter housing, so I went ahead and replaced that gasket. Seems unrelated at this point.

The car began idling poorly and would jump hard when putting it in drive and reverse. Took the battery out, cleaned all the terminals and cleaned all ground points in the engine compartment. This seemed to fix that issue. On a side note, when I removed the ground strap on the passenger's side front (forgot to unplug the battery ground when I did this) the PS fan cut on by itself.
Found the PCV breather hose boot was dry rotted and while I was working it snapped in half. I have a new one coming. Also noticed the air filter was very dirty and I will be replacing that tomorrow.

I also went ahead and flushed the coolant system. I replaced the coolant with a 50/50 water diluted Prestone universal coolant.
The engine started overheating while driving normally and the heat would start blowing cold air.

I burped the coolant system as well as I could. The passenger's side bleed valve snapped off while I was working. Had to order a new screw today. The car seemed to be doing well until I was on my way to work. The engine began overheating while driving normally. I let off the accelerator and the temp went down. It would stay at half way for about 5 minutes and then begin going back up. Again, I would coast for a while and it would go back down and stay at halfway for a while.

I'm at my wits end. What am I missing here? I would also like to note that throwing new parts at it has still been cheaper than taking it to my local foreign car repair shop for diagnoses.

 

Keep trying to bleed it after you get that new bleeder screw.

You already did the thetmostat so there's only a couple things left if bleeding doesn't help. Radiator could be bad, or the head gasket/head could be bad. Dipstick clean? Could just be burning the water too if it's a head issue.

Best case is it was just low on coolant from the crappy reservoir leaking, and you just need to get it bled better.

Good luck, at least you can do the repairs yourself and aren't at the mercy of some shop.

 

Yup, the dipstick is clean. I'm not getting any smoke out of the exhaust. I think tomorrow I'm going to take off the valve cover just for giggles and see what its looking like in there. I'm also going to check my thermostat and make sure the weep hole is positioned correctly because I really don't remember double checking it when I was installing it.

 

Sounds like water pump is not working. Could be on the way out/ gone
Good Luck

 

The thermostat only fits into the stock housing one way, you would know if the thermostat was in wrong.

Have you tested the cooling system cap? Simple point of failure that can cause an overheating condition.

Water pumps on the Coopers aren't very common failures.

Start with pressure testing the cooling system and the cooling system cap. Is the radiator or condenser covered in road grime and debris? A poorly flowing heat exchanger can also cause problems.

 

I don't know if the recovery tank on the 2006 Base is the same as my 2005 base, but that unit is not pressurized, the lid just snaps on. I've changed the thermostat housing as well as the thermostat,several times, that things still boils over from time to time. Was experiencing the same problem in my 06/R53. It has a different expansion tank which is pressurized, which is known to leak. I changed that unit to a metal tank and that solved my problems on my R53, still boiling over from time to time on the R50.
Do you have a pressurized expansion tank on your 06/R50?

https://www.amazon.com/URO-Parts-17-...05+mini+cooper

If you have the unit below, I would start there by getting a new unit.

http://www.discountbodyparts.com/cat...?dbpcid=gglpla