Mobolaji Zubair

My Audi 2008 v6 quattro loses coolant rapidly I have Chuka cked for leaks and found none however I recently changed my rafiator .... Its fustrating as I have to top the coolant twice in a day!!!!!!! It runs fine but shows coolant twice a day especially when I am in a bit of traffic I also observe the engine begins to jerk when stuck in traffic for a while and it shows coolant

N_Jay

Check to see if it is spitting coolant when hot (maybe a new cap)

Check the oil for signs of coolant (Maybe even get an oil analysis)

Check the compression for a blown head gasket.

SloopJohnB@mac.com

is often the source of problem. Was the vehicle losing coolant before the radiator replacement? If so, this could be a lot like the dude asking the doctor if he could play the piano after his operation and the doctor said sure and the guy said that would be great because he couldn't play it before!

Chances are the radiator replacement didn't cause the coolant loss but if you're loosing coolant with no leaks visible it's 'possible' there is a pinhole leak that only shows up under pressure. I had such a leak on an old Saab 900Turbo that drove me nuts until I pressurized the system and saw the tiny leak..it sprayed on the hot engine and evaporated before it hit the ground.

It's also possible the engine was overheated (perhaps that's why you changed the radiator?) and warped such that a head gasket has failed.

In any case, you should pressurize the system with any one of a variety of pressure testers which may help find the leak. You can also use a combustion leak detector system that either sniffs the coolant at the expansion tank for HC (if you have an emissions detector, LOL) or one that aspirates gases above the coolant in the expansion tank through a test fluid. Google combustion leak detector.