A bad radiator whether clogged or leaking radiator fluid would not directly cause your Lexus to fail the smog check, however it could cause your car's NOx emissions to increase high enough to cause it to fail the emissions portion of the smog inspection.
NO (Nitrous Oxide) is formed when an engine's combustion chamber temperature increases above 2500f. A defective radiator could cause high combustion chamber temps resulting in high NOx.
posted by SmogTips Support
