FAQs

Not all David Brown front loaders are compatible with every tractor model. Each loader is identified by a combination of letters and numbers found on an identification plate, typically located on the left underside of the loader frame.

For example: LF7

• L = Loader

• F = Front

• 7 = Designed for 770 & 780 tractors

Other common designations include:

• LF8 – for 880 tractors

• LF9 – for 990, 995, 996 tractors

• LF12 – for the 1200–1412 range

Loader Types

• LF loaders: Standard duty, single-acting rams

• LH loaders: Heavy duty, single-acting rams

• LS (Super Loaders): Double-acting rams

With the introduction of the 90 Series tractors, early models could still accept some LF loaders. However, these were soon replaced by the more robust H-type loaders:

• FD90 – Standard duty

• GD90 – General duty

• HD90 – Heavy duty

These were fixed-frame loaders. Later, QD (Quick Detach) loaders were introduced, featuring a detachable design. When Case IH took over and introduced red livery, these loaders were rebranded as:

• L1000, L1100, L1200, L1500 – where the number refers to the lifting capacity in kilograms

Hydraulics & Controls

• Early loaders used a single crowd ram; later QD and HD loaders had twin rams.

• QD loaders introduced improved hydraulic connections with a block of quick-release couplings integrated into the loader bracket. Operation was cable-controlled via the cab-mounted spool valve system.

• Earlier loaders connected to the tractor’s hydraulic system via a 3-way valve, using the standard hydraulic lever latched in the "select" position.

Due to HSE regulations, exposed oil pipes within the cab became prohibited. This led to the adoption of external pipe systems and quick couplers. Before factory systems were standardised, some operators used aftermarket quick-release kits (e.g. by Slewtic).

Optional Loader Accessories

• Levelling bar (keeps two points of attachment parallel at all lift heights)

• Pallet fork assembly

• Quick-release system for bucket/fork attachments

• Loader stand (for storage when removed)

Inspection Tips Before Purchase

• Check hydraulic rams for rust, pitting, or damage to chrome surfaces

• Inspect seals for oil leaks

• Examine hydraulic hoses for wear or cracking

• Pay attention to bracket and pin hole wear, especially at mounting points - pin holes typically wear more than the pins themselves

With thanks to Powerrabbit for the original detailed overview.

Preliminary Checks

• Fuel supply: Ensure the tank is adequately filled – running out of fuel is a common reason for needing to bleed the system.

• Manual: Keep your tractor manual nearby for reference. Diagrams for typical fuel systems with in-line and rotary (CAV) pumps are included for guidance.

Bleeding Procedure – 4 and 6 Cylinder Engines

1. Prime the system using the fuel lift pump

• Begin by hand-operating the fuel lift pump.

• Open the bleed screws on top of the fuel filter housings one at a time, starting with the one closest to the fuel tank.

• Pump until fuel flows out without air bubbles.

• Tighten the screws gently – the housings are aluminium and easily damaged.

2. Bleed the injection pump

• Open the bleed screws on the injection pump.

• Continue priming by hand using the lift pump.

• Since the injection pump is on the opposite side of the engine, it may be difficult to see – get assistance if possible.

• Once air-free fuel flows from both screws, tighten them.

3. Bleed between the injection pump and injectors

• Loosen the fuel delivery pipe nuts on one or two injectors (two adjacent ones for 6-cylinder engines).

• A few turns will do – just enough to lift the pipe off its seat so fuel and air can escape.

4. Start the engine

• Use the starter to crank the engine; if cold, use the thermostart.

• Once the engine begins to fire:

  • For 4-cylinder: tighten the loosened injector pipe and crank again until it starts. The remaining cylinders should follow.

  • For 6-cylinder: tighten one injector pipe when it begins to fire, then tighten the other as it continues running. The engine should smooth out as all cylinders fire.

5. Inspect for leaks

• Let the engine run while checking all pipes and bleed screws for leaks.

• Reinspect them during the next 10 hours of operation.

Bleeding Procedure – 3 Cylinder Engines 3-cylinder engines typically require a simpler process:

1. Clean the sediment bowl

• Remove and clean the bowl and gauze.

