Coolant boiling over on Mini Cooper 2006

[Boothy01]

Hi hope some one can help the wife has a
Mini Cooper 56 plate and 2 days ago she said
The temp gage went to red so I topped up
And now it is just boiling over when we drive it I
Left over night and can't see any leaks and
When started and left from cold seems fine
Till we go anywhere it has to be loosing water
As put a lot in hope u can help
Thanks

[The Nun]

Thermostat might be stuck in the closed position, although they normally fail open but its not unheard of to stay closed?
If it overheated severely in can do the head gasket in too, also topping a overheated engine up with cold water without waiting for it to cool down does the head no good either.

[Boothy01]

Quote: Originally Posted by The Nun (original)

Thermostat might be stuck in the closed position, although they normally fail open but its not unheard of to stay closed?
If it overheated severely in can do the head gasket in too, also topping a overheated engine up with cold water without waiting for it to cool down does the head no good either.

Hi thanks for reply if head gasket had gone
Would the oil not be like Milky Way as oil seems
Fine I had a new thermostat fitted about 8 month
Ago could be that I surpose could there be a
Air block as wife never checked water till temp went
Up how can I check if gasket has gone
Thanks

[mab01uk]

As you say the themostat has been replaced and the coolant level has been allowed to drop low, I would check and bleed any air from the system that may have entered as a first measure as this can cause boiling over you describe.

[marque]

Hi ya

Sorry to here your having problems it could be a few things.
Firstly you need to fill and bleed the cooling system this can be a pain, but has to be done correctly take your time.

You need to use the correct coolant and not just water as water bolls at 100 deg c. the minis run around 90 to 120 deg c.
it needs to be the correct coolant Halfords sell it

Halfords | Comma XStream G48 Antifreeze Concentrate 5 Litres

This is what I use in my minis and its approved for bmw just follow the mix ratio

Once this is done you need to see how fast the coolant temp comes up to operating temp.
You should be able to tell if the thermostat is opening but feeling the coolant pipes from the Rad.
If car starts getting hot quickly and the rad hoses are cold it's a good chance the thermostat is shot like the num says but could also be the water pump.

The over heating may also be because the radiator low speed and second stage fans are not cutting in to cool the coolant, so you need to check this as well when you are warming the car up.
If you know someone with a scan tool or similar you can keep an eye on the water temp and make shore the fans cut in at the correct temp, and also you can see a slight drop in temp as the thermostat opens
If the fans don't check your fuses and relays for the fans and then temp sender

If you are worried about the head gasket a hydrocarbon sniff test can be done on the coolant this will tell you if the head gasket is leaking in to the cooling system.

Hope this helps

[hibbs]

Easy way to check stage one fan is to lift the bonnet. Switch on the aircon and the fan should start.

If it doesn't, then that's the reason it is overheating (and its probably the resistor in the fan assembly).

Finally, don't read too much into the temperature gauge. It only shows overheating in extreme circumstances as it is controlled by the computer and programmed to register "normal" unless there is a big issue.

[Denise]

Hi I am new to this forum and only had my mini for 2 months but my expansion tank was always blowing out its water did all the checks as above but didn't cure it I took it to a garage they pressure tested the radiator and it had a leak, replaced that and it cured the problem hope this suggestion helps

[Boothy01]

Quote: Originally Posted by Denise (original)

Hi I am new to this forum and only had my mini for 2 months but my expansion tank was always blowing out its water did all the checks as above but didn't cure it I took it to a garage they pressure tested the radiator and it had a leak, replaced that and it cured the problem hope this suggestion helps

hi thanks for your replies i will let you know the out come
its just strange as went in it last night and heaters got hot quick ond coolent
boiling over but rad was stone cold but fan was kicking in yet topped coolent up left over night and checked this morning and no loss of coolent or leaks
so only when car is going that i seem to be loosing coolent and oil is fine so it cant be head gasket can it
thanks all

[flagpoint]

Hi all,

I'm also new to this, my son has just bought an 02 plate mini. I have read loads on this subject, but i have an added issue !

Like everybody, my heater blows cool or mildly warm, the temp gauge sits happily at the half way mark. It does not lose any water, and i have checked the heater cable and it operates fine.

If I turn the blowers off for a while and then turn them on, there is slightly more heat, but not for long. What I find strange is that, the water level in the header tank raises, then the fan kicks in and it lowers again ? It gets slightly higher than Max, but never lower than min ? I have bled the system at the two bleed screws and only get water, no air.

I am looking for ideas ? what do you reckon Thermostat, Heater matrix ? Car runs fine and seems to run as normal, its just frustrating and with cold weather approaching, not good !! Thanks in advance.

[mab01uk]

Based on a couple of similar heater problems here on Mini2 in the past, it could well be the heater matrix is partially blocked after 10 years of use:
Lukewarm Heater Matrix problem:
http://www.mini2.com/forum/first-gen...rm-heater.html

The header tank is also known as an 'expansion' tank as coolant expands when hot, so the level will tend to move between min and max depending on coolant temperature.
"There are two correct level marks on the reservoir because the coolant in the system expands and contracts in volume depending on how hot it is. The coolant level should be at the lower mark when the vehicle is cold. The coolant level should be at the upper mark when the coolant is hot."
http://www.cdxetextbook.com/engines/...m/adjcool.html