Description

Mitsubishi 4G5 1990 Workshop Manual – Factory Documentation for the 4G5 Engine

If you’ve ever had a job go sideways because a torque spec was wrong, you know the feeling. A head gasket leak you didn’t catch because the manual you were using had generic values. That’s not happening with this 67-page factory Mitsubishi 4G5 1990 Workshop Manual. I’ve been wrenching for 28 years, and aftermarket copies lose details—like the exact order for rocker arm bolt tightening or the specific sealant for the oil pan. This is the OEM book straight from Mitsubishi Motors Corporation, October 1990 (Pub. No. PWEE9055). You get the real thing, not a third-party reinterpretation.

Engine 4G5 Series: General Specifications and Service Limits

The manual opens with General Information including General Specifications, Service Specifications, and Torque Specifications—all from the factory. Need the camshaft journal clearance? It’s in the service spec table. Cylinder bore wear limit? Listed. These numbers come from Mitsubishi’s engineering department, not some guy in a warehouse guessing. The Sealant section tells you exactly what compound to use on the rocker cover and oil pan. Skip that, and you’ll be wiping up oil next week.

Torque Specs: Why Aftermarket Copies Get It Wrong

Page 1 (the Torque Specifications section) lists every critical fastener: cylinder head bolts, main bearing cap bolts, connecting rod nuts. I’ve seen aftermarket manuals transpose ft.lbs. for Nm, or leave out the angle-tightening sequence for the head. This Mitsubishi manual gives you both Nm and ft.lbs. and includes the Sequence of removal versus installation. For the cylinder head, you need the order—loosen from outside in, tighten from center out. That’s on page 2 of the Cylinder Head and Valves chapter. If you ignore it, warped head.

Cylinder Head and Valves: Removal Steps You Can Trust

The Cylinder Head and Valves section (Group 11A) walks through removal in numbered steps—from cylinder head bolt to the valve guides. Non-reusable parts are marked clearly: head gasket, valve seals, retainer locks. The Service Points of Removal covers the jet valve assembly (engines with jet valves) and how to hold the special tool when loosening it. This is the kind of detail you won’t find in a generic manual. Also covered: Jet Valve Assembly (Engine with Jet Valves) and Timing Chain removal.

Rocker Arms and Camshaft: Inspection and Adjustment

Under Rocker Arms and Camshaft, the manual shows the disassembly sequence for the rocker shafts and camshaft. Valve clearance adjustment specs are included—both intake and exhaust. You get the factory procedure for checking camshaft lobe height and rocker arm oil clearance. No guessing whether that ticking noise is a lifter or a worn cam—the spec tells you. And because this is OEM, you know the values haven’t been altered for a “universal” fit.

Timing Chain, Oil Pump, and Silent Shaft Service

Two versions of the 4G5 came with or without a silent shaft. The manual covers both: Oil Filter, Oil Pump and Silent Shaft (Engine with Silent Shaft) and Oil Filter and Oil Pump (Engine without Silent Shaft). Timing chain tensioner adjustment, oil pump gear backlash, silent shaft alignment—all factory procedure. If you’re rebuilding a 4G5, you need this section. It also includes Piston and Connecting Rod and Crankshaft, Flywheel and Drive Plate removal.

Who Needs This Manual?

Home garage enthusiasts pulling a 4G5 from a Mighty Max or a Montero. DIYers doing a top-end rebuild. Anybody tired of chasing wrong specs on forums. This is a 67-page workshop manual—concise enough to find what you need fast, dense enough to include every torque value and clearance. If you’re replacing a cylinder head, swapping camshafts, or resealing the oil pan, this book saves you a call to the dealer.

Source Authenticity: OEM vs. Aftermarket

I’ve told every junior tech: never trust an aftermarket manual without cross-checking. The Mitsubishi 4G5 1990 Workshop Manual is an original factory document, not a reprint or a scan of a scan. The Filing Instruction on page 1 tells you how to insert revised pages—that’s how you know it’s the real thing. No third-party editing. No “extracted” diagrams that lost resolution. What you see is what Mitsubishi issued to their dealerships in 1990.

FAQ

Does this manual cover the silent shaft versions?

Yes. It has a separate section titled Oil Filter, Oil Pump and Silent Shaft (Engine with Silent Shaft).

I see torque specs listed—are they in imperial or metric?

Both. The manual gives Nm and ft.lbs. for every fastener, including cylinder head bolts, main bearing caps, and connecting rod nuts. It also includes the tightening sequence for the camshaft sprocket bolt. Page 1 of the torque specs shows all values. Don’t mix them up—use the ft.lbs. column if your torque wrench is calibrated in imperial. The factory procedure for the cylinder head requires an angle gauge after the initial torque, and that angle is specified in degrees. If you skip that step, you’ll lose clamping force. I’ve seen it happen. Also, note that some bolts—like the rocker arm shaft bolts—have a two-step torque: tighten to 14 ft.lbs., then another 90 degrees. That’s in the Rocker Arms and Rocker Shafts section. If you’re using an aftermarket manual that says “tighten to spec” without the angle, you’re asking for a valve train noise later. This OEM manual gives you the full procedure, including the special tool required to hold the jet valve during removal. And if you’re working on a 4G5 with jet valves, pay attention to the Jet Valve Assembly chapter—those things are easy to damage if you don’t follow the sequence.

Related manuals you might need: Mitsubishi R4AW2-1, R4AW2-3, R4AW2-7 1996 Workshop Manual for the transmission, Mitsubishi Engine 4D68 (E-W) Workshop Manual for a different diesel engine, and Mitsubishi Front Wheel Drive Automatic Transmission Repair Manual for transaxle work. For general industry background, see the Automotive Industry Overview and Manual Transmission articles. Access the Factory Manual and get the specs you can bet your toolbox on.