I have an 03 S model. She seems to get too much pressure in the cooling system. I went through 3 of the oem coolant expansion tanks in a matter of 2 months. So I just got a metal one online. All worked well for a day or two... until the cap broke. It's overheating because of the Cooling system pressure build up. There's no leaks anywhere else. Many people are telling me its my Thermostat. But I wanna be 100% sure, since I'm low on cash and don't want to waste money on wrong parts. Thanks! Also, don't have a temp gauge, only way I know she is overheating is cause she pukes onto the headers.

 

how did you bleed the system?

 

How much is puking onto the headers? any chance it's just overfilled? Does your car not have a temp gauge at all? or it just isn't showing that it's hot?

 

A leaking headgasket can cause excessive pressure in a cooling system....
Any other symptoms?

 

Yea, that's allot of pressure. I would do a leak down test and see exhaust or head gasket is shot.

 

You can purchase a block tester for under $40. Pour the fluid in the tube push it into your expansion tank and hold it in place for about 2 mins, if it changes color to green, your head is leaking....

 

So there is so much pressure it's cracking a new coolant reservoir?

A bad cap that's not letting the pressure out could be a possibility.

If you are over filling it it's has to come out somewhere. You only fill it about halfway.

Thermostat is not expensive and it would be the first thing I would change. It might not be the problem but for $30 it's worth trying. They do go bad occasionally.

Like pho said, make sure you bleed it correctly. It's not always easy to do, so make sure you get all the air out.

Good luck owning a Mini when money is tight....

 

Week 2 for my New to Me 06/R53. Sitting at a light today and noticed steam coming from under the hood, of course I know what that could mean. Get to the office and lift the hood, bubbles coming from the expansion tank, hopefully that's all it is. I did do a block test before I purchased it. The car has 110K, One owner with complete history. Thermostat was changed 3 or 4 times during radiator flushes. Thermostat housing was also changed. My question, should I get another plastic expansion tank or go with a metal unit?

 

Gumbe if yours is overheating while stopped in traffic, I would make sure the cooling fan is working.

My fan wasn't working for a quite a while, and it would only overheat if I sat in traffic.

 

My fan is working, car not overheating yet. Just hoping it is the expansion tank and not pressure from the system causing the tank to go bad.

Any insight on the aluminum expansion tanks?

 

Some reuse the mini plastic cap...
Some use a regular cap...but a higher psi MUST be used, since the psi of the MINI cap is non std...
I ran plastic tanks for 10 years, and 100,000 miles....if you only fill them to the seam...just over the baffles, they last fine... overfilling them makes them vent out the top, and ultimately fail.
I got 30,000 miles on the original milky clear one....the got the free warrenty replacement to the yellow ish one that is glued better, but harder to check the level....was still on it 7 years later when it was sold...

 

Mine is leaking at the seam. I am familiar with bleeding and where to fill the tank, I'm on my 2nd Mini.
My question is: Does anyone have any insight with the aluminum expansion tanks?
Thanks in advanced..