Need the factory rebuild procedures for your David Brown 990 or 1200 Selectamatic? This 48-page repair manual (OEM #9-37121) covers the 1200 Selectamatic Livedrive and Non-Livedrive, 990 Selectamatic Livedrive and Non-Livedrive, and 990 Non-Livedrive Twin-plate clutch tractors. Inside: valve clearance adjustments and cylinder head removal, a complete decarbonising sequence, piston and connecting rod service, camshaft replacement, fuel injection pump timing and controls, and water pump rebuild from bearing to impeller. You also get exploded views of every engine component in position, system diagrams for timing gear assembly, and injector nozzle testing procedures from atomisation checks through needle valve cleaning. Cylinder head nuts torque to 90 lb ft, engine oil capacity is 7.4 litres, and the cooling system takes 13.6 litres. Chasing an injection fault without the factory numbers is a money pit. Bookmarked by section so you jump straight to injection pump timing or camshaft clearances. Download it, open on your tablet, and start wrenching.
What's Inside This David Brown 990, 1200 Selectamatic Repair Manual
| System | Pages | Key Topics |
|---|---|---|
| Maintenance | 5-6 | Engine Oil, Air Cleaner, Cooling System, Sediment Bowl, Fuel Filter, Fan Belt |
| Adjusting Valve Clearance | 8 | Valve Clearance, Rocker Arm, Valve Stem, Adjusting Screw, Locknut |
| Removing and Replacing Cylinder Head | 8 | Cooling Water, Air Inlet Pipe, Manifolds, Valve Rocker Cover, Rocker Shaft, Push Rods, Cylinder Head Nuts, Gasket |
| Decarbonising Cylinder Head | 9-13 | Cylinder Head, Valves, Injectors, Valve Seats, Valve Guides, Piston Rings |
| Pistons and Connecting Rods | 14 | Pistons, Connecting Rods, Piston Rings, Gudgeon Pins, Connecting Rod Alignment |
| Camshaft | 15-16 | Locating-Plate, Camshaft Gear, Valve Rockers, Tappets, Camshaft Bearings |
| Injectors | 17-19 | Injector Removal, Nozzle Testing, Atomisation Test, Nozzle Cleaning, Needle Valve, Nozzle Body |
| Fuel Feed Pump | 20 | Fuel Pipe Union, Push-Rod, Diaphragm, Pull-Rod, Priming Lever |
| Fuel Filter | 20 | First Filter Element, Second Filter Element, Bowl, Retaining Bolt, Sealing Ring |
| Venting Fuel System | 21-22 | Fuel-Feed-Pump Outlet Union, Hand Primer, Filter Vent Plug, Injection Pump Vent Plug, Injector Unions |
| Fuel Injection Pump | 23-25 | Injection Pump Removal, Pump Replacement, Pump Timing, Injection Pump Controls, Injection Pump Fuel Setting, Checking Engine Spill Timing |
| Fuel Tank | 26-27 | Fuel Tank Removal, Instrument Panel, Engine-Speed-Indicator Drive Cable, Fuel Outlet Pipe, Fuel Leak-Off Pipes |
| Lubricating Oil Filter | 28 | Filter Bowl, Filter Element, By-Pass Valve, Sealing Ring, Securing Bolt |
| Lubricating Oil Pump | 28-30 | Pump Removal, Oil Pump Screen, Pump Dismantling, Pump Replacement, Pump Bracket Bush, Relief Valve |
| Air Cleaner | 31 | Cleaner Bowl, Wire Mesh Element, Oil Bath, Pre-Cleaner, Rubber Ring, Inlet Pipe |
| Timing Cover | 31 | Timing Cover Removal, Timing Cover Refitting, Oil Seal Replacement, Crankshaft Pulley |
| Timing Gears | 32-34 | Camshaft Gear, Intermediate Gear, Injection Pump Drive Gear, Crankshaft Gear, Assembling Timing Gears |
| Water Pump | 35-39 | Water Pump Gland, Water Pump Bearing, Pulley, Impeller, By-Pass Seal |
| Dimensional Data | 40-43 | Torque Figures, Capacities, Wear Limits, Valve Clearance, Crankshaft, Piston Dimensions |
| Summary of Design Changes | 44-48 | Rear Main Bearing Oil Retainer, High-Lift Camshaft, Valves, Pistons, Injection Pump Drive Gear, Timing Cover, Engine Oil Filler, Radiator Core |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| All Models | ||
| Clutch housing to main frame bolts torque | 75 lb ft (10.5 kg metres) | p. 40 |
| Engine lubricating oil filter replacement interval | Every 250 Hours | p. 5 |
| Engine Oil Capacity | 7.4 litres | p. 40 |
| Cooling System Capacity | 13.6 litres | p. 40 |
| Cylinder Head Nuts and Bolts Torque | 90 lb ft | p. 40 |
| Main Bearing Cap Bolts Torque | 160 lb ft | p. 40 |
| Inlet Valve Clearance (set cold) | 0.010 in | p. 41 |
| Exhaust Valve Clearance with stem end caps (set cold) | 0.007 in | p. 41 |
| Injector Setting Pressure | 175 atmospheres | p. 43 |
| Oil Filter Bowl Bolt Torque | 10 lb ft | p. 40 |
| 1200 (4/55) | ||
| Spill Timing (static) for 1200 (4/55) | 25° before top dead centre | p. 43 |
| 990 (4/49) | ||
| Spill Timing (static) for 990 (4/49) | 17° before top dead centre | p. 43 |
David Brown 990, 1200 Selectamatic Common Problems This Manual Covers
David Brown 990 twin-plate clutch fails to disengage, gears grind on every shift
Remove the hydraulic clutch release cover. If the screws are seized, tap the housing free with a mallet rather than forcing the screws. Clean or replace the bypass valve if it sticks in the open or closed position. On reassembly, torque clutch housing to main frame bolts to 75 lb ft (10.5 kg metres).
