Ok so I ordered 2.2 pounds of citric acid, I have 16 Oz of Shout, and I have some MB coolant.

Really all I need to know is how many Oz I need to pour into my cooling system before I run my car each time.

Currently I am going to drain the radiator, drain the block (does this plug have a washer that needs replacing?), refill with the shout mix (how much water?). Idle for 10 minutes, drain and flush until it is not soapy anymore.

Then I am going to mix 2.2 lbs of citric acid with warm water (how much warm water?) and pour it in the expansion tank? Should I fill the radiator with water too?

Then Im going to drive for 60 miles, drain the block and radiator, pull all of my hoses and flush with a garden hose. Fill with distilled water and drive and flush 3 times.

Then I will fill with a 50/50 coolant mix, burp the system by parking on a incline, opening the overflow cap and turning on the heat while idling for how long?

This all sound good? Really the only thing I am not clear on is how much water to put into the system, I dont want to put too little in...

Thanks!!

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1985 300D (CA, 173K)

Dynamite Biodiesel Co-op, Phoenix,AZ

Just mix with warm water in a gallon bucket add to system and continue adding warm water until system is full.IMHO, I am not so sure I would drive 60 miles on a citric acid mix with an unknown system. I ran my car for 15 minutes max and then drained, rinsed etc. Better safe than sorry as many on this site have reported problems after aggressive treatment - both my diesels were treated this way with no problems, but again, I was being very conservative -too much too long can dissolve weak metals, careful -

please report back with your results.

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2009 E320 Bluetec 117,000
1995 E300D 306,000 Sold
1996 Ford Taurus LX 130,000 Sold
1985 300TD Still 225,000 Sold
2016 Ford Fusion 24,900

How does 2.2 lbs become 6+ lbs?

where do you get citric acid?

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What Would Rudolph Do?
1975 300D, 1975 240D, 1985 300SD, 1997 300D, 2005 E320 , 2006 Toyota Prius

OJ, not of the Simpson variety...

Sorry, I'll go away now...

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My occupational hazard bein'
my occupation's just not around...
1980 300SD
1980 300SD

That's not all you need to know. Flushing with citric acid is risky business. I would follow the FSM instructions to the letter. Even then, I would not expose my heater core to citric acid. Radiators are easy to replace; heater cores are not.

As tango mentioned, risky. What are you trying to solve? If it's a radiator problem, have the radiator ultrasonically cleaned and tested out of the car, if just basic gunk in the system try the detergent method.

Acid eats alkali metals as soon as it contacts them (aluminum et al), especially in the presence of less anodic metals (such as a massive amount of iron surface area). It doesn't wait 60 miles, not even 10-15 miinutes, it starts right away. If your heater core is marginal, it might not survive the treatment, or if it is still good, you're removing critical metal and shortening its life. If you don't need acid in the system then don't do it.

There is a lot that some mild detergent or even a good water flush can accomplish.

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Gone to the dark side

- Jeff

• My average temps dropped by 5 degrees around town. Big difference was cooling capability on long hills. Probably 15 degree difference.
• Why? Improves coolant contact with the water jacket surface.
• You can buy Citric Acid at your local home brew supply store for about $3.00.
• I went conservative as well and used 1/2 cup acid/gallon of warm water then topped off with water.
• Ran it for about 5-7 minutes with the heater turned off then drained.
• Let it completely cool (3 or so hrs), refilled with distilled h2O....repeated three times with the heater turned on.
• Also drained via the block valve.
• Also should remove the thermostat if you are going to do this because flaked material will probably get caught up in it. I forgot to remove mine (new) on the first drain. Pulled it out and sure enough some debris was lodged in it.
• I've since added "WaterWetter" by Redline. Supposed to also increase cooling surface / coolant contact. Seems to help.
• Currently running 2/3 distilled water & 1/3 MB Coolant.

