2010 Prius IV 167K

I’d definitely do engine water pump, and thermostat; water pumps have been reported failing here, around 150k miles. And the thermostat not much, $30~40 USD iirc.

also consider inverter water pump replacement, sometime. Main issue though, it’s very difficult to remove, apparently you HAVE to remove inverter, no way around it. See video #28 here:

Nutz About Bolts Prius Maintenance Videos | PriusChat

With 167k miles, the timely EGR-cleaning ship had long since sailed. My 2 cents: cleaning is needed at least every 50k miles, to keep it operating as intended, and avoiding head gasket failure.

I’d do it, ASAP, but don’t kid yourself, head gasket may let go, before long.

The EGR cooler will be a bear, I’d consider sodium hydroxide (or potassium hydroxide) solution, JUST for the cooler. With appropriate safety precautions. One end hole of the cooler is ~21mm ID. Plug with #4 stopper, pour in solution (about a cup) prop in corner of laundry sink for about an hour, rinse and repeat as needed.

For the rest, EGR valve, pipe between EGR valve and intake manifold, AND the intake manifold (has EGR passages), brake cleaner, brushes and rags, will be effective enough. Also, the aforementioned caustic solutions will be damaging for anything not 100% stainless steel. So basically, just use it on the cooler.

again, EGR cleaning now is a case of better late than never, but I’d start reading up on head gasket replacement.

more info in my signature. (On a phone turn it landscape to see signatures)