Thanks Azinn. But since I don't have a record of when it was changed last and the truck has about 225K miles on it, I'd like to drain as much of the old coolant as possible. Still looking for the radiator drain.

Is it on the bottom of the radiator or on the front near the bottom?

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They say its on the bottom. After going out and looking a my radiator I sure don't see it. I would think pulling the lower hose and putting a hose with running water running through the radiator for a few minutes would do a good job of flushing out all of the old coolant. My 2 cents.

don't matter, the drain plug and the lower radiator hose are in the same position, one in front and one on the back. You will drain out the same amount regardless of turning the plug or pulling the hose. There will be a quart or 2 of fluid left in the engine block. unless you open the block drain, which is another PITA to get at.

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98 ML320 (gone but not forgotten)

It faces the front of the vehicle, over on the right side (passengers side), it is almost always red plastic. It is hard to turn, but you turn it 1/4 turn ccw and then pull it out, towards you. CAN be done with a brush guard, makes it even worse though.
Use MB coolant or Zerex G05, which the big box stores usually have.
Gilly

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Photo of drain plug in this thread Swapped radiator on 2001 ML430

I finally got around to replacing my coolant in my 99 ML 320. I could not see the drain plug through any opening in the bumper. The one farthest to the passenger side is blocked by some hardware that looks like it secures the plastic bumper to the car. The drain is directly behind that opening. You can see past the tow hook in the second opening in the bumper, but the drain is no where near that. Here is what I see when I look:

[IMG][/IMG]

So took off the right tire and I could see the drain from the rear right side. I could barely get my fingers on it. I worked with some long needle nose pliers and a small pair of vice grips to turn the drain CCW from the side. I believe I had to turn it a full 360 degrees before I could pull it out.

Here is a shot of the drain from the right front tire well:


It took 10 or 15 minutes to drain. Closed the drain with the same tools. Then I added 7 quarts Zerex G05 and 2 quarts water through the overflow tank on the firewall while running the engine. This took another 15 or 20 minutes. I squeezed the upper radiator hose occasionally to try to get the air to rise up into the tank.

I was expecting to be able to add more water, but evidently I left close to 3 quarts in there since I didn't take out the block drains.

Thanks for everyone's help.

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