• Inspect or replace the rubber seal if necessary.

2. Reassemble and refill

• Refit the sediment bowl and screw up the yoke loosely.

• Allow it to fill and overflow, then tighten it and clean up any spilled fuel.

3. Service the fuel filters

• Remove both fuel filters, clean the bowls, and fit new filters with fresh ‘O’ rings and seals.

• Locate the 9/16" hex head on the filter housing (near the tank side); this bleeds both filters.

• Loosen this screw and pump the lift pump by hand until fuel flows without air.

• While pumping, tighten the bleed screw as fuel is expelled.

4. Final steps

• Wipe down the system.

• The engine should now start without bleeding the injection pump.

• Run at approximately 1100 RPM for five minutes, then inspect for leaks.

Reference Diagrams

• Example A: 4-cylinder fuel system with in-line injection pump

• Example B: System with a rotary (CAV) pump

(Refer to manual or schematic diagrams as needed.)

This guide is adapted from a David Brown (Canada) service bulletin and is primarily based on DB 990 A & B models, though other models are referenced. It is not a comprehensive manual, but it may help in diagnosing hydraulic faults. Please email admin with any questions or feedback.

Thanks to Ivan (DB 770, DB 880) for supplying the information.

Initial Checks

1. Remove Covers
   

   • Take off the small top cover above the valve chest (on the axle) and the rear cover on the right-hand ramshaft bracket.

1. Start the Engine
   

   • From behind the tractor, observe the rear opening (pipe #915339).

   • In External Services position, oil should flow steadily from the pipe if the pump is working.

1. Operate the Quadrant Lever
   

   • Pull the lever into the Select position.

   • If oil flow stops, the bypass valve has seated correctly — system is functioning up to this point.

   • If oil continues flowing, the bypass valve has not seated.
     

     • Momentarily switch to Height position (with links down) to check if the abutment plate is obstructing the spool valve. Then return to External Services.

Possible Causes of Bypass Valve Not Seating

• Spool valve not fully dropping into lift position

• Spool valve sticking in its sleeve

• Dirt in the bypass screen or blocked .020" washer hole

• Tight spot in valve movement – may need lapping with jeweller’s rouge through full rotation

Hold Valve Check

• With the quadrant still in Select and bypass valve seated, look forward through top plate #910182.

• At ~1000 RPM, if a jet of oil emerges from the indicated slot, the hold valve is not seating.

Possible causes:

• Tip hole of the hold valve is blocked

• Tight spot in valve or bore – may require lapping

• Shock load relief valve (item 10, p.54) may be leaking — visible from the top of the valve chest

Additional Leak Checks

1. Remove Plate #910860 from front of quadrant housing
   

   • Lever in Select, inspect with good lighting for leaks:
     

     • From plugs under hold and bypass valves (held with circlips)

     • From O-rings (item 32, p.54) between pipe #915687 and valve chest

     • From pipe #915687 itself – check for cracks or splits

1. Check 3-Point Hitch Cylinder (#910107)
   

   • If no visible external leaks, test pressure at the cylinder inlet using a gauge.

   • Low or no pressure? Possible leak or split in pipe #928511 or a loose union.

Pump Pressure Testing

1. All models (except 1200)
   

   • Test at item #25 using a pressure gauge and blanking plug #961977 (see p.23 of the service manual).

   • This isolates the system down to the pump, relief valve, and pipe #915684 (with O-rings).

1. Model 1200
   

   • Quick test via stack valve.

   • Full procedure is detailed on page H5 of the special tools list.

Important System Notes

• In External Services, the quadrant lever and abutment plate are active.

• The sensing unit, cable, sensing pushrod, cam, and cam-operated pushrod are not part of the system in this mode.

Common Fault Scenarios

Scenario 1:

• Lever in Select/Height/Depth, main relief valve blows

• Implement does not lift

• No oil pressure at cylinder inlet (#910107)

• When moved to Drop, the valve stops blowing Likely Cause:

• Non-return valve seal has blown out – valve chest replacement required

Scenario 2:

• Lever in Lift, implement raises fully but continues to blow relief valve

• In Hold, pump keeps running (relief valve continues to blow)

• On stopping engine and selecting Drop, implement remains raised Likely Cause:

• TCU valve seat has blown out – prevents pressure release

• Valve chest replacement typically required

This guide provides a structured method for tracing hydraulic issues. While not exhaustive, it offers practical diagnostics for common faults.

