My SC300 radiator cap has all this stuff that collects on the radiator cap, and im sure goes through out the entire engine. Anyone know what this is? Should I replace radiator as i was going to put a fan shroud.

I should mention that sometime my car randomly overheats on hour long trips.....

Currently driving my RX7 while I wait for replies.

Pics.

 

Is that rust ? Hoping your cooling components system is not rusty in some areas.

A fan shroud can help cool your engine / coolant on the radiator better. That is , if your fan clutch is in good shape (guessing that you have stock clutch fan and not electric fans). Regardless stock or electric fans , there is a reason why you need a fan shroud so put it in otherwise car manufacturers wouldn't have installed one in the first place.

 

It's not rust, it's more like collected junk. Car was purchased without fan shroud, fan clutch was replaced 1 year ago due to overheating within 10 minutes of driving.

 

I would start simple and add the shroud, the whole point of it is to have the fan pull air through the AC and radiator to help cool your engine and make the AC colder. Otherwise just driving wont give it enough airflow and will most definitely cause overheating. If this has been happening for a long time then the heat cycling will likely warp your head and cause a blown head gasket which would be the much worse reason why you are seeing junk on the radiator cap and overheating. Let us know man.

 

I would flush the radiator out with something like Prestone flush. Looks like someone may have used some radiator stop leak in the past.