So a little background - It's summer here in Hawaii so my AC is on anytime I'm in the car. I also had my radiator replaced ~6 months ago and my coolant level is fine and has been since bring replaced.

A couple weeks ago I had just finished driving 25 or so minutes home and my AC was working fine. I stopped to get gas, and once I turned my car on and started to drive away there was a loud hissing sound and a big puff of white smoke/mist coming from my engine bay that lasted about 10 seconds. I know what burning coolant looks like since my radiator busted a while ago (why it needed to be replaced) and I know that wasn't it. It also had a kind of sweet smell, so I figured it was R134. My AC was not blowing cold after this, and my car started to run hot. Not dangerously hot - just hotter than normal to where my fan stayed on for a few minutes after turning the car off.
I took the car into a well respected car AC shop here a couple days later since I didn't wanna have to diagnose and fix a leak myself (I figured it was a ruptured line at the time), and the guy said it still had pressure, so it wasn't a burst line. He refilled the system to the correct pressure. AC was blowing ICE COLD after that.

Fast forward to yesterday, I was leaving the house to get gas again, and on the way there I had the same thing happen.

I don't want to keep refilling the system as a temporary fix, I want to fix the root cause of the problem. I've done some searching and can't find anything Mini specific but some other cars that have this happen are purging off extra pressure, possibly have a bad AC clutch?

Anyone have any insight into what might be possibly causing this?

 

I am intrigued. I don't think our cars have anything like safety valve to release the pressure (in fact, I don't think ANY car has it, simply due to ecology reasons). So, my first question would be: did you locate there that 'puff' is coming from? Is it from one of the charging ports? Then you might need to replace valves there. Parts #6 and 7: https://www.realoem.com/bmw/enUS/sho...diagId=64_1119

 

I haven't been able to locate where the puff is coming from as it only lasts for a few seconds and then it's gone. Not nearly enough time for me to pop the hood and run out to open it, especially considering the car was in motion lol. But I also haven't been able to recreate it.

 

Ryaaan
I'm guessing you've got a pin-hole or a worn O-ring on a pipe somewhere that only becomes evident under the highest pressure, which may be at start-up. I think escaping freon would leave some evidence, like ice or water, for a few moments.

 

There should be an oily stain where the blast is landing. Clean the hell out the bay and lower frames so you can find it. Possible seal on the compressor shaft.

 

Greetings.

My 2005 r53 did the same light explosion under the hood last year..and the hissing sound lasted approximately 10 seconds. I did notice an oil coating with a metallic substance sprayed onto the lower passenger side of the engine. I don't have a temperature gauge (navigation) so I never know if the car runs warm. It ended up being the compressor. The service facility needed to replace the entire a/c system,,,as the metallic( polluted) coolant likely leaked into the dryer and the other components.

The cost was $3500.

Best,

Mark

 

Maybe have your AC&R guy inject dye with the next filling, wait for it to do its thing, then look for the massive leak with the cool yellow glasses?

 

There is a blow off valve so to speak on the front undr side of compressor. My wifes r50 did this too never figured out why just pulled the fuse.

 

So I've got a minor update:
I went to go replace my lower engine mount today and noticed a few things:
1. My AC still has a charge. I was going to try to recharge it and it still said it was in the OK range, so I know that's not a problem.
2. I had some oil leaking. I already had a minor oil leak but seems like more has been leaking since I just changed my oil last week and cleaned up the oil that was leaking before.
3. Coolant has been leaking. I noticed a small puddle in my splash shield on the passenger side, and my coolant level was low. My coolant level has been good for a while since I just replaced my radiator not too long ago.

I'll have to take a look into this and see if that fixes it.

​​​​​​​I had some coolant and oil in the engine bay on the passenger side slightly outboard of the oil pan. I already had an oil leak but haven't had coolant leak since I changed the radiator so I feel like I may have been wrong and it might have been coolant purging out. I'll take a look into the compressor shaft seal

That's what I'm afraid of. Do you remember if you had coolant coming out as well as the oil? I haven't done a test yet to see if the compressor is working but I feel like it might have something to do with it since my ac is still blowing hot even when charged.
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​​​​​​​Thanks for the responses everyone, I'm going to continue looking into this and I'll keep updating the thread as I go.

 

I had the same thing happen on a couple of my cars....the blow off valve is down on the compressor....and I'm willing to bet that your radiator cooling fan is not working correctly...when at idle or very low speed, the fan should come on when the compressor clutch engages, if it doesn't come on, your AC system will build up enough high pressure and it will purge that pressure via the valve. The radiator fan keeps air moving through the AC condenser at ide to keep the pressures down at a normal level. Your fan has two speeds, either one or both are not working

Bryan