• My average temps dropped by 5 degrees around town. Big difference was cooling capability on long hills. Probably 15 degree difference.
• Why? Improves coolant contact with the water jacket surface.
• You can buy Citric Acid at your local home brew supply store for about $3.00.
• I went conservative as well and used 1/2 cup acid/gallon of warm water then topped off with water.
• Ran it for about 5-7 minutes with the heater turned off then drained.
• Let it completely cool (3 or so hrs), refilled with distilled h2O....repeated three times with the heater turned on.
• Also drained via the block valve.
• Also should remove the thermostat if you are going to do this because flaked material will probably get caught up in it. I forgot to remove mine (new) on the first drain. Pulled it out and sure enough some debris was lodged in it.
• I've since added "WaterWetter" by Redline. Supposed to also increase cooling surface / coolant contact. Seems to help.
• Currently running 2/3 distilled water & 1/3 MB Coolant.

I'm in Arizona this week and it is hovering around 100 F. A/C blasting on yesterday's drive up to Flagstaff (4,000' climb) at 70 - 75 mph and running between 80C (down hill) & 95C (long steep grades) water temps...

Beautiful. Wasn't that way prior to the flush!

P.S. Don't put cold water in your hot dry motor!!!

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1986 300SDL 440,xxx