Cooling System Questions: W123, 617

I want to change the coolant on my 1981 and 1985 300D's (617 engine) and I have a few questions.
1. Is there a brand and type of coolant that I can purchase at an auto store for this engine or do I need M-B coolant.

2. Engine drain plugs...is there a picture, diagram, etc. of where the drain plug(s) are located?

Thanks, in advance

[gsxr]

Zerex G-05 coolant is identical to the Mercedes stuff, a light yellow/gold color (not green, orange, or blue.) It should be available at most McParts stores for about half the cost of the genuine MB stuff. Also read this article:

http://www.w124performance.com/docs/mb/other/antifreeze_article.pdf

[sailor15015]

You can either get the MB coolant from this site or the dealer, or you can get Zerex G-05 at your local McParts, if you can find it. Several people have had luck with it but I've been to seven different parts stores and have yet to see it. I just used the green stuff with the intent of doing a thorough flush every couple of years. The engine drain plug is located on the passenger's side, about one or two o'clock from the starter. Crawl under there and look up. It'll be the only 19mm bolt right by the starter. Be careful when removing, however, because you'll probably get wet before you can scramble out of there. Have you considered a citric acid flush? I'm finishing up one now and its amazing how much crap came out of there.

Originally Posted by sailor15015

Have you considered a citric acid flush? I'm finishing up one now and its amazing how much crap came out of there.

I am not familiar with this, but I am interested.

[sailor15015]

Drain the old coolant and flush three times with tap water to get it all out, allowing the engine to cool completely between each flush. Add a non-foaming degreaser(Shout) to remove any oil in the system. Run for at least half an hour, on the road not just idling. Again, repeat the cool/flush/run three times again. Now add anywhere from a pound to a kilo of citric acid, pre-disolved in hot water to your cooling system. Take a good vigorous drive, about an hour should be good. Again, cool/flush/refill/drive but it'll probably take a lot more than three times if your system is really dirty. The reason I did this is because I had to replace my water pump and I got a look at how rusty it was in there. Before I started, the inside of my block drain plug was pretty rusty, now it looks like clean metal.