Looking for advise on an issue with a 2007 E92 335i Car had the low coolant...

Looking for advise on an issue with a 2007 E92 335i. Car had the low coolant light go on. Didn't see any visible leak so I topped it off with bmw coolant and put a new genuine cap on the coolant res. Car has had water pump and reservoir replaced in the past year. Continued to drive it and noticed a large puddle under the rear center of the engine one day after I parked it for a while and coolant light back on. I've pulled the belly pan off and let the engine run for over an hour and cannot get it to leak... Any ideas guys? Is it possible its blowing it out of the reservoir after I park the car and it cools down? Purchasing a pressure test kit soon and going over it again..

%d comments
  • Mine leaks where the core meets the plastic start there look for residue have seen a few posts of res having cracked

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  • The res was replaced recently so I don't believe that is the cause of the issue. When I replaced the cap I did notice some milky sludge build up on the underside of the coolant cap.. I'm wondering if you maybe the oil cooler gasket or oil filter housing gasket is allowing oil into the coolant and pressurizing the system etc causing these mysterious issues? Car is just at 100k miles now..

  • Interesting stuff. I think your on to it!

  • Out of the 10,000 members here no one had any issues with the cooling system or insight to provide? Any help would be greatly appreciated.

  • Pressure test kit sounds like a good idea... saw this on youtube which might be of help .. https://www.youtube.com/watch?v=4AB1RbAYbVA

  • No reason to waste money on a pressure testing kit.

    Get the car to full operating temp of 240.

    Then let it idle with the heat off for 10-15mins. System will pressurize itself fully and reveal the leak

  • This is probably not it, but want to share anyway. I got my alternator replaced and there is a hose that literally clips on which was not seated in all the way - and I was loosing radiator fluid. All that needed to be done is to push the hose in until it clips in. Don't do this when the car is hot - you can burn yourself.

  • Was the classic thermostat to water pump hose, the plastic part broke. Best part is I have documentation for it being replaced 6 months ago.. hose looks older then that, I think the shop forgot or f*cked him.

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  • Typical shop bullshit