Originally Posted by sjh

I've had my '90 300D less then a year. The PO wasn't terrible but he wasn't very good when it came to caring for the car. So I'm going through and doing a thorough job.

I flushed my system about 2 weeks ago. I used distilled water for everything. Pure water is an amazing solvent.

First I drained what was in the system, then I filled it with tap water, ran the vehicle on the road for 10 minutes or so with the heater on high. Then I came home, emptied the system and filled with distilled water and a commercial citric product (I'm not saying is better then using the pure crystal as you are, I'm just saying what I did) and drove it for 15 minutes with theater on high as per the instructions on the bottle. Then I came home, flushed the system and filled it a second time with distilled water and one bottle of the commercial citric flush, drove for 15, etc.

Then I drained again, partially filled with distilled water, added Purple Ice (similar to Wetter Water) and added enough quality anti-freeze (designed for aluminum systems) to obtain a 40% AF/Water ratio. I live in the SF Bay area so the 40% mixture is fine, maximum protection is around 60% but the system will run cooler at the lower concentrations of anti-freeze.

I'm sharing what I did. I had my reasons but there are a lot of experienced people on this board and many of their comments are valuable.