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Autopapyrus · Mitsubishi Fuso Fighter (1987), 6D16
https://autopapyrus.com/guides/mitsubishi/fuso-fighter/clutch-hydraulic-fluid-replacement/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.

Mitsubishi Fuso Fighter (1987), 6D16: Clutch Hydraulic Fluid Replacement

The clutch on this truck is hydraulically operated. It consists of a reservoir and master cylinder at the pedal, a line or hose, and a slave cylinder (possibly with an air booster) on the clutch housing. Brake fluid is hygroscopic. Over time it absorbs moisture, darkens and makes the system work worse. You replace it by bleeding: the old fluid is pushed out through the bleeder on the slave cylinder. The exact procedure for this model and engine is not documented in open service sources, so what follows is the general principle proven on hydraulic clutch systems. Check the layout of the parts on your own vehicle by eye.

Difficulty: Medium Time: 40-90 minutes Steps: 13 Tools: Bleeder wrench (usually 8-10 mm, a precise fit, preferably a box-end wrench), clear hose, drain container, syringe or bulb for removing fluid from the reservoir, clean rags, a helper, jack and jack stands or an inspection pit

Part

  • 🔩 DOT 3 or DOT 4 brake fluid from a new sealed container, about 0.5-1 L (0.5-1 qt). Check the type and grade against the marking on the reservoir cap. If you find leaks at the clutch slave cylinder or master cylinder during the job, you will need their repair kits or complete replacement cylinders

Step by step

13 steps
  1. Park the vehicle on level ground, set the parking brake, chock the wheels and switch off the engine. If you need access from underneath, put the truck over an inspection pit or on solid jack stands. Never use a jack as the only support.
  2. Find the clutch fluid reservoir. It is usually next to the brake fluid reservoir or on the master cylinder at the pedal. Wipe the cap and the reservoir around it so no dirt gets inside.
  3. Find the slave cylinder on the clutch housing. It has a bleeder screw with a cap. Clean the bleeder with a brush and remove the cap. If the bleeder is seized, first treat it with penetrating oil and wait. It should have been tightened only lightly, so do not use heavy force or you will shear the bleeder.
  4. Use a syringe or bulb to remove the old fluid from the reservoir down to a level just above the outlet port. Wipe the reservoir walls with a clean lint-free rag. If there is sediment on the bottom, remove it.
  5. Fill the reservoir with new fluid up to the MAX mark. During bleeding, the level must never drop below the MIN mark, or air will get into the system. Top up after every 2-3 cycles.
  6. Put the clear hose on the bleeder and put the other end in a container with a small amount of fluid so that the end is submerged. This stops air from being drawn back in.
  7. Have your helper press the clutch pedal smoothly to the floor and hold it. Open the bleeder about half a turn and fluid will flow out. Close the bleeder before the helper lets the pedal up. Only after that is the pedal released. If the pedal is released with the bleeder open, air will be drawn back into the system.
  8. Repeat the cycle until clean, fresh fluid with no air bubbles comes out of the hose. A full fluid change usually takes 10-20 cycles, but the number depends on the length of the line. Keep watching the level in the reservoir.
  9. If the truck has an air-assisted clutch booster, check that the system has enough air pressure (on the circuit gauge). Low air pressure affects pedal effort. The fluid side is usually bled at normal pressure, but check the procedure for your vehicle against the plate or markings on the unit.
  10. Tighten the bleeder carefully. The torque is low: as a guide, 6-10 N·m (4-7 lb-ft), no more, and the exact value should follow the manufacturer's specification. Put the cap back on. Wipe fluid off the bleeder and housing, because it damages paint and rubber.
  11. Top up the reservoir to MAX and close the cap. Press the pedal 10-15 times. It should feel firm, with a clear stroke and no sinking. If the pedal is soft, repeat the bleeding.
  12. Start the engine, press the clutch and engage the gears one by one. They should engage without grinding and without delay. Check on a test drive: the clutch must disengage fully and not drag.
  13. Inspect the connections, slave cylinder, lines and hoses for leaks. Check the reservoir level after the test drive.

Common mistakes and warnings

  • Do not mix different types of fluid. Mineral fluids and DOT brake fluid damage each other's seals. If the reservoir cap carries a different marking, confirm the fluid type first. The fluid is toxic and attacks paint. If it gets on your skin or in your eyes, rinse with water. The clutch affects the handling of a heavy truck, so if you lack experience, if the fluid level drops quickly, or if the pedal stays soft no matter what you do, take the truck to a repair shop to have the cylinders checked. Dispose of the old fluid as hazardous waste. Never pour it down drains or onto the ground.
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