On the XV70 Camry the thermostat is not a five-minute part. It lives in the water inlet housing at the lower front of the engine block, so you have to get the car in the air, drop the plastic undercover and drain the radiator before you can touch it. The fasteners themselves are ordinary 10 mm hardware and the swap takes minutes; everything around it is what eats the afternoon.
The part that catches people out is the refill. This engine family holds air easily, and a system that looks full can still have a pocket sitting at the thermostat. Use a spill-free funnel, run the engine with the heater on full until the fans cycle, and recheck the reservoir cold the next morning. Also get the jiggle valve at the top — installed upside down, the thermostat will trap air and you will be chasing a temperature swing you just created.
| Item | Type | |
|---|---|---|
| Floor jack 2 ton minimum Raise the front of the car to reach the undercover and water inlet. | Required | shop |
| Jack stands 2 ton pair, under pinch weld/subframe points Support the car while you work underneath. | Safety | shop |
| Wheel chocks Block the rear wheels before lifting. | Safety | shop |
| Socket set 10 mm and 12 mm, 6-point, 3/8 in drive Engine undercover bolts (10 mm) and water inlet housing fasteners (10 mm); 12 mm for some splash shield and bracket bolts. | Required | shop |
| Ratchet and extensions 3/8 in drive, 3 in and 6 in extensions, swivel joint Reach the housing bolts past the subframe and hoses. | Required | shop |
| Trim clip / panel removal tool Plastic pry set Pop the push-pin clips holding the engine undercover and air deflectors. | Required | shop |
| Drain pan 2 gallon low-profile Catch coolant from the radiator drain and the lower hose. | Required | shop |
| Hose clamp pliers Swivel-jaw spring clamp pliers, cable type preferred Release the factory spring clamp on the lower radiator hose in a tight spot. | Required | shop |
| Hose removal tool / pick set Break the hose loose from the inlet neck without tearing it. | Recommended | shop |
| No-spill coolant funnel kit Universal spill-free funnel with Toyota adapter Fills and burps the system without repeated air pockets. | Required | shop |
| Torque wrench 3/8 in drive, 20-200 in-lb range Housing bolts thread into aluminum and are low torque. | Required | shop |
| Gasket scraper / plastic pick Non-metallic Clean the sealing face without gouging the aluminum. | Recommended | shop |
| Shop towels and brake cleaner Clean the mating surface and wipe coolant spill off the subframe. | Consumables | shop |
| Thermostat with seal Toyota 16031-25010 (A25A 2.5 / hybrid) or 16031-31020 (2GR 3.5) — confirm by VIN The replacement unit; always fit the new rubber O-ring supplied with it. | Parts | shop |
| Coolant Toyota SLLC pink, pre-mixed, approx. 1-2 gallons Refill; do not mix with green or orange coolant. | Consumables | shop |
| Distilled water 1 gallon Rinse spills and top off if using concentrate. | Consumables | shop |
| Nitrile gloves and eye protection Coolant is toxic and hot coolant can scald. | Safety | shop |
| OBD2 scan tool Live data capable Watch coolant temperature during the bleed and confirm no P0128 after. | Recommended | shop |
Fastener sizes are the same across the generation: 10 mm for the water inlet housing, undercover and most brackets. The 2.5 L A25A-FKS and the hybrid A25A-FXS share the same thermostat housing layout and the same part number family (16031-25010); the 3.5 L 2GR-FKS uses a different thermostat (16031-31020 family) in a housing that is slightly more open but sits behind the fan shroud ducting. Hybrids additionally have a separate inverter coolant loop with its own reservoir that is not touched by this job.
| Water inlet / thermostat housing bolts or nuts (10 mm head) | approx. 78 in-lb (8.8 Nm) — verify in the service manual |
| Radiator drain cock | hand tight only, plastic |
| Engine undercover bolts | approx. 78 in-lb (8.8 Nm) — verify in the service manual |
The 10 mm fastener size, lower-front water inlet location and pink SLLC requirement are consistent across the XV70 range; verify the exact thermostat part number by VIN and confirm the housing torque figure in the Toyota service information before final tightening.
It is in the water inlet housing at the lower front of the engine block, where the lower radiator hose attaches. You reach it from underneath after removing the engine undercover, not from the top of the engine bay.
Roughly 1.5-2 gallons total system capacity depending on engine, but a radiator drain only recovers part of that — plan on about 1 gallon of pre-mixed Toyota SLLC pink for a thermostat job, with a second jug on hand.
You do not remove the radiator, but you do have to pull the lower radiator hose off the inlet neck to get the housing off. A spring clamp plier makes that far easier in the tight space behind the subframe.
That code means the engine is not reaching operating temperature fast enough — usually a cheap aftermarket thermostat with the wrong opening temperature, a unit stuck open, or one installed with the jiggle valve misoriented so air is trapped against it. Use the genuine Toyota part and re-bleed the system.