Before Renovation Before stripping the paint from your bonnet, take time to measure and record the exact position of the original stickers. This will ensure accurate placement of the new ones. Keep your notes somewhere safe for future reference.

Removing Old Stickers A hot air gun is often the easiest way to remove existing stickers. Apply gentle heat to soften the adhesive without damaging the paint beneath. After removal, use an appropriate surface cleaner to eliminate any remaining adhesive residue.

Surface Preparation Proper preparation is key to a professional, long-lasting finish.

• Stickers are usually applied after a repaint or full renovation.

• Ensure any fresh paint, particularly enamel, is fully cured before applying stickers.

• The surface must be smooth, dust-free, and free from grease or solvents—any imperfections will show through the vinyl.

Ideal Temperature The temperature of both the bonnet and stickers should be between 15°C and 25°C. Avoid applying in direct sunlight or cold conditions:

• Too cold: Stickers may tear or fail to adhere properly.

• Too hot: Vinyl may become too soft and stretch or distort.

If needed, move the bonnet into a heated workspace to maintain a stable temperature.

Applying the Stickers Two Application Methods: Wet or Dry

Dry Method

1. Use masking tape to position the sticker according to your reference notes.

2. Peel back about an inch of the backing paper.

3. Using an applicator (a credit card wrapped in a soft cloth works well), press the exposed section of vinyl onto the bonnet, pushing air outwards.

4. Remove the masking tape.

5. Gradually peel away the backing paper, keeping the loose part of the sticker under gentle tension and just above the surface. Do not remove the full backing at once—it can cause creases or misalignment.

Wet Method

1. Mix water with a small amount of washing-up liquid (approx. 5%) in a spray bottle.

2. Lightly mist the bonnet area to create a thin film.

3. Apply the sticker without masking tape, using the moisture to slide it into position.

4. Use your applicator to press out the water from the centre toward the edges.

5. Allow the sticker to dry for at least 24 hours before driving the tractor to prevent it from shifting due to vibration.

Note: Avoid applying stickers with the wet method on hot surfaces—the soapy water will evaporate too quickly, reducing positioning time.

Stickers with Application Tape On David Brown models from 1974 to 1980, bonnet stickers are cut-letter vinyls rather than printed panels. These use application tape (similar to masking tape) to maintain correct positioning during application.

• Apply these using the dry method only.

• Once in place, press down firmly to ensure adhesion.

• Carefully peel away the application tape, leaving only the lettering on the bonnet.

Helpful Tips

• Store stickers in a dry place; roll longer stickers loosely to prevent creasing.

• Allow stickers and bonnet to warm naturally to room temperature—do not use direct heat.

• Never apply cold stickers to cold surfaces.

• For large stickers, never remove all of the backing at once—work gradually.

Troubleshooting

Air bubbles? Use a fine needle to puncture the centre of the bubble and press the air outwards using your applicator.

Caring for Your Stickers

• Avoid pressure washing or steam cleaning near stickers.

• Wash by hand with warm water and a mild car shampoo.

• Use a soft sponge rather than brushes, which may cause scratches.

This guide is designed to help you achieve a clean, professional finish when applying new bonnet stickers. Patience and preparation are key—take your time, and you’ll get great results.

On the Cropmaster, 25, and 30 models, serial numbers were not stamped directly into the castings. Instead, raised date-coded letters and numbers were typically found underneath the gearbox housing. More commonly, serial numbers were stamped onto an identification plate located on the dashboard panel. If this plate is missing, accurately determining the serial number can be difficult.

The practice of stamping serial numbers directly into the castings began with the introduction of the 900 series. From that point, the serial number was stamped into the horizontal section of the front casting (often referred to as the “tombstone”), just behind where the radiator mounts, or slightly to the rear of the bonnet side panel. This method continued across the Implematic, Selectamatic, and the 9, 12, and 14 series tractors.

On 90 series tractors, the serial number is stamped on the top of the engine chassis casting, directly below the lift pump.