Manual Section: Engine Removal and ReplacementCoolant leaking from lower rear of engine block, head gasket and water pump both checked out p. 5
Inspect the rear of the block for a failed core plug (freeze plug). These cast-iron blocks regularly lose their core plugs to rust and thermal fatigue after years of service. Drive out the failed plug from inside the block, clean the bore, and press in a replacement. Drain and refill the cooling system to its full 13.6 litre (3 gal) capacity.
Manual Section: MaintenanceEngine won't fire or takes excessive cranking to start, especially when fuel system disturbed p. 21
Vent air from the fuel system before anything else. Work from the filter vent plug to the injection pump vent plug using the hand primer, as shown on page 21, until fuel flows bubble-free. Test injectors: opening pressure must be 175 atmospheres (180 kg/cm²). If compression feels soft, check inlet valve clearance (0.010 in / 0.25 mm cold).
Manual Section: Venting Fuel SystemOil pressure warning light on at idle, flickers at speed, engine not knocking yet p. 28
Remove and clean the oil pump screen (page 28) before condemning the pump. The wire mesh inlet screen clogs with sludge on high-hour engines and kills oil pressure without any pump wear. Verify oil level (total capacity 7.4 litres) and replace the filter element at the 250-hour mark. Measure pump rotor clearances if cleaning the screen does not restore pressure.
Manual Section: Lubricating Oil PumpValve train rattling loudly after top-end work, rough idle, rocker cover just refitted p. 8
Set valve clearances with the engine stone cold. Inlet valves need 0.010 in (0.25 mm); exhaust valves fitted with stem end caps need 0.007 in (0.18 mm). Work through each cylinder in the firing order sequence on page 8, snugging the locknut firmly after each adjustment. A single over-tight exhaust rocker causes both rattling and partial valve burn.
Manual Section: Adjusting Valve ClearanceRough idle and misfire at one cylinder, white smoke that does not clear at temperature p. 17
Remove the injector from the suspect cylinder and test on a bench tester. The nozzle must open at exactly 175 atmospheres (180 kg/cm²) with complete atomisation and a dry seat below that pressure. Follow the nozzle inspection and cleaning procedure on page 17. Replace the nozzle assembly if it dribbles, streams, or fails the back-leakage test.
Manual Section: InjectorsFrequently Asked Questions
What are the torque specs for the clutch housing bolts on 990 Selectamatic?
For 990 Selectamatic tractors, the clutch housing to main frame bolts should be torqued to 75 lb ft (10.5 kg metres). This specification is found in the Dimensional Data section of the manual.
What are the replacement specifications for Freeze plug (rear engine block core plug)?
The cylinder block core plugs were changed from part number 17192 to cup type plugs part number 623797. Due to changes in plug aperture machining, the old and new plugs are not interchangeable for replacement.
What is the engine oil capacity and valve clearance specification for the David Brown 990 and 1200 Selectamatic tractor?
The engine holds 7.4 litres of oil (page 40). Set inlet valve clearance to 0.010 in cold and exhaust valve clearance (with stem end caps) to 0.007 in cold, as specified on page 41. Always check valve clearance with the engine cold before initial startup or after valve train service.
What are the cooling system capacity and cylinder head torque specs for the David Brown 990 and 1200 Selectamatic?
The cooling system holds 13.6 litres (page 40). Torque cylinder head nuts and bolts to 90 lb ft and main bearing cap bolts to 160 lb ft, as specified on page 40 of the repair manual.
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