good evening,

i am replacing my coolant pump that failed in the midst of a citrus flush. most concerning to me is that the pump is covered in white chalky deposits. the monovalve was also clogged with this stuff. just caked on.

its not citric acid powder - it must be a precipitate or byproduct of the citric flush.

anyone experience this? or is this normal and what the flush is cleaning out?

i put in food grade pure citric acid, and followed the same steps as posted here a while back. im perplexed.

many thanks,
dd

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

This info is kind of disturbing. Not a normal condition I hope.....

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

Sounds like you used too much citrus or you didn't get the engine hot enough.

Ok so this isn't normal to the people who have done a citrus flush.

I used exactly 2 lbs of food grade citric acid I got from a local homebrewing supplier. I got the car up to its normal 87 C on the highway. After about 20 miles I lost heat (monovalve plugged up with this stuff) and when I started the car the next morning the waterpump was weeping so it needed to be replaced. When i dumped out the acid from the block/radiator it's milky colored with a solid powder suspended in it. When I took out the waterpump it was caked with the stuff, and same with the monovalve.

As I said, I followed all the flush steps as outlined in the archives and done successfully by others.

Im just hoping someone can shed some light on what the hell is going on and how I can fix it. It's getting cold here and I need to get antifreeze in this thing. As said Im still perplexed...

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

Not sure if this is part of your problem at all, but did you deoil the system before doing the citric acid flush? Manual is very specific in saying that you must deoil before using the citric acid whether there is evidence of oil in the coolant or not.

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Len
'59 220S Cabriolet-SOLD and living happily in Malta
'83 240D 351,500 miles original owner-SOLD
'88 560SL 41,000 miles - totaled and parted out
https://sites.google.com/site/mercedesstuff/home
'99 E300 turbo 227,500 miles
'03 SLK320 40,000 miles - gave to my daughter
'14 Smart electric coupe 28,500 miles
'14 Smart electric cabriolet 28,500 miles
'15 Smart electric coupe 28,000 miles

Good point - but Yes. I ran through half a cup of powdered tide (as described here) which I dissolved in water and then dumped in. Maybe I should have used liquid, or more of it.

I am going to do some experiments with the citric powder I have left to see if I can make it turn into the same stuff on a lab bench by adding oil or heating it or something.

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

Last year, when my coolant overflow tank started leaking, I got a sort of white chalky, milky film all over everything, and it wouldn't flush cleanly, unless I scrubbed it. I mean, regular water pressure alone wasn't enough to wash it off.
It dried, and then in order to remove it, I can take a wash cloth and just plain water, and rub it off, and it will come off.
A couple of months ago, when I drained my radiator, ran some water from the outside hose through the upper radiator hose (a lame attempt to flush the system), and some of the coolant dripped on engine parts, it too left this white residue, which, although easily cleaned by the method I described above, still made me question just what I have running through my coolant system. I drained all I could, replaced the coolant recovery tank, then added some Water Wetter and Orange antifreeze, but I am considering to do a Citric acid flush when it comes Spring time.
I did one years ago, to my 1979 240D, purchasing the citric acid crystals from the Mercedes Benz dealer, but with all of the posts about citric acid eating away at the water pump, causing leaks, etc., I'm kind of worried about using it, and perhaps my Orange coolant and Water Wetter is enough.
What do you all think - is the risk of things going wrong worth flushing with the Citric acid crystals? By the way, when I purchased this 1983 300D 7 years ago, I installed a brand new radiator, as it got a little too hot for my liking, and the car had set for ~ 2 years before I purchased it. I have never had a problem overheating, and don't really want to mess up a good thing by doing the Citric acid flush. What do you all think?

