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Old 05-02-2003, 10:18 AM
Registered User
Join Date: Jul 2002
Location: Dallas
Posts: 330
New coolant flush method?

After driving my car for six months with green coolant I am ready to get that stuff out of there. I searched the forums for procedure. General consensus is to pull the drain plug from the block under the manifold between cylinders 5 and 6. I couldn't see the plug from from on top, so I went ahead and called the local dealer. They were more than nice. Said pulling the drain plug can be a job trying to reinstall since it is a little difficult to access. Advised since I am going to change the t-stat and flush to do the following:

Drain the radiator and remove the stat.

Replace the housing without replacing the stat.

Detach the heater hose coming off the rear driver's side of the engine and flush from there. (I guess I would fashion a connection to attach the garden hose so that the pressure from the hose pushes the water through the engine. )

Also said I could flush back the other way and flush the heater core.

Do you guys advocate this method of flushing? A buddy of mine doens't understand how this will get all the coolant out of the block.
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Old 05-02-2003, 11:07 AM
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Join Date: Mar 2003
Location: Southern California
Posts: 2,010
The green stuff is not good. It provides good corrosion protection, but the inorganic salts used for corrosion inhibition precipitate out a lot of deposits. Your aluminum radiator core won't corrode through. It will just clog up. Mercedes antifreeze is formulated with an organic inhibitor package that, according to my research, is very similar to Dexcool, and since Dexcool is available through the aftermarket at reasonable prices (Havoline Extended Life) I use it in all my cars. When replaceing green stuff with an organic inhibitor antifreeze the system should be thoroughly flushed to remove all traces of the green stuff.

After draining, thoroughly flush the system by cold flushing both ways through the heater inlet circuit through the nipple/hose at the back of the head. The drain valve at the lower end of the block on the exhaust side is reachable with a crescent wrench or socket. Lossen it, then attach about a 3/8" piece of hose to the nipple and route to a pan. Then hand turn the valve about one full turn until coolant starts to drain. Mercedes makes it very simple to drain the coolant on the inline sixes without making a mess. The radiator drain valve (behind the removeable cover on the valence panel) is also set up to accept a drain hose.

Once it's thoroughly cold flushed, fill it with water and operate the engine until the thermostat opens and a few minutes after that. Then drain, and if the effluent is colorless and tasteless, you're ready to install an organic inhibitor antifreeze. If not, repeat the process

It's not necessary to remove the thermostat.

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Old 05-02-2003, 11:48 AM
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Join Date: Jun 2001
Location: San Francisco, CA
Posts: 3,096

Thanks for this description. Very helpful.

Your use of "tasteless" is of a concern as anti-freeze, even in small quantities can cause severe renal (kidney) problems.

I would suggest warning against any oral exposure to it and as a side note, pets seem to like anti-freeze. I lost a pet this way. Never leave out where any animals could taste it, even for a minute or two.

'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)
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Old 05-02-2003, 11:56 AM
Posts: n/a
The block drain is no problem when accessing from underneath. You don't need to remove it, you only loosen it a turn or so and it will drain, then tighten it. It is not used as a removable plug.

Good luck,
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Old 05-02-2003, 12:31 PM
junior member
Join Date: Oct 2001
Posts: 592
over the years i have used i believe the prestone backflush kit available anywhere. install a fitting in the proper heater hose, connect the gargen hose and let it rip.
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Old 05-02-2003, 12:51 PM
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Join Date: Jun 2001
Location: So Cal
Posts: 124
I installed Prestone reverse flushing T fitting to heater hose of all my cars since 1980 and flush the coolant of every car every 2 years without remove the drain plug from engine block.
'00 E430 Brilliant Silver/Ash
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Old 05-02-2003, 12:57 PM
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Join Date: Mar 2003
Location: Southern California
Posts: 2,010
Originally posted by haasman
Your use of "tasteless" is of a concern as anti-freeze, even in small quantities can cause severe renal (kidney) problems.
I'm not suggesting making a cocktail out of it, just dip your finger into the effluent and touch it to your tongue, then spit. By the time you've flushed enough for there to be no color, it's likely tasteless, but this test is optional.

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