I'm assuming that since it has the mach 15 it is the rtr. That means the body has already had colling holes cut in it, right? Check that the drive train spins freely, front and rear wheels. make sure the engine isn't covered by essecive dirt. make sure your air filter is clean also check the brake at idle and wide open If all this is good than try a cooler glow plug. Hope this helps and let me know if it does