Coolant flush question - PeachParts Mercedes-Benz Forum

gorsuchmill · #1 05-01-2007, 01:12 PM

Geoff - I have an 87 300TD, so the block drain location may be different. I drive the car onto ramps and reach the drain from below, crack it loose, then spin it a turn or so with my fingers. It rains as well, but a 3 gal bucket (about the height of a 5 gal bucket cut in two) catches most of the fluid. I also pull the lower rad hose where it connects to the rad, which drains 80%-90% of the total. The lower hose is much faster than the rad drain.

I could add more citric acid, but I'm thinking about flushing it clear and calling it a day. As it stands now, I'll need at least two more flushes just to get it clear again. If I were to do it over, I'd start again with the degreaser, otherwise any residual oils/greases that were never flushed out to begin with would render the supplemental citric acid useless. Agree?

When it's all said and done, if nothing else I would have gotten rid of the nasty green in favor of G-05.

dieseldiehard · #2 05-01-2007, 02:07 PM

Quote:

Originally Posted by gorsuchmill

Geoff - I have an 87 300TD, so the block drain location may be different. I drive the car onto ramps and reach the drain from below, crack it loose, then spin it a turn or so with my fingers. It rains as well, but a 3 gal bucket (about the height of a 5 gal bucket cut in two) catches most of the fluid. I also pull the lower rad hose where it connects to the rad, which drains 80%-90% of the total. The lower hose is much faster than the rad drain.

I could add more citric acid, but I'm thinking about flushing it clear and calling it a day. As it stands now, I'll need at least two more flushes just to get it clear again. If I were to do it over, I'd start again with the degreaser, otherwise any residual oils/greases that were never flushed out to begin with would render the supplemental citric acid useless. Agree?

When it's all said and done, if nothing else I would have gotten rid of the nasty green in favor of G-05.

Glad you are getting rid of the nasty green stuff. On an aluminum head that stuff is risky.

The '87 drain valve has a nipple on it for attaching a hose that can go over to a bucket or whatever, this is one of the small improvements that the 124 has over the 123 which use a PITA threaded plug that usually takes a torch to loosen the first time and a huge hex wrench with a long extension on it. I've lifted the engine off the mounts trying to get one of them loose and finally gave up.

When using the citric acid flush I will drain and refill at least 4 or 5 times, running the engine up to heat (thermostat in) every time, I drive about 1 or 2 miles at 50 MPH to warm it up and the thermostat opens and you feel the heater come on (force it on by setting the control to click in the red and set to defrost) The water should be pretty clear on the last flush and not feel slippery.
Fortunately I only have to do this every 5 or 10 years, in between the other flushes are simple drain and replace coolant (MB only).

pizzachef · #3 05-05-2007, 04:55 PM

Quote:

Originally Posted by gorsuchmill

Geoff - I have an 87 300TD, so the block drain location may be different. I drive the car onto ramps and reach the drain from below, crack it loose, then spin it a turn or so with my fingers. It rains as well, but a 3 gal bucket (about the height of a 5 gal bucket cut in two) catches most of the fluid. I also pull the lower rad hose where it connects to the rad, which drains 80%-90% of the total. The lower hose is much faster than the rad drain.

Okay, that's about what I figured. That's the route I have to take too...its not easy to do 5+ refills and drains in a day. I end up lying in a puddle every time after the first one. Might just drain the degreaser and refill with Zerez and see how it goes.

Thanks for the tip.
-Geoff

oldnavy · #4 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 · #5 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.