So at random times my car will decide to overheat. usually when i am in a low gear for too long like driving around the college parking lot for 20-30 min finding parking. or sitting in traffic for too long. when i start moving again and upshift the car starts to cool down. since last year i had a same motor swap since my last d16y7 blew. just swapped another one with 90k miles on it. replaced the thermostat and replaced a blown radiator that had a nice crack on it. it has been in a shop for doing all this except the thermostat(DIY) and my guys said it was all good. please tell me any possible things that are going on.

 

First thing to check is if the radiator fan is turning on. Let the car idle for about 15-20 minutes or until it starts overheating. If the fan doesn't turn on by then we can start diagnosing why it doesn't turn on (usually the fan switch).

 

Doesn't sound random to me. Check for air in the system. Bleed it.