Performed the Citric Acid Flush With Great Results

Status
Not open for further replies.
Joined
May 21, 2012
Messages
6,763
Location
Fort Lauderdale, FL
I recently picked up a Kymco People 250 scooter at a steal of a price. It was a steal because the owner rarely rode or paid any attention to it. I wish I would have taken "before" pictures of the thermostat housing, because the whole system was super rusty. Some genius had decided that "you don't need antifreeze in Florida" and put straight water into the cooling system. Electrolysis did the rest. I flushed the system with fresh water for 20 minutes, and that blew out a lot of the loose scale, but the system's surfaces were still super rusty. I remembered that I had purchased some food grade citric acid off of amazon a while ago, so decided to make this my first experiment doing the citric acid flush. Why? I've used the CLR flush to good effect, but do not like how nasty the chemical is, or how hard it is to flush that stuff out when done. Mercedes-Benz is the pioneer of mainstream citric acid flushing, and they only flush out a block for 5 minutes with fresh water after doing a citric acid flush. No baking soda, no nothing. Being a food, it is obviously going to be nontoxic in reasonable amounts as well, and biodegradable. Here's what the inside of the thermostat housing looked like when all was said and done: I replaced the thermostat at the same time, so in order to do a proper "before and after", I took the old thermostat and dropped it in a 10% citric acid/90% water mix for 15 minutes. Mind you, this thermostat was never subjected to flow or heat while it bathed. The rust you see on the thermostat is solid and caked. Not easily removable with a screwdriver. Before: After: Although I did not photograph it, I did inspect the impeller housing interior, as well as the cylinder head water outlet as well. Both were sparkling clean. Nothing to be found at all. Although MB recommends 5 minutes of fresh water flushing after a citric acid flush, I did mine for 15 minutes. My complete procedure? 1. Drain and flush system using Prestone kit for 20 minutes. 2. Drain entire system. (this scooter has a drain plug on the impeller housing that lets it all out) 3. Remove thermostat. 4. Mix a solution of 10% citric acid powder and 90% water. 5. Fill system with solution, and run engine for 15 minutes. 6. Drain and flush system again for 15 minutes. 7. Drain system again, and fill with appropriate coolant/distilled water mix (40% Rotella ELC and 60% distilled, in my case) Official Mercedes-Benz procedure:
Quote:
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
People who do this themselves highly recommend first treating the system with a "Tide flush", using Tide laundry detergent to eliminate any oils that may be present. Eliminating oils is apparently a very critical part of the whole process. You will hear complaints from some that had done the citric acid flush that a component in their system failed during the flush. Like any effective cooling system treatment, any part that is hanging on by a thread will ditch when exposed to a flush. If your system is held together by stop-leak, this will remove it, and leaking will resume. YMMV
 
Joined
Sep 19, 2016
Messages
1,418
Location
Minnesota
Many labels for citric acid for cleaning. I like using water softner cleaner as its reasonable for powder and fantastic for cleaning brass. I seen that the shelf rad cleaner is now citric acid too now. Was a local guy a couple years ago making big bucks selling the stuff as a clothes washing machine deodorizer and mildew remover. I add a shot to the dishwasher and it takes the minor rust color out of the machine.
 
Last edited:
Joined
Oct 9, 2004
Messages
12,564
Location
Cincinnati, OH, USA
Originally Posted By: DoubleWasp
I recently picked up a Kymco People 250 scooter at a steal of a price. It was a steal because the owner rarely rode or paid any attention to it. I wish I would have taken "before" pictures of the thermostat housing, because the whole system was super rusty. Some genius had decided that "you don't need antifreeze in Florida" and put straight water into the cooling system. Electrolysis did the rest. I flushed the system with fresh water for 20 minutes, and that blew out a lot of the loose scale, but the system's surfaces were still super rusty. I remembered that I had purchased some food grade citric acid off of amazon a while ago, so decided to make this my first experiment doing the citric acid flush. Why? I've used the CLR flush to good effect, but do not like how nasty the chemical is, or how hard it is to flush that stuff out when done. Mercedes-Benz is the pioneer of mainstream citric acid flushing, and they only flush out a block for 5 minutes with fresh water after doing a citric acid flush. No baking soda, no nothing. Being a food, it is obviously going to be nontoxic in reasonable amounts as well, and biodegradable. Here's what the inside of the thermostat housing looked like when all was said and done: I replaced the thermostat at the same time, so in order to do a proper "before and after", I took the old thermostat and dropped it in a 10% citric acid/90% water mix for 15 minutes. Mind you, this thermostat was never subjected to flow or heat while it bathed. The rust you see on the thermostat is solid and caked. Not easily removable with a screwdriver. Before: After: Although I did not photograph it, I did inspect the impeller housing interior, as well as the cylinder head water outlet as well. Both were sparkling clean. Nothing to be found at all. Although MB recommends 5 minutes of fresh water flushing after a citric acid flush, I did mine for 15 minutes. My complete procedure? 1. Drain and flush system using Prestone kit for 20 minutes. 2. Drain entire system. (this scooter has a drain plug on the impeller housing that lets it all out) 3. Remove thermostat. 4. Mix a solution of 10% citric acid powder and 90% water. 5. Fill system with solution, and run engine for 15 minutes. 6. Drain and flush system again for 15 minutes. 7. Drain system again, and fill with appropriate coolant/distilled water mix (40% Rotella ELC and 60% distilled, in my case) Official Mercedes-Benz procedure:
Quote:
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
People who do this themselves highly recommend first treating the system with a "Tide flush", using Tide laundry detergent to eliminate any oils that may be present. Eliminating oils is apparently a very critical part of the whole process. You will hear complaints from some that had done the citric acid flush that a component in their system failed during the flush. Like any effective cooling system treatment, any part that is hanging on by a thread will ditch when exposed to a flush. If your system is held together by stop-leak, this will remove it, and leaking will resume. YMMV
That's impressive-which citric acid did you use? The Mercedes, or something else like food grade citric acid? I still have some of the caustic/neutralizer left, but that stuff is pretty harsh & dangerous to work with, not to mention the environmental issues. EDIT:whoops, I missed the "from Amazon" part, I'll look for it there.
 
Last edited:

DoubleWasp

Thread starter
Joined
May 21, 2012
Messages
6,763
Location
Fort Lauderdale, FL
I'm going to re-host them tonight. Apparently, Photobucket now wants $400 a year to allow 3rd party hosting. There's no way I'm going to go along with that.
 
Joined
Jun 28, 2003
Messages
6,638
Location
Illinois
I buy citric acid by the 50 lb bag off ebay to use in my water softener. Works great in the cars cooling system too.
 
Joined
Dec 12, 2002
Messages
43,656
Location
'Stralia
Just an FYI...it's what we use in the power stations to clean the boilers after 4-8 yeas use. (And when I build a 13 tonne liquid CO2 storage system back in 1991, we used citric to clean the copper brazed lines of heat scale...old mate was (allegedly) a chemical engineer, and had a wading pool of citric acid that he "pH" tested by taste)
 
Status
Not open for further replies.
Top