And I'm flummoxed!

Firstly, I must state that the bleeding process for the R53 is a horrific design and totally inelegant.

I flushed and changed my coolant and cannot for the life of me get the damn thing bled --- after half a dozen attempts!

I used both bleeders.

I'm still getting bubbles.

I was alarmed and thought the headgasket was going bad. I used a block tester to see if any combustion gasses were present and the fluid remained blue,
so it doesn't seem to be the HG, but I'm gonna re-test tomorrow just to be on the safe side.

I did a pressure test and it held well at 18psi --- only dropped 1psi after about ten minutes.

I also bled the system under pressure and I still got bubbles bubbling up and it's driving me mad!

Where in the hell could air be entering the system????

Any ideas?

Could a bad thermostat gasket allow air in?

Bad oil cooler?

That's the only 2 candidates I can think of outside of the headgasket.

The car is not overheating.

It's a 2006 MCS JCW.

I went into the "secret menu" on the speedo and monitored the temps while I drove it around the block a few times - max was 92c --- I then let it idle in the driveway and waited to see, and at 110c the fan kicked on.

Everything seems fine though and if I wouldn't have happened to see the bubbles I wouldn't be concerned --- the temp gauge remains rocksolid in the middle as always but I've learned after researching this problem that the gauge is set to a wide parameter and not really to be trusted and what some people call the "BMW blinders" as far as gauge accuracy.

Any help or pointers greatly appreciated,
thanks.

 

I may not be of much help. When I service the SC I drained out quite a bit of coolant but I didn't try to flush the system as most people do. I don't see the point of the flushing and think it is a conspiracy of the antifreeze industry.

I didn't had any trouble bleeding the system. I open the plastic bleeder on the top coolant hose and it did nothing to expel air. Bentley manual instruct to set the heat to full on and run the engine at idle. I think this is necessary for the coolant to bypass the thermostat as it is shut when cold. Watch the coolant expansion tank level and keep refilling when it drops. Once the engine warms up it was bled, and I didn't think it did. I drove around the blocks and check the tank and surely the coolant level stays up.

I was shocked as how easy it was.

 

 

pnwR53S -
I bought the car at 99,500 miles and it needed a new coolant reservoir and I changed it out for a black metal tank, and due to the mileage + unknown-to-me history I thought it'd be a good idea to drain the whole system and use fresh coolant. It had regular green stuff in it and quite stupidly (in retrospect) I decided to go back "official" and use the blue stuff so I bought some Zerex G48 -- I feel like a sucker for paying so much for coolant and at this point I'm so bugged out about the bubbles that I'm probably gonna drain and refill again and I'm going back with the regular green stuff while also putting in a new thermostat (mainly due to paranoia about the gasket, but I've also read that the housings can be crappy, should I also get a new thermo housing for peace-of-mind?)

What drew my attention to closely watch my reservoir was seeing the massive splatter spots which easily show up on the top of the black tank, so it seemed to be puking up even if my temp gauge remained rocksolid middle. I had bought a brand new factory cap but I've read that, again, quality can be spotty even with brand new caps and they may not perform as designed due to variance out of spec:

http://www.gtt.uk.com/gtts-cool-guid...ooling-system/



I read on MiniTorque a few of the guys were using Volvo caps and I decided to get one of those.
And indeed, it fixed the puke splatter problem, so I no longer have to sweat that.

The Volvo cap is rated at 1.5 bar (21.7 psi).



AoxoMoxoA -
Many thanks for posting that guide!
The crucial part to my eyes and a step I didn't take is:

Leave BOTH plugs loose so system vents during filling.

So I'm gonna deffo use that technique when I drain and refill.

Seeing that the guide is from a BMW tech, it reminded me of something else ---- that apparently BMW cooling systems are known for airlock problems and being a bitchpig to properly bleed for like the last 20 years according to some of the stuff I read while researching my problem. I dunno if that's true because I have no experience with BMW vehicles, but this experience with my R53 has turned what should be a very simple procedure into a frustrating clustermuck.

 

I'd advocate you stay with the proper coolant; either the actual MINI branded (purchased online or at dealer) or the G48. I believe the MINI branded is actually cheaper than the G48. In any event, those two coolants are designed to work with engines which have both cast iron (block) and aluminum (head) components. The dinosaur green stuff is old school, made for the iron blocks and heads era engines.

Interesting, I just wonder if that extra 6 psi +/- threshold would cause other problems should the cooling system act up. The OE MINI caps are definitely a known failure item though; I'm on #3.

That's what probably caused your issues. I've done it the 'BMW Tech' way, and have never had an issue with the process.

 

I second to use MINI coolant because of the AL and Fe metal combo. If you shop around they can be have at reasonable price and cheaper than overrated aftermarket brands. I would not fuss too much about the accuracy of the expansion tank pressure unless they are way off. My Mini will have some signs of white spots from spattering after a day of hard track driving on hot summer days. Each time I check the coolant lever hardly went down. I also agree with AoxoMoxoA what can happen with + 6 PSI should the thermostat trends too hot.

You did not specifically address if you set the cabin heater full on high. Can the bubbles come from trapped air in the heater core and hosees and just slowly being expelled out?

 

I did have the heater on, yes.

Tomorrow I'm going to re-do the whole procedure using the BMW Tech guide technique that AoxoMoxoA posted --- if I still have bubbles after that, then I'll be really concerned!

Hopefully all will go well.

For now, I've decided to just re-use the G48 as it's only got a couple of thousand miles on it.

As for the +6 psi cap -
Bentley manual states max test pressure for cooling system is 1.5 bar, so I think it'll be okay,
anything above that may cause problems though.

 

This is what I use in my MINI. Typically available at local auto parts stores. BMW # 82142209769 may also be an option.