My heat exchanger / oil cooler is continuing to leak slightly even after the o-rings were replaced twice on my 03 Cooper S.

Finally have a new oil cooler, which I now have after a bit of a wait from Mini.

Does anyone know how much coolant do you lose during this process if you just remove the two lines going in/out of the cooler?

I know the total system capacity is around 6L, but not sure if you lose a liter or two or most of it during this processes.

 

Considering where the feed lines are, probably 40% +/- .

 

About a gallon is my guess. If you get the Genuine MINI stuff, just mix 50/50 with distilled water and you will have 2 gallons. One for extra jobs.

 

Having recently changed out the seals on my 06 Cooper S, I can imagine that fluid line clamps like these Harbor Freight clamps would work a treat. One on each hose and you should be able to limit the coolant lost to just what is in the exchanger itself. I have used these clamps for other (typically fuel related) jobs and they really help limit the mess.

Luckily for me, replacing just the seals fixed my oil leak