FSM calculations produce a 2.7 lbs of citric acid in the cooling system according to the volume of water to fill it. However, I'm using the 'bucket and sump pump,' method which will require an additional few gallons of water.

Would using more water for the flush require more citric acid in the flushing solution?

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84 300SD
85 380SE
83 528e
95 318ic

Yes. The acid:water mix sets the concentration. If you add more water without adding more acid, the concentration reduces considerably. The easiest way to measure it, is 1 pound of citric acid to 1 gallon of water. Figure out how many gallons of water you're going to have, add that many pounds of citric acid.

Be sure to rinse very well after the acid flush.

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How convenient. I just happen to have 5 lbs of critic acid, a bottle of Shout and 10 gals of distilled water.

I appreciate your point. I leaned in that direction but had not read any consideration for that even though it fits the FSM. I suppose it's one of those obvious things that I often ignore to my detriment.

Thank you, Sir.

__________________
84 300SD
85 380SE
83 528e
95 318ic

Might consider just dumping the coolant and flushing everything with a garden hose.

If your rad is plugged up with debris, even after backwashing, there’s a chance no amount of citric acid flushing will clear it. I asssime you’re having cooling probs??

Following the proper steps is critical do getting all the crud and solder bloom out ~

First step is to flush with the heater on full until there's no more coolant then refill with the shout and run it a while, also with the heater on full .

Drain and flush again until clean then refill the system using pre mixed citric acid and distilled water, button 'er up and drive for a while, my '82 240D's radiator, heater core and cylinder block had so much solder bloom and rust silt it took a could days of back and forth driving to work before it all came loose .

Be aware that if you don't remove the right side block drain plug you'll never get all the flushing mix out .

Like every other basic service / repair job, YOU will do it best because you care and you won't rush the job .

After the citric acid flush and drain I run distilled water and baking soda to make 100 % sure there's no acid left in there .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Thanks, I've made it though the initial flush with water, the Shout stage and am about to flush the citric acid though the block. I bought a backup radiator new and intend to shoot a light coat of flat black high temp paint on it but I'm excluding it and the heater coil from the citric flush.

With the heater and radiators isolated from the flushing process where should I introduce the acid solution into the engine and where should I hook the return hose for maximum efficiency?

Thanks for the baking soda tip. That's a good idea.

__________________
84 300SD
85 380SE
83 528e
95 318ic

If you don't flush the heater core at the same time you'll be leaving the largest deposits of rusty silt un touched .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

I got paranoid and flushed the heater core alone with water only. I should have replaced it when I had the dash removed rather than freaking out about it now.

If it fails I have plenty of experience removing the dash so it is what it is now.

I finished the engine flush by flushing first with tap water, draining the system including removal of the block drain plug, flushing with Shout and draining including the block drain plug, flushed again with distilled water and drained including block plug then flushed with citric acid and drained it including the block plug. I finished the process by flushing with distilled water and drain everything once again.

The process took nearly a week because I didn't trust the system to hold the pressure produced by the sump pump and monitored the system while the pump was working. Now can find the block drain plug remove it and replace it without climbing under the car.

I removed the hoses and pipe which connects the thermostat housing and heater core and soaked them overnight in citric acid solution and also gave the plastic overflow tank the same bath.

Today I will rinse the hoses and tank then put everything back together, mix the antifreeze, fill the system fire it up and search for leaks. This project is doable but there is a lot of work involved.

Including buying the sump pump the process cost about one hundred bucks.

__________________
84 300SD
85 380SE
83 528e
95 318ic

? Wasn't it fun accessing the block drain plug ? .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better