[Persian Whisperjet]

In anticipation of a preventative thermostat swap (I'm at 101K) I also want to change out the coolant.

My goal is to have the coolant mostly changed with distilled water, then when I do the thermostat I will refill with the BMW coolant to get back to the 50/50 ratio.

The overflow reservoir holds about one quart. Question: If I suction out one quart at a time and replace it with distilled water 5-10 times over the course of a week will that do the trick, or does the same quart of coolant stay in the overflow tank and I would just be changing out the same liquid over and over?

Thanks in advance for any suggestions.

[dmanb2b]

It circulates. When cold, if you take the cap off at idle you should see a nice steady stream.

[335stoner]

it would probably take you a year to change it out that way... on a small scale think about it this way

if you have a quarter gallon of coolant and you take out an ounce of coolant and add water

**to me** the water you added has just become "contaminated" with coolant so the mix ratio would be off and it would take way longer to reach the water and no coolant..

my best suggestion would pull the bottom pan and drain the radiator and fill it with your water run it maybe drain it again then add your 50/50 mix..

living here in Texas I like to run 70w/30c in my cars for the added cooling properties.. ill change mine to this when I do the coolant at some point in the future.

[Persian Whisperjet]

Originally Posted by 335stoner

my best suggestion would pull the bottom pan and drain the radiator and fill it with your water run it maybe drain it again then add your 50/50 mix.

I thought draining the radiator required the intercooler to be moved. Not true?

[335stoner]

good question... I do not know that one.. but the intercooler is super easy to remove

had a mini mod session at my house and one of the members here changed it out in about 30 minutes. it is only held in by two screws

[fsd350]

Originally Posted by Persian Whisperjet

I thought draining the radiator required the intercooler to be moved. Not true?

As I recall I removed the intercooler and the fan/shroud to drain radiator and replace thermostat. I replaced the boost hose seals while I was in there. If you run the distilled water through 2-3 times you should be good. Don't remember, but you may be able to get at 1 of the block drains also. If so make sure you replace the crush washer. Adding coolant full strength when the block is full of water and radiator drained should put you right at 50/50. Make sure you spend a little extra time bleeding the system when you refill.

[TDIwyse]

I did something like this method (can't see the pics anymore due to photobucket a-holes) which drains most of the coolant, is very quick and simple, and doesn't require removing the intercooler: http://www.e90post.com/forums/showthread.php?t=551742

[Yozh]

^^^ That is exactly what I did.

[supermann125]

This is great. Just standard coolant or does BMW have some Prestone they've rebadged and called their own?

[montr]

Originally Posted by supermann125

This is great. Just standard coolant or does BMW have some Prestone they've rebadged and called their own?

I use Pentosin or OEM BMW coolant
https://www.napaonline.com/en/p/AOR8114117

[Persian Whisperjet]

Thanks to all, plan worked perfectly. After pouring two gallons of distilled water into the car one quart at a time over the past week (evacuating the overflow tank after each drive) I raised the car and dropped the pan, then unhooked the trans heat exchanger hose, whereupon a gallon of coolant came out, plus another quart when I unbolted the actual thermostat.

I have no EGR, so the swap was straightforward but I would have been absolutely lost had someone not warned me to undo the 10 mm bolt holding the hard plastic heater return hose. Unbolting that bracket gave me the ability to flex the return hose. See pic.

I added a gallon of coolant and some water and that was that.

In looking at the Torque logs I see this (OEM) thermostat runs a tiny bit cooler than the original one--87 versus 89 degrees.

[fsd350]

Originally Posted by Persian Whisperjet

Thanks to all, plan worked perfectly. After pouring two gallons of distilled water into the car one quart at a time over the past week (evacuating the overflow tank after each drive) I raised the car and dropped the pan, then unhooked the trans heat exchanger hose, whereupon a gallon of coolant came out, plus another quart when I unbolted the actual thermostat.

I have no EGR, so the swap was straightforward but I would have been absolutely lost had someone not warned me to undo the 10 mm bolt holding the hard plastic heater return hose. Unbolting that bracket gave me the ability to flex the return hose. See pic.

I added a gallon of coolant and some water and that was that.

In looking at the Torque logs I see this (OEM) thermostat runs a tiny bit cooler than the original one--87 versus 89 degrees.

Glad it went well. I still have the EGR cooler on mine (blocked)
Mine runs around 87c also since replacement a couple years ago