in regards to being clean and open for good air flow? Several times over the last 12 years and 264K miles on my 94TT I've seen signs when it would want to overheat on hot days with the AC on. Each time the problem was resolved for several years by removing the radiator and taking about 1/2 day to clean out all of the fins of debris that stops the air flow through the radiator (I would also use an air hose or take the radiator to a coin-op car wash and spray water through the radiator). The same goes for the AC condensor; if it is clogged it won't allow good air flow through to the radiator (and I did the same for the oil intercooler the last time I cleaned it all up).