For engine identification:

• On 3-cylinder engines, the engine number is stamped approximately halfway up the block, behind the drive connection for the rev counter cable.

• On 4-cylinder engines, the number is stamped at the front of the block, just below the dynamo or alternator.

The engine designation begins with a code such as AK/4 or AD/4, which identifies the engine type. For 3-cylinder engines, the designation typically begins with 55/1. The numbers following this prefix represent the individual engine serial number.

With thanks to Powerrabbit for providing this detailed information.

Based on several discussions on the forum, it appears that many members experience hydraulic lift issues—particularly after an oil change. Often, these problems are not due to mechanical faults or valve chest issues, but rather the presence of air in the hydraulic system. The following guidance can help avoid unnecessary dismantling by properly bleeding the system.

Background

On Livedrive models, the hydraulic pump operates continuously as soon as the engine starts. Because there’s a delay before the new oil reaches and circulates through the pump, this is the moment when air may be drawn into the system—causing erratic lift function.

Recommended Bleeding Procedure (After Oil and Filter Change)

• Start the engine and run it at approximately 1000 RPM with the hydraulic lever in the fully lowered position.

• Locate the hexagon plug on the top of the casting often referred to as the "camel’s hump"—this is the rearmost plug on the highest part of the casting between the quadrant and the seat, on top of the rear axle.

• With the engine running, raise the hydraulic lever fully to the rear until oil (free of air) begins to flow from the plug. Once the oil runs clear, re-tighten the hexagon plug.

• Move the lever back to the hold position (midway on the quadrant).

• Locate the bleed nipple (it resembles a large grease nipple) positioned behind the 3-way valve unit, on the clutch pedal side of the tractor. This nipple can often be obscured by dirt as it sits in a recessed area facing forward, where the axle casting curves downward into the valve block.

• Slacken the nipple slightly and again raise the hydraulic lever until oil flows without air. Once the oil runs clear, tighten the nipple before releasing the lever.

In some cases, the process may need to be repeated if there is a significant amount of air in the system, but usually, one careful cycle is sufficient to restore normal operation.

With thanks to Powerrabbitt for the valuable contribution.

885 PAGE 1

885 PAGE 2

1200

1490 & 1690

Explanation provided by DBTC member “Erkki”

At the core of the rotary fuel pump is the rotor and rotor housing (part 39). The rotor operates similarly to a distributor in a petrol engine. It rotates within the housing, which has ports aligned with each injector line. When the hole in the rotor aligns with the corresponding hole in the housing, fuel is delivered to the appropriate injector.

Located above the rotor are two rollers, positioned opposite each other. Between these rollers are bearing plates, and beneath them sit two high-pressure pistons that move toward and away from each other inside a bore within the rotor.

The rollers move along a cam ring (part 57). On the smooth sections of the cam ring, the rollers are farther apart, allowing the pistons to draw in fuel. As the rotor continues to turn, the rollers reach raised cam lobes. When they pass over these lobes, they are forced inward, pushing the pistons together. This compresses the fuel between them, generating high pressure, and sends a fuel charge to the injector line.

To allow the pistons to move apart on the smooth part of the cam ring, the pump requires an internal pressure, known as interpressure, within the housing. This is generated by a vane-type (cross-blade) pump located at the rear of the injection pump. The blades (part 34) rotate inside housing 36, which is slightly off-centre relative to the rotor shaft. This eccentricity causes the blades to slide in and out of their slots, creating fuel flow and internal pressure.

Interpressure is regulated by a mechanical valve (part 18A), ensuring it stays within the correct limits.

The throttle control is managed by a small rotary valve (part 182). This valve regulates how much interpressure reaches the high-pressure side of the system. In one extreme position, it blocks the pressure entirely; in the other, it allows full flow. Between these extremes, it adjusts the amount of fuel delivered—this is controlled by the throttle pedal and a mechanical governor located at the front end of the rotor.

If you are a member of DBTC, have a tractor and don’t know the original registration number, the Club may be able to help.

Please get in touch with David Throup/Jack Beevers who will assist you in the process at :

tractor-registration@dbtc.co.uk

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