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1995 E320 Wagon, 2002 S430
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Discussion Starter #1
Does anyone know the precise recipe for MBs citric acid cooling system flush? The proper citric acid to water ratio and how much citric acid they use on an M104? I also understand they pre flush it before doing that to remove any oily residue so as to not render the citric acid flush ineffective. Anyone know what they use to remove oily residue in their pre flush routine? Really curious to know as this method is supposed to be the gold standard for cooling system and radiator flushes, restoring radiators to almost like new internally (heater cores too not to mention) and restoring the systems ability to keep the engine cool. Have read many posts where folks claim this flush brought their temps down almost 10 degrees C in some cases (radiator must have been badly loaded with scale). Anyone?

Thanks.
 

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About a dozen 1988, 1989, 1990, and 1991 sedans, wagons, 4Matics and 1 coupe
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I bought 2 bottles of the MBZ flush a few years ago. p/n A 000 989 10 25 The bottle contains 0.5 kg/1.1 pound of "citric acid powder." There are no instructions with the stuff, just a symbol showing that you should get instructions in section 20 of the service manual. So i did.

The first surprise is that MBZ indicates that this solution and procedure are specifically for diesel engine cars. Don't know why.

The text indicates that the cooling and heating system can be cleaned with a 10% citric acid solution.

20-015 tells you to:

Drain the cooling system of all the old coolant
Remove the thermostat and replace it with a "forcibly-opened" thermostat p/n 000 589 63 00
Connect a flushing connection pipe (a tee) p/n 117 589 00 90 00 between the upper radiator hose and the radiator
Connect a tap water hose to the tool fitting
Open the surge tank cap
Set the heater to defrost on cars with automatic CC so the aux coolant pump runs
Start the engine and run it at 2500 RPM
Open all drain plugs and turn on the tap water to maintain a full cooling system at all times while the engine is runniing
Flush for 5 minutes to remove all old coolant
Shut off engine, shut off tap water, and allow cooling system to fully drain
Install radiator and crankcase drain plugs
Dissolve citric acid powder in 5 liters of water
Fill cooling system with solution and top off with water, bleeding as necessary
Install surge tank cap and start engine
Run engine for 15 minutes at approximately 2500 RPM and blip throttle occasionally
Make certain that coolant is flowing through radiator and heater core.
Open cooling system drains again and turn on tap water to flush cleaning solution from cooling system
Start engine and run at 2500 RPM for 5 minutes to flush all cleaning solution from system
Shut off engine and remove special tool from upper radiator fitting
Reinstall normal thermostat
Make sure that all drain plugs are installed and tight
Remove the surge tank, flush it separately, and reinstall it

???
Install a modified surge tank with silica element p/n 124 500 17 49 or 124 500 18 49 according to which diesel engine is installed in the vehicle
???

Fill with fresh coolant/water mixture, bleed system, start engine, and check for leaks
 

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1995 E320 Wagon, 2002 S430
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Discussion Starter #5 (Edited)
Excellent detailed instructions -- super huge thanks for takign the time to dig that up -- it should help many.

It talks about using a forcibly opened thermostat -- I wonder if you could just use a t-stat gasket in its place. The question is whether or not the gasket would stay put all by itself and whether or not it would seal up properly.

The conversion then is 1.1 lbs of citric acid to 1.3 gallons of water to mix it up initially... then you are adding water on top of that (not distilled water as this is just a flush). So it's really 1.1 lbs per the entire cooling capacity of the engine which is roughly 9.5 quarts (around 2.4 gallons).

In summation...

flush old cooling system with garden house and kit for 5 minutes to get all residue out

mix 1.1 lbs citric acid powder to 1.3 gallons of water and add to engine, adding water on top of that until cooling system is full

Run for 15 minutes at 2500 RPM

drain

flush with engine running at 2500 with hose running and attached with drains wide open

Seal everything up and refill with coolant and distilled water
 

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'92 300TE 4matic 280,000miles, '92 300TE 4Matic 'Ice Blue Metalic' 101,000miles
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Excellent detailed instructions -- super huge thanks for takign the time to dig that up -- it should help many.

It talks about using a forcibly opened thermostat -- I wonder if you could just use a t-stat gasket in its place. The question is whether or not the gasket would stay put all by itself and whether or not it would seal up properly.

The conversion then is 1.1 lbs of citric acid to 1.3 gallons of water to mix it up initially... then you are adding water on top of that (not distilled water as this is just a flush). So it's really 1.1 lbs per the entire cooling capacity of the engine which is roughly 9.5 quarts (around 2.4 gallons).

