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Last early summer I flushed my radiator with CLR. Flushed repeatedly with water.
But since then, I have replaced the water pump and last week a radiator. Both leaking within 9 months.
Was it the CLR? Who knows, but I sure won't ever use that "trick" again.
Only upside is I went to a 4 core radiator from a 3 core. That change has done more than anything - water wetter, 40 below, low temp fan switch, and on and on. Temp just sits at the 180 degree mark now.
I actually talked to a rad shop last year about using clr and he said he tried it himself. Left it overnight and it didn't do anything to remove the build up. Now at that time he wouldn't know if it did any long term damage or not. What he said works best is baking soda. What I did last year was just kept emptying the system and putting in fresh water and running it for a day and changing it again. Did this over a period of 4 days untill nothing icky was coming out. Worked great. Also took the rad out and flushed it with hosemany times. So try the baking soda. :auto:
I tried this once many years ago on an old '81 Cutlas. I drained the rad and refilled with fresh water topped it off with CLR, left it over night and flushed it in the morning. I didn't run the engine with the CLR in the rad since I had no idea how it would react to heat. It cleaned it up not too badly(not great either), but the rad lasted another couple of years with no problems. And yes my middle name is Bubba.
:conehead