Symptoms
Ticking valves, or it's simply due: the factory schedule says every 5,000 miles.
The fix, step by step
- Adjust with the engine cold and parked facing downhill, so oil drains forward off the head.
- Remove the cab engine covers and the valve-cover clearance plate, the plug leads, cap and rotor, the plugs, the breather and the cover (it takes some wrestling to get out).
- Turn the engine over and set each valve with a feeler gauge: cold, inlet 0.10 mm and exhaust 0.20 mm.
- Check worn rockers, because a groove can make the gauge read wrong.
- Replace an adjuster that's loose on its base.
Tools & part numbers
- 14 mm crow's-foot wrench
- 13 mm socket
- 0.10 and 0.20 mm feeler gauges
- 13/16-in deep socket for military plugs. Expedition Imports warns that old-style heads use short-reach plugs and new-style heads long-reach, and the wrong one destroys the threads.
Where to buy the parts
Unimog 404 valve cover gasketExpedition Imports ↗Amazon ↗
NGK spark plug BPR5ESExpedition Imports ↗Amazon ↗
Hunting a used or discontinued part? Search eBay Motors for Mercedes-Benz Unimog 404 parts →
Rated for a competent home mechanic with a decent tool kit. Confirm torque figures, fluids and procedures against the factory service manual for your VIN, support the truck on stands rather than a jack, and work at your own risk (disclaimer). Some parts links are affiliate links, which pay us a small commission at no cost to you.