On the 10th-gen Accord the thermostat is not in the upper hose where many people look for it. All three powertrains put it in a housing on the lower front of the block where the lower radiator hose lands, so the job is really a coolant drain plus dropping the plastic under-tray, then two small bolts. Tool-wise it is cheap: 10 mm and 12 mm sockets, a couple of extensions, hose clamp pliers and a funnel kit.
What varies is access. The 1.5T gives the most room, the 2.0T has more plumbing in the way, and the hybrid demands you disable the high-voltage system first and know that its electric coolant pump can cause the same symptoms as a bad thermostat. The mistake people make is the refill — these engines trap air readily, and skipping a proper burp with a spill-free funnel and two fan cycles leads to an overheat scare on the first drive and a false conclusion that the new thermostat is bad.
| Item | Type | |
|---|---|---|
| Floor jack 2 ton minimum, low-profile Lifts the front of the car to reach the under-tray and lower hose. | Required | shop |
| Jack stands 2 ton pair, under front subframe jack points Supports the car while you work underneath. | Safety | shop |
| Wheel chocks Blocks the rear wheels with the car nose-up. | Safety | shop |
| Socket set 10 mm and 12 mm, 3/8 in drive, 6-point 10 mm for the under-tray and splash shields, 10/12 mm for thermostat housing bolts depending on engine. | Required | shop |
| Ratchet and extensions 3/8 in drive, 3 in and 6 in extensions plus swivel Reaches the housing bolts tucked behind the lower hose. | Required | shop |
| Trim clip / panel removal tool Plastic pry set Pops the plastic fir-tree clips holding the engine under-tray and splash shield. | Required | shop |
| Drain pan 6 qt / 6 L minimum, wide Catches coolant from the radiator drain and the lower hose. | Required | shop |
| Hose clamp pliers Spring-band clamp pliers, cable type preferred Releases the lower radiator hose clamp at the thermostat housing in tight quarters. | Required | shop |
| Flat screwdriver Medium, long shaft Opens the plastic radiator drain plug and breaks the hose loose from the housing neck. | Required | shop |
| Pick or hose removal tool 90-degree pick Frees a stuck hose from the housing without cutting it. | Recommended | shop |
| Gasket scraper Plastic or brass, non-marring Cleans the aluminum housing face without gouging it. | Recommended | shop |
| Torque wrench 1/4 or 3/8 in drive, 5-25 ft-lb range Small M6/M8 bolts into aluminum strip easily if guessed. | Required | shop |
| Funnel kit Spill-free funnel with Honda/universal radiator neck adapter Fills and burps the system without airlocks — essential on these engines. | Required | shop |
| Coolant tester or refractometer Confirms mix strength if you dilute concentrate or top up. | Recommended | shop |
| OBD-II scan tool Live-data capable, reads ECT Watch coolant temp and fan operation while burping; clears any P0128/P0217 codes. | Recommended | shop |
| Thermostat with gasket Honda 19301-5A2-A02 style assembly for 1.5T/2.0T; confirm by VIN — hybrid uses its own part The replacement unit; Honda sells it as a thermostat with integral rubber seal. | Parts | shop |
| Thermostat housing gasket / O-ring Included with OEM thermostat; buy separately for aftermarket Sealing the cover to the block; never reuse the old rubber. | Parts | shop |
| Honda Type 2 coolant Blue, pre-mixed, 2 gallons for a full flush; 1 gallon for drain-and-fill Honda-specific silicate-free formula; do not substitute green or universal orange. | Consumables | shop |
| Distilled water 1 gallon Rinse and top-up only; never tap water. | Consumables | shop |
| Nitrile gloves and eye protection Coolant is a skin and eye irritant and the system may still be hot. | Safety | shop |
| Insulated HV gloves Class 0, 1000 V — hybrid only Required precaution before touching anything near orange cabling on the hybrid. | Safety | shop |
| Shop towels and parts cleaner Brake or general purpose cleaner Cleans the sealing face and mops up spilled coolant. | Consumables | shop |
1.5T (L15BE) and 2.0T (K20C4) both use a block-mounted housing with two bolts, most commonly 10 mm heads on M6 fasteners; some 2.0T housings use 12 mm heads, so carry both. The hybrid's 2.0 Atkinson (LFA) uses the same tooling but a different thermostat part number and requires the high-voltage service disconnect procedure before you start. Under-tray fasteners are 10 mm on all trims, with more plastic clips on Sport and Touring aero trays.
| Thermostat housing / cover bolts (M6, 10 mm head) | 9.8 Nm (7.2 ft-lb) — verify in the service manual for your engine |
| Thermostat housing bolts if M8, 12 mm head | 22 Nm (16 ft-lb) — verify in the service manual |
| Radiator drain plug (plastic) | Hand-snug only, do not use a tool to tighten — verify in the service manual |
| Engine under-tray bolts (10 mm) | 9 Nm (7 ft-lb) — verify in the service manual |
| Hybrid high-voltage service plug cover bolts | verify in the service manual |
The 10 mm / 12 mm housing bolt sizes, 10 mm under-tray bolts and the lower-hose-side housing location are consistent across the 10th-gen Accord, but bolt head size can vary between the 1.5T, 2.0T and hybrid housings — check yours before buying, and confirm the thermostat part number by VIN as well as the torque figures in the factory service manual.
It is in a housing bolted to the lower front of the engine block, on the side where the lower radiator hose connects — not in the upper hose. You reach it from underneath after removing the plastic engine under-tray.
A radiator drain gives up roughly 3-4 quarts, so one gallon of pre-mixed Honda Type 2 blue coolant is enough for a drain-and-fill. Budget two gallons if you plan to flush the whole system.
Most 10th-gen Accords use two M6 bolts with 10 mm heads; some 2.0T housings use 12 mm heads. Have both sockets plus a 3 in and 6 in extension and torque to spec — they go into aluminum.
Yes — a stuck-open thermostat commonly triggers P0128 (coolant temp below thermostat regulating temperature), often with slow warm-up and weak heat. Confirm with live ECT data, since low coolant or a faulty sensor produce the same code.