Coolant flush question - Page 2 - PeachParts Mercedes-Benz Forum

oldnavy · #16 05-05-2007, 06:55 PM

So where do you get the degreaser? This is a new one on me, never heard about that stuff.

I have been looking for the citric acid local, but have about given up. Guess it is the internet.

I haven't looked yet, but does the 2.5L in the '91 300D have a drain valve or is it just a drop the lower radiator hose?

I was planning to remove the green stuff this week or next.

sokoloff · #17 05-05-2007, 08:15 PM

Mercedes sells both the degreaser and the citric acid. The manual says that you must degrease before using the citric acid whether there is evidence of oil in the system or not - at least it says that in my 123 manuals. For degreaser you can use Liquid Tide or dishwasher liquid soap. The citric acid can be found at many places that carry canning supplies or can be ordered from a pharmacy or chemical supply house.

pjc · #18 05-05-2007, 08:43 PM

Based on my own recent experience, to do a thorough job you should plan on the following steps. Note that at each step, you run engine to op temp for 5-10 minutes, with defroster on, then cool before draining. Draining from both the radiator and the engine block plug removes much more than just the radiator, but still leaves at least 1 or 2 litres in the heater core.

1. Drain existing antifreeze.
2. Water and degreaser flush.
3. One or more plain water rinses.
4. 10% citric acid solution flush (100 grams acid per litre of system capacity).
5. At least one plain water rinse (preferably 2-3).
6. Distilled water rinse.
7. Fill with new antifreeze (put in 50% of system capacity in undiluted antifreeze first, then top off with distilled water).

In addition to the old antifreeze, at least the first two flushes/rinses should be considered sufficiently contaminated with antifreeze to be collected and properly disposed of as hazardous waste.

An easy way to help "bleed" the air is to disconnect the top radiator hose at the radiator and pour into that first, rather than just the reservoir tank. That way, you're filling the engine block directly.

And, it should go without saying, this is a good time to check the condition of all hoses, including those going to the heater core, and replace any that are wearing out.

oldnavy · #19 05-05-2007, 11:27 PM

Talked to a friend and he said Shout stain remover was an excellent degreaser and he has used it on his car. He said it took about 1.5 lbs to do his 300D turbo (85?) W123 and that should apply to just about all 300's. I asked the wife where we could get sour or kosuer salt and seems she had a 5lb box in the pantry, so it appears I am good to go for the job soon as I am feeling froggy.

oldnavy · #20 05-06-2007, 06:28 PM

Found some Citric acid today and bought a pound and quarter of the stuff, which was all they had. I have the Shout to degrease with, G05 antifreeze, but I need some distilled water. I guess a midnight run to Wal-Mart is in the works for tonight. If the weather holds I will do the job tomorrow, just don't want to be in the drive-way doing this if it is raining.

I did the rear gear oil change today so that job is out of the way. Got the tranny flushed and new tranny filter & fluid in last Tuesday. All that is left after the coolant job is the brake fluid flush, then the a/c and she will be ready for a run to MI or one of the coasts.