E46Fanatics - View Single Post - DIY Radiator Flush
View Single Post
Old 03-27-2012, 04:34 PM   #19
Registered User
Join Date: Mar 2012
Location: california
Posts: 2
My Ride: BMW 325CI
When you drain the radiator, the coolant inside the engine block (3.5 Lt approx) does not come out of the radiator drain plug.
I think you should not flush it if you re not draining engine block.
If you flush it with water without draining the engine block, what happens is that the water you pour in will displace the coolant inside the engine block and when you add new coolant into the system with the 50/50 mix, that will become 25/75 mix (75% water and 25% coolant) when it mixes with the water sitting in the engine block.

That may have caused the fan to blow even when the engine is off because the higher proportion of water in the coolant system makes it to vaporize faster which creates high presure inside.

BMW Antifreeze/Coolant (50/50):
1 Gallon (3.78 Lt) of concentrated coolant, when you mix it with distilled water becomes 2 Gallons (7.56 Lt). BMW Service Manual says the exact volume to cover engine block and radiator is 8.4 Lt (for most models), so I guess it's good to have an extra bottle of coolant.

Engine-Block Drain Plug Location:

Radiator Drain Plug Location:

Last edited by rajivsinghsuwal; 03-30-2012 at 11:09 AM.
rajivsinghsuwal is offline   Reply With Quote