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1983 300D (Hans)

dd--

i had this exact condition on both of my cars which i was flushing this summer/fall. steps i followed were:

1) drain coolant (mine were both green)
2) wash twice with water
3) flush (with about a ~25 mile drive, at the minimum) with degreaser--i used 16 oz shout
4) wash twice with water
5) load the 1 Kg citric acid, predissolved in hot water, and run for >50 miles (in the case of the wagon, ~60 miles, in the case of the sedan, ~200 miles); the wagon clogged badly with this white chalky stuff, which i thought might be "scale," but i don't know what scale looks like. (on the wagon, the thermostat lower hose sprung a huge leak due to the pressure with the clog.)
6) wash the wagon with ~10 water washes to get chalk out; the sedan was probably washed ~20 times--this is with running the engine between washes
7) fill with 50/50 deionized water and zerex antifreeze

it's been about two-three months since the flushing was complete, and i haven't had any problems since; i was impressed by how shiny the radiator inside was on the wagon, but on the sedan it's visibly corroded--i didn't check either before the flush, unfortunately...

i also had to bypass the servos on both cars; for the wagon, i did this after the zerex fill and so some chalk remained around these hoses, which were badly kinked... i'm planning another flush next spring.

anyway, you're not alone with the chalk...
-noah

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1980 300D (non-turbo, 421k miles)
1984 300TD (turbo, 305k miles)
1985 Vanagon (170k miles)

Yes! Im not alone!

Question - what kind of citric acid powder did you use and did you ever verify that it wasn't the problem?

Did you have your t-stat in during these washes, or did you take it out?

Did you get a LOT of this crap? Its good to hear it CAN be washed out, even if it takes 20 washes. I find it hard to believe this was sitting in my cooling system previous to the flush. If it was, holy cow...

dd

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

Im going to start de chalking this thing tonight...in the cold NE night. Sweet!

If I take the thermostat out and drive around, would I be able to get it up to 80C like the FSM suggests for when doing a flush? Or would I never climb past 40 or 50?

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

With stat out you probably won't be able to maintain normal engine temps. Cover the radiator with cardboard but keep an eye on the temp gauge so you don't overheat.

__________________
85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I used citric acid from a soap supply shop here in Seattle, Zenith Supplies (www.zenithsupplies.com). I used it on both cars with the same result--maybe it was the citric acid, but I figured citric acid is citric acid is citric acid...

Yes, I had just installed new thermostats prior to the flushes.

I'd say it was a LOT of crap, yes--the wagon clogged several times before it finally started flowing freely. Not as bad on the sedan, though. I was draining into a oil change pan and still saw cloudiness for a good five washes or so *after* getting the bulk of the crap out.

I didn't have overheating issues before the flush, so I'm not sure the chalk was present, or if it was some sort of reaction with the citric acid.

Good luck and stay warm!
-noah

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1980 300D (non-turbo, 421k miles)
1984 300TD (turbo, 305k miles)
1985 Vanagon (170k miles)

For all who have been reading along...

Yesterday I flushed the system. Concurrently I mixed a 10% solution of citric acid and ran some experiments on it. I:

-heated it to boiling
-added some motor oil to it
-added some antifreeze to it

All of this with the same tap water that I got the white chalk with. No chalk, nothing created the precipitate.

CONCLUSION: The white chalk was IN the system to begin with. So, to test my hypothesis I ran another shot of citric acid solution in the radiator, following the FSM directions. Ran it up to 80C for five minutes as described in the FSM and drained. Trace amounts of white stuff, but the water was brown and had a bad smell. Point is the white stuff didnt re-occur. So the citrus flush got it all out, and it was in there to begin with.

What caused it? I found during the flush my monovalve had a tear and my aux pump wasnt working. My car is front Texas and heat was rarely used. So Im guessing between those things there was just a lot of gunk buildup in the core etc.

So hopefully I can finish the flush with dignity this week. I had to replace during the flush (that I didnt know about before)-

-water pump (weeped after day 1 of flush)
-radiator (neck snapped off)
-aux water pump (dead)
-monovalve diaphram (discovered this unclogging)
-expansion tank (saw a crack near the cap)

good luck and be ready for detours...
dd

__________________
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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

RFDillon, I hope it was the gold Zerex-G05 you are using, not the Deathcool orange/high mileage type....

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

99 W210 E300 Turbo Diesel, chipped, DPF/Converter Delete. Still needs EGR Delete, 232K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Gone and still missed...1982 w123 300D, 1991 w124 300D

it's like dumping acid in your engine

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1987 420 sel