Is it not good to put only a low temp fan switch and radiator cap without putting is a thermostat? I have j's racing. Is there any DIY for installing those and a thermostat

 

You don't have to do the thermostat. In fact, if you live in a cooler climate, you should probably leave it off.

Look in the DIY FAQ...there is a DIY for installing the mugen version of those parts.

 

Here in Greece the summer period is awful for our engines. Very hot weather and a lot of traffic. I feel guilty anytime who decide to run my car before afternoon! I was considering the solution of getting the "coolant upgrades" but after reading some posts, i confused myself. Can you please help me? Is it worth for my stock engine to get low thermo, fan switch and radiator cap? Just to know that we run over 35-40 oC outside temp...and we stacking in traffic!
Thank you

 

At least from a street driven perspective here in the SE US where we've been getting close to 100 every day for the past 2+ weeks, this has resulted in 15-20 degree F drop. Highly recommended.

 

how hard/messy is it to change out the thermostat with the car only on jack stands not on a lift?