Toyota Diesel OEM 2L 2L-T 2L-TE 3L 5L Thermostat O-RING SEAL Hilux Surf Land Cruiser 4Runner 16341-35010

Product Overview

Genuine OEM Toyota upper thermostat housing O-ring seal 16341-55010, compatible with the Land Cruiser Bundera (LJ70, RJ70), Hilux Surf (LN130), 4Runner (LN130), and late-production Hilux (LN86, LN106, LN107, LN111, LN147, LN152, LN167, LN172) running the 2L-T, 2L-TE, and 3L diesel engines. This is the current part number for the seal that fits between the upper thermostat housing and the water inlet, and it is one of the most commonly needed cooling system parts on these diesel 4x4s because the housing has to come off any time the thermostat or housing itself is serviced. Toyota's parts catalog also lists this seal against 22R and 22R-E petrol Hilux and 4Runner variants that share the same housing design, so the same physical seal appears across both fuel types, even though this listing focuses on the diesel fitment. 

OEM Part Number(s):

• 16341-55010 (current)
• 16341-35010 (superseded / previous)
• 16341-05020 (superseded / previous)

 

Key Features & Benefits

• Perfect Fit: Engineered to Toyota's exact tolerances for the upper thermostat housing on 2L-T, 2L-TE, 3L, 5L diesel engines, eliminating the fit issues common with generic aftermarket O-rings
• Quality Assurance: Genuine Toyota O-ring seal material designed to hold its shape and sealing pressure through repeated heat cycles, unlike generic rubber that hardens and flattens with age
• Cooling System Integrity: Stops the slow coolant seep at the housing that leads to low coolant, air pockets, and overheating on a diesel engine that already runs a tighter cooling margin than its petrol counterpart
• Easy Installation: Beginner-friendly replacement that pairs naturally with a thermostat swap or upper housing service

 

Technical Specifications

Part Type: Upper thermostat housing O-ring seal
Material: Rubber O-ring seal
Engine Compatibility: 2L-T (2.4L turbo diesel), 2L-TE (2.4L turbo diesel), 3L (2.8L diesel, late production), 3L/5L/5L-E (2.8L/3.0L diesel)
Companion Thermostat: 16340-54040 (82°C/180°F opening temperature) for 2L-T, 2L-TE, 3L, and 3L/5L/5L-E applications
Supersession: Current number 16341-55010 replaces 16341-35010 and 16341-05020; the same physical part appears under all three numbers across parts sites and forum threads

Fitment

Year	Model	Engine
11/1984-7/1992	Land Cruiser Bundera (LJ70, RJ70)	2L-T (2.4L Turbo Diesel)
4/1989-7/1993	Hilux Surf (LN130)	2L-TE (2.4L Turbo Diesel)
5/1995-1/2005	Hilux (LN86, LN106, LN107, LN111, LN147, LN152, LN167, LN172)	3L (2.8L Diesel, late production)
5/1995-10/1995	4Runner (LN130)	3L / 5L / 5L-E (2.8L / 3.0L Diesel)

Important: Verify part compatibility using your vehicle's VIN or engine code before purchase. This is the current seal design; on late-production 3L engines built before 5/1995, Toyota used a flat gasket (part 16341-54040) at this same location instead of this O-ring, so confirm your production date if you have an early 3L before ordering. This part is not the same as the U.S.-market Toyota Pickup diesel gasket sold under 16341-35010 for the 1984-1986 2L and 2L-T Pickup — that regional catalog listing has not been confirmed to follow this same supersession chain, so U.S. Pickup diesel owners should verify separately rather than assume this current number applies. This listing is scoped to the diesel-engine applications above; the same seal is also used on 22R/22R-E petrol Hilux and 4Runner variants if you need it for that application instead.

Installation & Maintenance

Installation Difficulty: Beginner
Estimated Install Time: 0.5-1 hour
Tools Required: Basic socket set, gasket scraper or pick, torque wrench, coolant drain pan
Professional Installation: Not required for most DIY mechanics, though flagged as intermediate if the housing bolts are corroded or the mating surfaces need cleanup

Maintenance Tips:

• Always replace this O-ring when the upper thermostat housing is removed, even if the old seal looks intact
• Clean the O-ring groove completely of old seal material and debris before seating the new O-ring
• Seat the O-ring fully and evenly in its groove before drawing the housing down, since a pinched seal is a common cause of a leak right after reassembly
• Torque housing bolts evenly in a criss-cross pattern to Toyota specification to avoid warping the housing or crushing the seal unevenly
• Bleed the cooling system fully after reassembly and recheck coolant level once the engine has cycled through a full heat cycle

 

Frequently Asked Questions

Q: What's included in the package?
A: This listing includes one genuine Toyota OEM upper thermostat housing O-ring seal, part number 16341-55010. The thermostat, housing bolts, and coolant are sold separately.

Q: How difficult is installation?
A: Replacing this O-ring is a beginner-level job that typically takes under an hour when done alongside a thermostat replacement. It requires draining a small amount of coolant, removing the upper housing bolts, cleaning the O-ring groove, and reinstalling with the new seal and correct torque.

Q: Does this seal fit my early 3L engine?
A: It depends on your production date. Late-production 3L engines (from roughly May 1995) use this O-ring seal, but earlier 3L engines used a flat gasket (Toyota part 16341-54040) at this same location. Check your production date or compare the old part before ordering, since installing the wrong style will not seal correctly.

Q: Can I reuse my old O-ring instead of buying a new one?
A: Reusing this O-ring is not recommended. Rubber seals compress, flatten, and lose their sealing memory over time and heat cycles, which is why most coolant weeps at this joint traces back to a reused O-ring rather than a defective new one.

Related Toyota Parts You May Need

• Toyota Diesel OEM 2L, 2L-T, 2L-TE, 3L, 5L 82°C Thermostat 16340-54040 - The companion thermostat for this housing, worth replacing at the same time since both parts wear together
• Radiator Hose (upper and lower) - Often hardened or cracked by the same age and heat cycles that degrade the housing seal
• Coolant Reservoir Cap - A weak cap seal masquerades as a housing leak by letting the system run at reduced pressure
• Water Pump Assembly - Shares the same coolant circuit and service interval, and is commonly inspected during thermostat housing work
• Genuine Toyota Coolant (Long Life) - Required after any cooling system service to maintain proper corrosion protection
• Housing Bolts / Studs - Worth replacing preemptively on high-mileage trucks where the originals show corrosion, since a snapped bolt turns a simple seal job into an extraction job

 

Common Symptoms of Thermostat Housing Seal Failure

• Coolant seepage or a slow drip visible around the upper thermostat housing bolts
• A sweet smell of coolant in the engine bay after driving
• Low coolant level in the reservoir that keeps returning after topping off
• White or crusty mineral deposits forming on and around the housing surface
• Engine temperature gauge creeping higher than normal, especially under the added load a diesel carries when towing or off-road
• Coolant loss that appears immediately after a thermostat job, before the engine has even run