Decided to give the citric acid flush a shot in my recently acquired 2003. My usual method is to drain and fill 3 or 4 times with not very good results usually.
What I started with.
After draining the coolant, I installed a dummy thermostat I cut the center out of, and a 3/8 NPT ball valve on the block drain to make it easier for me to open and close it all the time. I can only access the left side block drain unfortunately which leaves some of the capacity in it. Book capacity is 4.8Gal and after draining both taps I can get about 2.5 gallons back into it, the rest being in the heater core and right side of the block.
Then I flushed it for about 10 minutes with both drains open at 2500rpm. I didnt have a flushing Tee, I just stuck the hose into the coolant tank which seemed to work fine.
Closed the drains, dumped about 2 lbs of citric acid powder into in and filled it up. Closed the cap. I ran it for a bit more than 5 minutes, again at 2500rpm, at which point it was up to 190F and starting to spit out the coolant cap.
I ended up letting it sit for about 20 minutes while I ate dinner before I drained it.
Stuck the hose back in and filled it, ran it about 10 minutes at 2500 with the taps open again.
Then I let it idle while I dumped 10 gallons of distilled through it. I wanted the remaining water in the system to be distilled or close to it.
Removed the ball valve, reinstalling the plug and took out my dummy thermostat for a new one. I also popped a core plug and installed a block heater.
What was most impressive to me was it actually managed to clean the coolant tank. I thought I was going to have to replace it to be able to see through it again. But its fine. There isnt I huge amount of flow in there so I thought it wouldn't do a very good job.
To fill I added 2 gallons of straight G05 and then topped up with 50/50. I also added RMI while I was at it. Ill test the concentration later this week, but it should be in the ballpark.
Bonus shot of the inside of the block after I popped the core plug out. This was post flushing.
What I started with.
After draining the coolant, I installed a dummy thermostat I cut the center out of, and a 3/8 NPT ball valve on the block drain to make it easier for me to open and close it all the time. I can only access the left side block drain unfortunately which leaves some of the capacity in it. Book capacity is 4.8Gal and after draining both taps I can get about 2.5 gallons back into it, the rest being in the heater core and right side of the block.
Then I flushed it for about 10 minutes with both drains open at 2500rpm. I didnt have a flushing Tee, I just stuck the hose into the coolant tank which seemed to work fine.
Closed the drains, dumped about 2 lbs of citric acid powder into in and filled it up. Closed the cap. I ran it for a bit more than 5 minutes, again at 2500rpm, at which point it was up to 190F and starting to spit out the coolant cap.
I ended up letting it sit for about 20 minutes while I ate dinner before I drained it.
Stuck the hose back in and filled it, ran it about 10 minutes at 2500 with the taps open again.
Then I let it idle while I dumped 10 gallons of distilled through it. I wanted the remaining water in the system to be distilled or close to it.
Removed the ball valve, reinstalling the plug and took out my dummy thermostat for a new one. I also popped a core plug and installed a block heater.
What was most impressive to me was it actually managed to clean the coolant tank. I thought I was going to have to replace it to be able to see through it again. But its fine. There isnt I huge amount of flow in there so I thought it wouldn't do a very good job.
To fill I added 2 gallons of straight G05 and then topped up with 50/50. I also added RMI while I was at it. Ill test the concentration later this week, but it should be in the ballpark.
Bonus shot of the inside of the block after I popped the core plug out. This was post flushing.
Last edited: