On the 3rd-gen Tacoma the thermostat is not up on top of the engine — it sits in the water inlet housing at the lower front of the block where the lower radiator hose connects. That means the real work is draining the radiator, pulling the plastic under-cover (and skid plate if you have one), and working on your back with coolant dripping on you. The fasteners themselves are two small bolts or nuts, and the whole thing comes apart in ten minutes once you can see it.
What varies is access. The 3.5L 2GR-FKS is more crowded around the front crossmember and lines, so a 1/4 in drive ratchet and a stubby wrench earn their place. The thing people get wrong is the refill: this system holds air, and just pouring coolant into the reservoir leaves you with a no-heat heater and a temp gauge that swings. Use a spill-free funnel at the radiator neck, run it with the heater on full hot until the fan cycles, and re-check the level cold over the next few days.
| Item | Type | |
|---|---|---|
| Floor jack 2 ton minimum Lift the front of the truck to reach the water inlet from below. | Required | shop |
| Jack stands 3 ton pair Support the frame rails while you work under the front end. | Safety | shop |
| Wheel chocks Block the rear wheels before lifting. | Safety | shop |
| Socket set 10, 12, 14 mm, 3/8 in drive Removes the engine under-cover / splash shield and skid plate bolts (10 mm and 12 mm most common, 14 mm on some skid plate hardware). | Required | shop |
| Ratchet, 1/4 in drive with extensions 3 in and 6 in extensions The water inlet housing bolts are small and in a tight space; 1/4 in drive fits best. | Required | shop |
| 10 mm socket 10 mm 6-point, 1/4 in drive Water inlet (thermostat housing) bolts/nuts on 2GR-FKS and many 2TR-FE builds. | Required | shop |
| 12 mm socket 12 mm 6-point, 3/8 in drive Some 2TR-FE water inlet studs use 12 mm nuts; also used on shield and bracket bolts. | Required | shop |
| Stubby ratcheting wrench set 10 and 12 mm For the housing fastener you cannot reach with a socket behind the hose. | Recommended | shop |
| Hose clamp pliers Spring-clamp / constant-tension type Releases the factory spring clamp on the lower radiator hose without fighting it. | Required | shop |
| Flat-blade screwdriver Medium, plus small pick Pops the plastic radiator drain cock, frees clips and breaks the hose loose from the neck. | Required | shop |
| Drain pan 6 gal / 24 qt low-profile Catches the 2-3 gallons of coolant that come out of the radiator and hose. | Required | shop |
| Funnel and short hose 3/8 in ID hose Directs radiator drain-cock flow into the pan instead of over the crossmember. | Recommended | shop |
| Spill-free funnel kit Universal with Toyota radiator neck adapter Fills and burps the system without airlocks — this engine is fussy about trapped air. | Required | shop |
| Gasket scraper / plastic razor Cleans the aluminum sealing face without gouging it. | Required | shop |
| Torque wrench 1/4 in drive, 20-200 in-lb Housing bolts go into aluminum and are low torque; overtightening cracks or strips. | Required | shop |
| Torque wrench 3/8 in drive, 10-80 ft-lb Reinstalling skid plate and shield hardware to spec. | Recommended | shop |
| Thermostat with gasket OE Toyota 90916-03153 (2TR-FE) / 90916-03151 or 03152 family (2GR) — confirm by VIN The replacement unit; always use the new rubber sealing ring supplied with it. | Parts | shop |
| Toyota Super Long Life Coolant Pink SLLC, pre-mixed 50/50; ~2 gal for 2.7L, ~2.5-2.75 gal for 3.5L Refill; Toyota pink is the correct chemistry — do not mix with green or orange. | Consumables | shop |
| Distilled water 1 gal Top-off and flushing the reservoir without adding minerals. | Consumables | shop |
| Replacement hose clamp Worm-gear, fits lower radiator hose Optional backup if the original spring clamp has lost tension. | Consumables | shop |
| Shop rags and brake cleaner Clean coolant off the sealing face, crossmember and belt area. | Consumables | shop |
| Nitrile gloves and safety glasses Coolant drips straight down onto your face and hands on this job. | Safety | shop |
| Infrared thermometer or scan tool OBD2 with live coolant temp Verifies the new thermostat opens and the gauge/ECT reading is normal after refill. | Recommended | shop |
2GR-FKS 3.5L: water inlet housing uses two 10 mm-head bolts, and access is tighter around the front crossmember and A/C lines. 2TR-FE 2.7L: the same housing, but depending on build year it may use 12 mm nuts on studs instead of 10 mm bolts — have both sizes on hand. Coolant capacity differs too: roughly 8-9 quarts for the 2.7L versus about 10-11 quarts for the 3.5L, though a drain-and-refill only replaces 2-3 gallons.
| Water inlet / thermostat housing bolts or nuts (2TR-FE and 2GR-FKS) | approx. 7-9 Nm (65-80 in-lb) — verify in the service manual |
| Radiator drain cock | Hand-tight only, do not use a tool |
| Engine under-cover / splash shield bolts | approx. 29 Nm (21 ft-lb) for 12 mm-head bolts — verify in the service manual |
| Front skid plate bolts | verify in the service manual |
| Wheel lug nuts (if wheel removed for access) | 113 Nm (83 ft-lb) |
Housing fastener sizes are 10 mm on the 2GR-FKS and 10 or 12 mm depending on build year on the 2TR-FE, so check with both before committing a wrench; treat the housing bolt torque and skid plate values as approximate and confirm them against the Toyota service manual for your VIN.
It is in the water inlet housing at the lower front of the engine, driver's side, where the lower radiator hose bolts on. You reach it from underneath after removing the plastic engine under-cover, not from the top of the engine.
Buy two gallons of Toyota pink pre-mixed Super Long Life coolant for the 2.7L and two to three for the 3.5L. A drain-and-refill through the radiator drain cock only takes back 2-3 gallons, not the full system capacity.
The spring side goes into the engine and the small jiggle/bleed valve goes at the top, roughly 12 o'clock. Match the orientation of the unit you removed, and line up any notch in the flange with the housing.
No. The Toyota thermostat comes with a rubber sealing ring that seats in the block; sealant will make it leak or contaminate the system. Just clean the aluminum face and torque the two fasteners evenly to about 65-80 in-lb — verify the figure in the service manual.