Nissan SD22, SD23, SD25, SD33 Service Manual – Factory Diesel Engine Specs

If you are working on a Nissan diesel from the SD series – SD22, SD23, SD25, or SD33 – and you are reaching for aftermarket data, stop. I have seen one too many backyard builds where the head gasket blew because someone used a torque value out of a third-party book. This is the genuine Nissan Service Manual for the SD22, SD23, SD25, and SD33 engines. 52 pages of factory procedure, no filler. You want the cylinder head bolt torque for the SD22? It is on the internal components diagram: 167–172 N·m (123–127 ft-lb) for SD22 and SD33, 51–71 N·m (38–41 ft-lb) for SD23 and SD25. That is the kind of detail you get when the manual was written by the engineers who designed the engine.

Engine Mechanical Section – What’s Inside

The manual is built around Section EM – Engine Mechanical. It covers everything from outer engine components (injection pump, oil cooler, alternator) to internal parts like the camshaft, crankshaft, valve mechanism, and piston assembly. The table of contents lists ENGINE DISASSEMBLY with precautions and step-by-step removal of the transmission, clutch, and starter. Then INSPECTION AND REPAIR: cylinder head and valve, camshaft and camshaft bushing, cylinder block, cylinder liner, piston and rings, connecting rod, crankshaft, bearings, pilot bushing, combustion chamber, flywheel, gear train, front case. Each section has the factory tolerance and wear limits. You don’t guess – you measure.

Does This Manual Cover the SD33 Diesel?

Yes. The cover specifically states SD22, SD23, SD25, and SD33. The torque table on the internal parts diagram shows two sets of values – one for SD22/SD33 and another for SD23/SD25. For example, the main bolt torque: SD22 and SD33 get 167–172 N·m, while SD23 and SD25 get 68–71 N·m. That is not a typo – those engines have different cylinder block castings and bolt grades. The manual also lists the crankshaft bearing clearances and the piston ring end gaps for each displacement. If you are rebuilding an SD33 from a forklift or a marine application, this is the reference you need.

52 Pages of Factory Diesel Specs

52 pages might not sound like a lot compared to modern full-vehicle manuals, but for a diesel engine only, it is dense. Every page is packed with exploded diagrams, torque callouts, and inspection limits. The SERVICE DATA AND SPECIFICATIONS section near the back gives you the compression pressures, valve timing marks, and fuel injection pump timing. There is even a SPECIAL SERVICE TOOLS list so you know exactly what puller or adapter you need before you start. I keep a copy laminated in the shop for the Nissan diesel truck that rolls in twice a year. Saves me from calling the dealership.

Check the Torque Values Before You Bolt Anything

The TIGHTENING TORQUE section lists every fastener on the engine – intake manifold (8–11 N·m, 5.8–8.0 ft-lb), exhaust manifold (15–18 N·m, 11–13 ft-lb), cylinder head bolts (the big ones above), oil pump, front cover, timer cover. These are not suggestions. If you over-torque a glow plug (4–8 N·m, 2.9–4.3 ft-lb) you crack the swirl chamber. The manual tells you that the glow plug must be replaced if removed, and the torque is specific. Follow it.

Cylinder Head Assembly: Factory Procedure

The manual walks you through assembling the cylinder head – valve lifter, push rod, rocker shaft assembly, camshaft, and the swirl chamber (combustion chamber). It shows the order of tightening and the angle if applicable. For the SD23 and SD25, the main bolt torque is 68–71 N·m, and for SD22/SD33 it is 167–172 N·m. Do not mix them up. Also note the gear train section – the manual marks gears with order numbers so you align the camshaft and injection pump timing correctly. Miss that by one tooth and the engine won’t start.

Source Authenticity – OEM vs Aftermarket

You are buying the original Nissan publication, not a scanned reprint from a third party that lost resolution on the torque tables. The manual is a direct PDF of the 2nd revision factory document. I have tested aftermarket manuals that claimed to cover the SD series – they skipped the SD33 entirely or used generic values. This one has the Nissan logo, part number, and the exact same diagrams I saw when I worked at a Nissan dealer in the 90s. If you are serious about keeping that diesel running, you use the factory data.

Need a related manual for other Nissan work? Check the Nissan SD22 SD23 SD25 SD33 Service Manual – Factory Diesel Engine Specs for your own reference, or the Nissan Xterra 2005 Service Manual – OEM Factory Spec if you are dealing with a gasoline VQ engine. For older work, the Nissan 60 1967 Service Manual – Original Factory Bulletin covers the vintage patrol engines. For general automotive industry context on OEM documentation standards, see Automotive Industry Overview and Automotive Industry Overview.

How many pages does this manual have?

52 pages.

Does it cover torque specs for all four engines separately?

Yes. The manual includes separate torque values for SD22 and SD33 (167–172 N·m main bolt) versus SD23 and SD25 (68–71 N·m main bolt). It also lists lower torque for intake, exhaust, oil pan, and other fasteners. The page 4 (engine components internal) shows the cylinder head torque range per engine. The service data section later gives the full tightening torque table for every bolt in the assembly. You will not find a single aftermarket manual that breaks it down this precisely because the factory had to account for different block castings and cylinder liner types across the four displacements. Use the correct column.

Download the Factory Manual and get the right data the first time. No guessing, no reprints – just the Nissan specification your engine deserves.