First post, but with the help from the forum I was able to flush and add new coolant to my '99 PreRunner with 143,000 miles.
While I was in there, I also changed the thermostat and I noticed the new part has the jiggle valve closer to the center than the old one. I just lined the valve up where the old one was (12 o'clock position). Not sure if this matters or not, there are no leaks, dash temp gauge reads normal during any type (city/hwy) of driving.
The only thing that is off a bit is that I now have a slight vibration I can feel in the entire cab.
The engine idles at ~700-750 RPM at temp, and like other post I have read, stops when taken out of gear, and no noticeable vibe while driving or in motion.
A week before the new coolant/TS, I had the spark plugs (NGK), wires, and fuel filter replaced and throttle body cleaned.
Thanks for any hints or suggestions.