The 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 code | 12H-T |
Layout | Straight-6, vertical |
Fuel type | Diesel |
Production | – |
Displacement | 4.0L, 3,980 cc (242.9 cu in) |
Injection pump | Mechanical |
Power adder | Turbocharger |
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 order | 1-4-2-6-3-5 |
Dimensions (L x H x W): | – |
Weight |
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 alloy | Cast 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 diameter | 90.940-90.970 mm (3.5803-3.5815 in) | |
Piston ring groove: | First | 0.139-0.204 mm (0.0055-0.008 in) |
Second | 0.060-0.100 mm (0.0024-0.0039 in) | |
Oil | 0.020-0.060 mm (0.0008-0.0024 in) | |
Piston ring end gap: | First | 0.200-0.470 mm (0.0079-0.0185 in) |
Second | 0.200-0.440 mm (0.0079-0.0173 in) | |
Oil | 0.150-0.490 mm (0.0059-0.0193 in) | |
Piston pin outer diameter | 32.000-32.012 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 alloy | Cast 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 valve | 0.20 mm (0.0079 in) |
Exhaust valve | 0.36 mm (0.0142 in) |
Compression pressure | |
Standard | 30.0 kg/m2 (2,940 kPa, 427 psi) |
Minimun | 20.0 kg/m2 (1,960 kPa, 284 psi) |
Compression differential limit between cylinders | 2.0 kg/m2 (196 kPa, 28 psi) |
Oil system | |
Recommended engine oil | 10W-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 |
Turbocharger | |
Turbocharging pressure | 0.39-0.53 kg/m2 (38-52 kPa, 5.5-7.3 psi) |
Vehicle applications
Model | Years Produced |
Toyota Land Cruiser (HJ61) | – |
Toyota Coaster (HB20, 30) | – |
We try to use verified sources and official documentation, however, differences between sources or errors in entering information may occur. We do not provide advice on technical issues related to the engines operation or repair. We do not recommend using provided information for engines repairing engines or spare parts ordering, use only official service manuals and spare-parts catalogs.
Does the 12HT engine has a timing belt, timing chain or timing gears????
Timing gears
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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