Description
Factory Mercedes-Benz 300SE / 300SEL / 300SDL Workshop Manual (1986–1991)
This is the official factory-level service manual for the W126-chassis Mercedes-Benz 300SE, 300SEL, and 300SDL — covering every repair and maintenance procedure needed to keep these S-Class sedans running at their best across all US-market model years from 1986 through 1991.
Powertrain & Drive Coverage
| Component | Variants Covered |
|---|---|
| Petrol | M103 3.0L SOHC inline-six with Bosch fuel injection (300SE, 300SEL) |
| Diesel | OM603 3.0L turbocharged inline-six diesel (300SDL) |
| Transmissions | 4-speed automatic with torque converter |
| Drive | RWD |
| Model Years | 1986–1991 |
| Badge Twins | N/A |
Common 300SE / 300SEL / 300SDL Repairs Covered
| System | Procedures |
|---|---|
| M103 Engine — Oil Leaks | Camshaft cover gasket, front crankshaft seal, and timing chain cover reseal procedures |
| OM603 Diesel — Injection System | Injection pump timing, injector removal and testing, turbocharger inspection and replacement |
| Hydraulic Self-Leveling Suspension | Rear self-leveling strut replacement, hydraulic pump service, accumulator inspection |
| Climate Control — Vacuum System | Vacuum line routing, heater valve replacement, HVAC actuator diagnosis and repair |
Format & Delivery
PDF. Instant download; lifetime re-downloads.
Frequently Asked Questions
Why does my W126 300SE develop oil leaks around the engine?
The M103 3.0L inline-six is known for aging camshaft cover gaskets and front crankshaft seals that harden and weep over time. This manual includes full reseal procedures with torque specs for the camshaft cover, timing chain cover, and rear main seal, so you can address these leaks without guesswork.
What chassis platform do these models share?
All three variants — the 300SE, long-wheelbase 300SEL, and long-wheelbase diesel 300SDL — ride on Mercedes-Benz’s W126 S-Class platform. The 300SE uses a standard wheelbase while the 300SEL and 300SDL stretch the rear compartment for greater passenger room. This manual covers all W126 body configurations produced between 1986 and 1991.
Does this manual cover the OM603 diesel injection and turbocharger system?
Yes. The 300SDL’s OM603 turbodiesel is fully covered, including injection pump timing adjustments, individual injector testing and replacement, glow plug system diagnostics, and turbocharger removal, inspection, and installation. Fuel system bleeding procedures are also included.
What format is the manual?
The manual is delivered as a PDF file — downloadable immediately after purchase and compatible with any PDF reader on Windows, Mac, or mobile devices. You can search by keyword, zoom into wiring diagrams, and print any pages you need at the bench.
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