I'm in Arizona this week and it is hovering around 100 F. A/C blasting on yesterday's drive up to Flagstaff (4,000' climb) at 70 - 75 mph and running between 80C (down hill) & 95C (long steep grades) water temps...

Beautiful. Wasn't that way prior to the flush!

P.S. Don't put cold water in your hot dry motor!!!

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1986 300SDL 440,xxx

Based on what I read here, and by doing a google search for other sources, when I was replacing the rad in my 1980 300td last summer I put my citric acid back on the shelf and just did flushes with mild detergent, then over and over with water, until things ran clear.

The stuff I read did not fill me with optimism for doing the acid flush on a car of that vintage.

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

Wow some really good posts here. Thanks a lot guys. I guess I am reading the wrong threads here because I took my plan directly from old posts :O

Thanks a lot! I will do a very mild citric acid flush, 1lb for 10 or so minutes.

So dont let anything into the heater core? Mild detergent? I assume it is very dirty in there, my heat did not work for years (I assume) until I recently replaced the monovalve.

Also how do you fill these cars radiators? Fill from top hose until you cant fill anymore? And then fill expansion tank to "fill line" (right over the sensor plug)?

__________________
1985 300D (CA, 173K)

Dynamite Biodiesel Co-op, Phoenix,AZ

I've had my '90 300D less then a year. The PO wasn't terrible but he wasn't very good when it came to caring for the car. So I'm going through and doing a thorough job.

I flushed my system about 2 weeks ago. I used distilled water for everything. Pure water is an amazing solvent.

First I drained what was in the system, then I filled it with tap water, ran the vehicle on the road for 10 minutes or so with the heater on high. Then I came home, emptied the system and filled with distilled water and a commercial citric product (I'm not saying is better then using the pure crystal as you are, I'm just saying what I did) and drove it for 15 minutes with theater on high as per the instructions on the bottle. Then I came home, flushed the system and filled it a second time with distilled water and one bottle of the commercial citric flush, drove for 15, etc.

I then filled the system with distilled water, drove for 15 minutes with the heater on, drained, refilled, drove and drained. The water coming out at this point should be very close to neutral, pH ~7. If in doubt see if you can find some litmus paper or better yet universal indicator paper. if you know a lab guy let him test your pH if concerned. But two good flushes with distilled water (powerful stuff) after driving will clean it up.

Then I drained again, partially filled with distilled water, added Purple Ice (similar to Wetter Water) and added enough quality anti-freeze (designed for aluminum systems) to obtain a 40% AF/Water ratio. I live in the SF Bay area so the 40% mixture is fine, maximum protection is around 60% but the system will run cooler at the lower concentrations of anti-freeze.

This is much more thorough then most will do and probably then is needed. I've got the tools, I usually know what I'm doing (yeah right) and I like having high confidence it's done right. I sold my last MB diesel at 400K (miles) and I'd like another 250K out of this one. There are a lot of experienced people on this board and many of their comments are valuable so I'm not claiming to have the best answer.

Finished tonight, added one gallon of G05, sjh, you ever have any corrosion problems with this low of an anti freeze concentration?

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1985 300D (CA, 173K)

Dynamite Biodiesel Co-op, Phoenix,AZ

I've only had the car 8 months and the PO replaced the radiator recently.

As an educated guess I suspect that whatever additives the companies use that they are both buffered and over-designed.

I suspect that even at 10% AF the system would have an adequate amount of beneficial additives.

Recently there was a thread where someone mentioned testing for the acceptable presence of some AF additive by measuring the resistance to ground by sticking your meters probe into the water/AF mixture and having the other probe connected to the block.

He said it was in the FSM.

Please realize that I am giving you my best estimate and recollection and that I know something about some of the chemistry of these systems but not the specifics of AF design.

Anybody who claims to know more (besides some basic concept that I'm sure about) almost certainly does.

It is nice to be done and have good confidence that the car is in good shape.

Later.