Enigmatic coolant depletion R52 Cooper S

[Inspirli]

I purchased a 2008 Mini Cooper S in August.

I immediately saw that the coolant was depleting, so I purchased a new tank from Febi Bilstein.

For a few months, everything was satisfactory; levels were monitored biweekly.

I was waiting for a buddy with the vehicle idling when an excessive amount of steam emanated from the hood. Upon inspection, I discovered the tank was empty and the cap had been detached.

Upon inspection, the metal valve was misaligned; I purchased a new cap that is far more robust and well-constructed.

It is hoped that the issue lies with the cap; nevertheless, there is a suspicion of a leak, despite the absence of coolant. Nonetheless, there are indications of dried coolant stains present:

[Inspirli]

I am aware that it is located near the thermostat.

I do not exhibit any apparent indications of HGF or thermostat malfunction. Temperatures are OK; heaters function as anticipated. No smoke from the exhaust; oil is crystal clean; vehicle operates smoothly.

I plan to replace the valve cover gasket during Christmas, as it appears to be deteriorating and likely has never been replaced (evidenced by some severely rusted bolts). Is there anything I can visually inspect while performing this task, given that I lack testing equipment? If I cannot identify any issues, it will necessitate a visit to the garage.

Any suggestions? This one has me perplexed.

[Radiantecon]

Purchase one of the little "sniff tester" kits.

Remove the cap and use it to extract the air from the coolant reservoir. Colour change in the fluid of the sniff tester indicates the presence of combustion gases in the coolant, suggesting potential issues such as a head gasket failure or head fractures.

If there is no colour change, the engine is mechanically sound, and the cap has likely deteriorated. That is only a cap replacement problem.

While more issues may arise, this approach will begin the process and represent the most cost-effective method to address the prevalent problems initially.

[Inspirli]

I will conduct a test.

[Cincoon]

I am not well-informed, but I discovered a location to expel air while adding coolant at the bleed screw located above the thermostat. It prevents overheating.

[MagicPod]

Examine the coolant level to see if a leak exists.

I purchased a pressure tester, however the neck of the pressure cap on the Mini is deep. Unlike a radiator cap, the pressure tester was unable to exert sufficient pressure to effectively identify any leaks.

[Radiantecon]

This testing kit includes an adapter compatible with a 2nd generation mini. Amazon Canada

I purchased one around six months ago, and it includes a lid that fits the coolant container.

I do not own a cap tester; however, I circumvented this limitation by removing the coolant reservoir from the vehicle, sealing all openings save one, and then pressurising the whole reservoir while submerged in the septic sink. Confirmed that the cap detached at the appropriate pressure and that the coolant reservoir exhibited no leaks concurrently. One must sometimes engage in unconventional thinking.

[Inspirli]

I conducted the test, which yielded a negative result for HGF; but, when opening the bonnet, I discovered that the cap was missing, likely dislodged by the pressure.

Is the pressure causing the caps to dislodge for any reason?

[Radiantecon]

The cap should remain secured. It alleviates pressure at around 21-22 psi. It should not displace the threads on the bottle.

Purchase an authentic Mini brand reservoir cover and see whether it continues to overflow. Coolant systems need appropriate pressure; otherwise, they may vaporise at temperatures lower than specified.

[LimeLing]

If the cap is loosened, it may indicate a defective thread on either the tank or the cap, as some aftermarket options do. If it fails to maintain pressure, the liquid will simply boil.

The first stage of the cooling fan often fails, and sometimes both stages may fail. This malfunction results in increased system pressure and potential coolant backup.

Certain systems may be constrained by silt accumulation, since individuals often neglect coolant replacements, leading to corrosion of the blocks and the deposition of debris at the system's lowest points.

[Inspirli]

The first occurrence occurred when I was stopped, and today it happened during very slow traffic; so, I can only infer that it occurs while idling.

It is conceivable that the fan is malfunctioning (I have tested it and confirmed that the fuse is operational) or that the thermostat is defective.

[Inspirli]

Do you believe a tank and cap acquired directly from BMW?

Are the aluminium options effective, or should they be avoided?

[Radiantecon]

A minimum of one cap. If yours is absent, you must a replacement nonetheless.

I possess no knowledge about the AL tanks, save from the fact that they are available for purchase. I have never used one.