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Autopapyrus · Toyota Dyna S05C (2003)
https://autopapyrus.com/guides/toyota/dyna/engine-overhaul/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.

Toyota Dyna S05C (2003): Engine Overhaul

The S05C is an inline 4-cylinder Hino diesel of about 5.3 L (5.6 qt) displacement, mounted longitudinally under the cab in the Dyna U300/U400. The overhaul includes removing the engine, complete disassembly, measuring, machining the block, cylinder head and crankshaft, reassembly with replacement of all wear parts, and break-in. Take the specific clearances and tightening torques for this engine strictly from the manufacturer's service manual. Below I give the work sequence and general principles.

Difficulty: Hard Time: 4-7 working days (removal, inspection, boring and grinding at a machine shop, assembly) Steps: 15 Tools: Engine hoist or overhead crane (approx. 450-500 kg for the engine with accessories), torque wrench up to 300 N·m (221 lb-ft), bore gauge and micrometers, feeler gauges, dial indicator, Plastigage, valve spring compressor, cylinder liner puller if needed, seal driver, piston ring compressor, graduated cylinder or burette for injector testing, multimeter

Part

  • 🔩 S05C overhaul kit: pistons with rings and wrist pins, main and connecting rod bearings, crankshaft thrust washers, complete gasket and seal set, cylinder head gasket, oil pump if worn, valve stem seals, valve guides and valves as determined by inspection, oil filter, fuel filter, coolant. The injection pump and injectors are usually bench-tested (Denso pump, Denso injectors; the S05C-TB is turbocharged). Component cost depends on the manufacturer and the scope of the repair. Machine shop work (boring, honing, crankshaft journal grinding, pressure testing and resurfacing of the cylinder head) should be budgeted separately

Step by step

15 steps
  1. Determine that a full overhaul is really needed. Signs: low oil pressure on a warm engine, increased oil consumption, smoke, loss of compression (difference between cylinders greater than 10-15%), bearing knock, blow-by. First rule out simpler causes: injectors, injection pump, turbocharger, worn valve stem seals.
  2. Preparation. Disconnect the battery, drain the oil and coolant, take photos, and label the hoses, connectors and linkages. On this Dyna the work is done with the cab tilted. Secure the cab on its factory support, or remove it if the engine is being lifted out upward.
  3. Remove the hood and grille, the radiator with fan and shroud, the intercooler and pipes, and the exhaust pipe from the turbocharger. Then remove the fuel and vacuum lines, the accelerator linkage, the starter and the alternator. If the engine has an EGR system or sensors, disconnect the wiring harnesses.
  4. Separate the transmission from the engine and support it with a jack. Remove the clutch cover and disc, and mark the flywheel. Remove the engine mounts and carefully lift the engine out with the hoist. Secure it on an engine stand for disassembly.
  5. Disassembly. Remove the turbocharger, manifolds, injection pump, injectors, valve cover, rocker arms and pushrods, and the cylinder head (tighten and loosen the bolts in a spiral pattern, from the outside to the center, following the sequence). Remove the oil pan, oil pickup, oil pump and drive gears. Mark the connecting rod caps and bearings by cylinder, then remove the pistons. Take out the crankshaft and camshaft. Lay out all parts in order.
  6. Inspection. Measure the cylinders with a bore gauge in two planes and at three levels (taper and out-of-round). Check the crankshaft journals, and the block and cylinder head surfaces with a straightedge and feeler gauge. Inspect the liners (if they are replaceable wet liners, check the fit and protrusion), and check the valves, guides and seats, the camshaft, lifters and rocker arms. Check the block and cylinder head for cracks by pressure testing. Wear limits are per the manufacturer's service manual.
  7. Machining. Bore and hone the block for oversize pistons (or replace the liners), grind the crankshaft for undersize bearings, resurface and pressure test the cylinder head, lap or replace the valves and seats, and replace the guides. Be sure to order the bearing and piston sets for the chosen oversize/undersize in advance.
  8. Preparation for assembly. Wash the block and cylinder head passages, clean the oil galleries with brushes, remove the plugs and install new ones. Lubricate all moving surfaces with engine oil or assembly lube. Use new gaskets, seals and locking elements for assembly.
  9. Bottom end assembly. Install the bearing shells in the block saddles, lay in the crankshaft, and check the oil clearance with Plastigage and the end play. Install the main bearing caps with a torque wrench (torque per the service manual, tightened in several passes). Install the pistons with rings (stagger the ring gaps about 120 degrees apart, with the mark on the piston crown facing the front of the engine), install the connecting rod caps, and check that the shaft turns freely after each pair.
  10. Install the oil pump, oil pickup, timing drive (drive gears aligned to the marks), and the oil pan with sealant. Measure the piston protrusion above the block surface: it determines the choice of head gasket thickness.
  11. Install the cylinder head with a new gasket of the correct thickness and tighten the bolts in sequence, in several passes. For bolts that use angle tightening or may be reused, check the service manual, as they are often replaced with new ones. Install the pushrods and rocker arms, and adjust the valve lash per the service manual on a cold engine.
  12. Install the valve cover, manifolds, turbocharger (fill it with oil and prime it before starting), injection pump and injectors. Bench testing and calibration are best for the injection pump and injectors, and set the injection timing using the marks.
  13. Reinstall the engine, connect the transmission, clutch, mounts, hoses, radiator and all the ancillaries. Fill with fresh engine oil of the required grade and quantity (per the service manual for the S05C) and coolant, and install new filters.
  14. First start. Prime the fuel system, and crank the engine with the starter with the fuel shutoff disconnected until oil pressure shows on the gauge. Then start the engine and hold 1000-1500 rpm for 10-15 minutes, checking for leaks, oil pressure and temperature. Bleed the air from the cooling system.
  15. Break-in. For the first 1000-1500 km, avoid full load, prolonged running at maximum rpm, and heavy loads. Change the oil and filter after the first 500-1000 km, then per the maintenance schedule. Check the cylinder head bolt torque and valve lash if the service manual requires it.

Common mistakes and warnings

  • This is a difficult job that requires precise measurements, machine shop work and bench testing of the fuel injection equipment. If you do not have experience overhauling diesel engines and the necessary equipment, leave the boring, grinding and injection pump calibration to a specialized shop. The engine is heavy, so work only with a sound hoist and secure the cab and engine firmly. Do not reuse old cylinder head or connecting rod bolts if the service manual requires replacing them, and do not try to set clearances or tightening torques by eye.
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