coolant temp rises as i step harder on gas pedal
 

o well first off when i bought my car (1992 LS400 5 days ago) it ran below the middle point. right on the 2nd line i believe. when i would floor it, the temp would rise up and then go down to the first mark/line. after flooring it, when i let go of throttle, it would rise back up to 2nd line. now after i took it in for the power steering pump and tensioner belt/pully replacement, my temp is up at the middle point (in between 2nd and 3rd line) and sometimes right above it (right below 3rd line). when i give it more gas than usual, it would rise up then slowly back down. i dont even have to floor it, just gas it pretty hard and it will rise. what can cause this to happen? i would like to run as i did when i bought the car at the 2nd mark/line.

flush the coolant and replace the thermostat

whats a good brand thermostat

that sounds like your fan clutch is broken, as you step on the gas the fan clutch is suppose to pull up closer to the radiator, sometimes it gets old and breaks, if you going to change that, you might as well flush the radiator and replace the thermostat, I would suggest OEM lexus parts

fan clutch isnt as common as a shop forgetting to top off coolant.

OEM thermostat or TRD thermostat are both good choices and can be had relatively cheaply if ordered through Carson Toyota aka L-tunedparts.com

Thats the first thing I would do. At least the stat if the coolent is still good.

fix. low coolant and prev. owner ran no thermo. stuck one in and was fine.