Toyota 12H-T

Toyota 12H-TThe Toyota 12H-T is a 4.0 L (3,980 cc, 242.9 cu·in) six cylinders, four-stroke cycle water-cooled turbocharged internal combustion diesel engine, from the Toyota H-family, manufactured by the Toyota Motor Corporation.

The 12H-T diesel engine has a cast-iron cylinder block with 91.0 mm (3.58 in) cylinder bores and a 102.0 mm (4.02 in) piston stroke. Compression ratio rating is 18.6:1. The motor has a cast iron cylinder head with the overhead valves (2 per cylinder, 12 in total), direct injection fuel system and turbocharger.

The Toyota 12H-T engine produced 136 PS (100 kW; 134 HP) at 3,500 rpm of maximum horsepower and 315 N·m (32.1 kg·m, 232.2 ft·lb) at 1,800 rpm of peak torque.

The breakdown of the engine code is as follows:

  • 1 – Direct injection
  • 2 – 2nd generation engine
  • H – Engine family
  • T – Turbocharger

General information

Engine Specifications
Engine code12H-T
LayoutStraight-6, vertical
Fuel typeDiesel
Displacement4.0L, 3,980 cc (242.9 cu in)
Injection pumpMechanical
Power adderTurbocharger
Horsepower net 136 PS (100 kW; 134 HP) at 3,500 rpm
Torque output 315 N·m (32.1 kg·m, 232.2 ft·lb) at 1,800 rpm
Firing order1-4-2-6-3-5
Dimensions (L x H x W):

Cylinder block

The cylinder block is made of cast iron. The crankshaft is supported by 7 bearings. The crankshaft bearings are made of aluminum alloy. Pistons are made of highly temperature-resistant aluminum alloy.

The cylinder bore is 91.0 mm (3.58 in), piston stroke is 102.0 mm (4.02 in) and compression ratio rating is 18.6:1.

Cylinder block
Cylinder block alloyCast iron
Compression ratio:18.6:1
Cylinder bore:91.0 mm (3.58 in))
Piston stroke:102.0 mm (4.02 in)
Number of piston rings (compression / oil):2 / 1
Number of main bearings:7
Cylinder bore inner diameter:91.000-91.030 mm (3.5827-3.5839 in)
Piston skirt diameter90.940-90.970 mm (3.5803-3.5815 in)
Piston ring groove:First0.139-0.204 mm (0.0055-0.008 in)
Second0.060-0.100 mm (0.0024-0.0039 in)
Oil0.020-0.060 mm (0.0008-0.0024 in)
Piston ring end gap:First0.200-0.470 mm (0.0079-0.0185 in)
Second0.200-0.440 mm (0.0079-0.0173 in)
Oil0.150-0.490 mm (0.0059-0.0193 in)
Piston pin outer diameter32.000-32.012 mm (1.2598-1.2603 in)
Connecting rod small end diameter (standard):32.008-32.020 mm (1.2602-1.2606 in)
Crankshaft main journal diameter:69.980-70.000 mm (2.7551-2.7559 in)
Crankpin diameter:54.980-55.000 mm (2.1646-2.1654 in)
Crankshaft center distance:51.0 mm (2.01 in)

Main bearing cap tightening procedure and torque specs:

  • 136 Nm; 13.9 kg·m; 100 ft·lb

After securing bearing cap bolts, make sure crankshaft turns smoothly by hand.

Connecting rod bearing nut

  • 88 Nm; 9.0 kg·m; 65 ft·lb

Crankshaft pulley bolt

  • 441 Nm; 45.0 kg·m; 325 ft·lb

Drive plate (A/T) fixing bolts

  • 98 Nm; 10.0 kg·m; 72 ft·lb

Flywheel (M/T) fixing bolts

  • 118 Nm; 12.0 kg·m; 87 ft·lb

Cylinder head

Cylinder head
Cylinder head alloyCast iron
Valve Arrangement:OHV
Valves:12 (2 valves per cylinder)
Intake valves diameter:
Exhaust valves diameter:
Intake valves length:120.7 mm (4.752 in)
Exhaust valves length:120.6 mm (4.748 in)
Intake valve stem diameter:8.973-8.989 mm (0.3533-0.3539 in)
Exhaust valves stem diameter:8.954-8.970 mm (0.3525-0.3531 in)
Valve spring free length: Inner: 44.3 mm (1.7441 in)
Outer: 48.1 mm (1.8937 in)
Camshaft journal diameter: 1: 51.151-51.170 mm (2.0138-2.0146 in)
2: 50.951-50.970 mm (2.0059-2.0067 in)
3: 50.751-50.770 mm (1.9981-1.9988 in)
4: 50.551-50.570 mm (1.9902-1.9901 in)
Camshaft lobe height (intake):41.400 mm (1.6299 in)
Camshaft lobe height (exhaust):41.800 mm (1.6457 in)

Head tightening procedure and torque specs:

  • 113 Nm; 11.5 kg·m; 83 ft·lb

Maintenance data

Valve clearance (Hot)
Intake valve0.20 mm (0.0079 in)
Exhaust valve0.36 mm (0.0142 in)
Compression pressure
Standard30.0 kg/m2 (2,940 kPa, 427 psi)
Minimun20.0 kg/m2 (1,960 kPa, 284 psi)
Compression differential limit between cylinders2.0 kg/m2 (196 kPa, 28 psi)
Oil system
Recommended engine oil10W-30 or 5W-30 (“CC”, “CD”)
Engine oil capacity Dry fill: 10.3 L (10.9 US qt, 9.1 Imp. qt)
With oil filter change: 9.7 L (10.3 US qt, 8.5 Imp. qt)
Without oil filter change: 8.1 L (8.6 US qt, 7.1 Imp. qt)
Oil pressure: At idle: 0.3 kg/m2 (29 kPa, 4.3 psi) or more
At 3,00 rpm: 2.5-6.0 kg/m2 (245-588 kPa, 36-85 psi)
Fuel system
Injection nozzle opening pressure: Reused: 180-210 kg/m2 (17,650-20,600 kPa, 2,560-2,990 psi)
New: 200-210 kg/m2 (19,610-20,600 kPa, 2,845-2,990 psi)
Idling M/T: 650 ± 50 rpm
A/T: 700 ± 50 rpm
Maximum speed:4,100-4,170 rpm
Turbocharging pressure0.39-0.53 kg/m2 (38-52 kPa, 5.5-7.3 psi)

Vehicle applications

ModelYears Produced
Toyota Land Cruiser (HJ61)
Toyota Coaster (HB20, 30)
Author: Sergei Wers
About: Co-founder and CEO of a multi-brand auto repair shop (engine repair, chassis repair, body repair and painting) for over 15 years. I have been developing internet sites with technical specifications for more than seven years.

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  1. was the engine introduced in 1985? Looking at a 1986 hj61, just wondering if any changes were made to the engine in later 12ht fitted cars?

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