Faulty Cooling System (Help Needed) - MINI Cooper Forum

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post #1 of 4 (permalink) Old Aug 11th, 2014, 08:41 PM Thread Starter
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Faulty Cooling System (Help Needed)

My JCW lost a bit of water the other day, onto the exhaust manifold causing a bit of steam. I have pressurized the system to see if the expansion tank was cracked or any other sort of leak was involved. It held high pressure for a long time so was assured it wasn't the tank to blame.

Tonight I have changed the thermostat as I took the bleed screw out of the top hose and it was empty. I removed the housing and changed the stat and put it all back together.

I took both bleed screws out, and filled with coolant, kept filling until there were no air bubbles visible at the bleed screws. I then topped up the expansion tank to max and let the car idle up to temp.

There were no leaks so I assumed the job went okay. Water was then rising out of the expansion tank. I drained a bit off then a few minutes late, it rose again. Checked the top hose bleed screw and it seemed empty again????

Is this the head gasket failing and pressurising the water system or could it be the water pump not circulating the water?? Both seem plausible to me :/

Any help is greatly appreciated before I pay for expensive tests/checks.

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post #2 of 4 (permalink) Old Aug 11th, 2014, 11:09 PM
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Bleeding all air out of Mini cooling systems is essential and sometimes time consuming but can give the appearance of a blown head gasket but usually it is air locks.......make sure the heater is full on when bleeding and blows hot air afterwards.....cool heater means air or low coolant level which lets in more air.....many threads on bleeding procedure if you search Mini2.

Water pump can fail on R53 JCW as the water pump is driven off supercharger via gears which can wear.

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post #3 of 4 (permalink) Old Aug 12th, 2014, 06:31 AM
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When I drained & refilled mine on the first run no coolant was circulating & once it gets hot it will start rising & bubbling in the expansion tank if you have an air lock. I let mine cool again then when I started it next time I gave it a few good revs I could then see the water flowing through the small hose into the expansion tank as the coolant started circulating & the level dropped I could then see the air coming through as it was flowing. Mine seemed like it was airlocked around the waterpump area until I got it flowing again. While its running make sure the small top pipe to your expansion tank has coolant flowing through mine wasn't on idle until I gave it a few good revs then once it started flowing it carried on flowing on idle. I am rubbish at trying to explain things so I hope you understood that ok. I also had nothing at the bleed screws until I managed to get it flowing again
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post #4 of 4 (permalink) Old Aug 13th, 2014, 12:59 PM Thread Starter
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Pat on the back for you guys!!! Bloody system still full of air. Thanks a lot!!!
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