[QB93Z]

I have cleaned and reinstalled stock ZR-1 radiators 3 times and have removed and replaced 4 radiators, 2 DeWitts and 2 Ron Davis.

From my experience. the only way to "clean" a radiator that has blocked air flow is to remove the radiator from the car. The problem that I have seen is fine grit that is lodged between the fins. I have been able to remove most of the grit by laying the radiator flat on a concrete floor, lift it a few inches off the floor and then slamming in down flat against the floor. Do this once and then feel the grit that will be on the floor under the fin areas. Sweep the floor clean and repeat. Repeat until there is no more (or very little) grit coming out of the fins.

Do a before and after visual inspection through the fins looking toward a light or the sun. After the mechanical shock cleaning, you should see a noticeable difference in the air passages.

The first time I tried this method, I had removed the radiator and "cleaned" it with 100psi air blown "through" the radiator. The air cleaning is effective for removing leaves and candy wrappers from the front of the radiator, but proved to be ineffective at removing the grit blocking the air passages.

I would not recommend trying to clean the air passages mechanically because it is very hard to not deform the fins.

Good luck.

Jim