In summation...

flush old cooling system with garden house and kit for 5 minutes to get all residue out

mix 1.1 lbs citric acid powder to 1.3 gallons of water and add to engine, adding water on top of that until cooling system is full

Run for 15 minutes at 2500 RPM

drain

flush with engine running at 2500 with hose running and attached with drains wide open

Seal everything up and refill with coolant and distilled water
augapfel is da man once again for information.:thumbsup: I used all kinds of commercial flushes after I replaced my head and I don't think any of them did a very good job. I'm going to try this in the Spring with citirc acid powder.:bowdown: I'm a licensed plumber, so I'll make the tap tee out of spare copper and a garden hose fitting...will be fun! I've even got a spare upper hose that was the wrong configuration, but the correct ID...use a piece of it.

Kevin
 

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About a dozen 1988, 1989, 1990, and 1991 sedans, wagons, 4Matics and 1 coupe
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As far as I can tell the only variable for the DIYer is the citric acid powder strength. Note that the SM indicates a 10% citric acid solution. What does that say about the MBZ powder? Is is normal strength? Not being a connoisseur of citric acid powder I have no idea of what products are out there and their strengths.
 

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'92 300TE 4matic 280,000miles, '92 300TE 4Matic 'Ice Blue Metalic' 101,000miles
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As far as I can tell the only variable for the DIYer is the citric acid powder strength. Note that the SM indicates a 10% citric acid solution. What does that say about the MBZ powder? Is is normal strength? Not being a connoisseur of citric acid powder I have no idea of what products are out there and their strengths.
Yeah well, I won't be looking for a substitute....just pay for the MB product and follow the SM instructions. I don't know if the products I used were even citric acid based....they were all liquid premixes.

Kevin
 

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1996, A124, E320 Sportline Cabriolet x 2
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For the M104 MB tell me not to use the citric acid flush. Can this be true??
 

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'92 300TE 4matic 280,000miles, '92 300TE 4Matic 'Ice Blue Metalic' 101,000miles
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From what I've been able to gather; one kind of flush attacks corrosion inside the cooling system. Another kind of flushing compound attempts to flush out residual oil in the cooling system (like from a bad HG).

It was my understanding that the MB specific, citrus flush was aimed at flushing out corrosion within the cooling system.

Why did they tell you not to use the MB citrus flush in a m104...because you're after oil residue?:confused:

Kevin
 

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1996, A124, E320 Sportline Cabriolet x 2
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No it wasn't that Kevin, at the time I was looking to have the cooling system made more efficient, temps were getting up a bit and the normal things had been replaced. What they said was that MB do not recommend a Citric Acid flush for the M104. But I didn't ask why.......
 

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'92 300TE 4matic 280,000miles, '92 300TE 4Matic 'Ice Blue Metalic' 101,000miles
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Aside from adding another cam, more timing chain, different head and a different fuel management system, the m103 & m104 are very close in mechanical design.....which puzzles me as to why anyone in MB circles would advise against using MB's own citrus flush in a m104....:confused:

Kevin
 

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1989 500 SE, 1995 E280,1997 Chrysler Grand Voyager 3.3 V6
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Aside from adding another cam, more timing chain, different head and a different fuel management system, the m103 & m104 are very close in mechanical design.....which puzzles me as to why anyone in MB circles would advise against using MB's own citrus flush in a m104....:confused:

Kevin
I remember someone over in the W126 section once did this by the book as above.... he left the acid in too long and it blew out his engine core plugs, so best not to leave it in there too long.
 

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Aside from adding another cam, more timing chain, different head and a different fuel management system, the m103 & m104 are very close in mechanical design.....which puzzles me as to why anyone in MB circles would advise against using MB's own citrus flush in a m104....:confused:

Kevin
Anti-corrosion coating applied to the block apparently. Citric Acid will remove this. Can anybody confirm this please - and I'm talking trained MB Tech. :surrender:
 

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'92 300TE 4matic 280,000miles, '92 300TE 4Matic 'Ice Blue Metalic' 101,000miles
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Anti-corrosion coating applied to the block apparently. Citric Acid will remove this. Can anybody confirm this please - and I'm talking trained MB Tech. :surrender:
Ohhhh....very interesting! Maybe Clark will weigh in on this.

Kevin
 

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I don't recall hearing about a special coating but this is what WIS say's about
flushing in the case of a contaminated cooling system.

"Fill with a 3% solution of water & alkaline cleaner part# 001-986-2171"
Run to operating temp then for additional 10 minutes.

Drain & flush with water. This I would do with distilled water.

Hope this helps.

The citric acid may be diesel specific, I'll check on that.

Update:

From what I can tell citric acid is for rust/corrosion which if you have that any
protective "coating" has failed anyway. I don't see a problem using the MB citric acid.

The alkaline part number is for oil residue like from a failed head gasket.
 

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Thanks for that Clarkz,

Is there anything in there about using Citric Acid for cleaning out corrosion products, or is it just referring to oil contamination?
 
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