VAN LIFE FIELD GUIDE

7 Common Mercedes Vito Problems on a Road Trip
(And How to Fix Them)

The Vito drives like a car, not a van. That is its biggest strength and the reason it is so popular for camper conversions. But the Mercedes engineering that makes it refined also makes it expensive when things go wrong. Here is what to watch for, and what to do when it happens.

This guide covers both the W639 (2003 to 2014) and the W447 (2014 onwards). Most of the diesel problems apply to both generations since they share variants of the OM646 and OM651 engine family. The W447 fixed the worst of the W639's rust issues but introduced its own complications with emissions equipment. Everything below is sourced from documented owner experiences on benzworld.org, mbclub.co.uk, PistonHeads, and specialist Mercedes diesel mechanics.

In this guide:

1. Injector Seal Failure ("Black Death")
2. DPF Regeneration and Clogging
3. Rust (W639 Especially, but Not Only)
4. Timing Chain Wear
5. Automatic Gearbox Hesitation (7G-Tronic)
6. Electrical Gremlins and Battery Drain
7. Suspension and Steering Wear

1. Injector Seal Failure ("Black Death")

You notice a strange chemical smell inside the cabin, particularly when idling or at low speed. When you pop the engine cover, you see a thick, black, tar-like crust building up around one or more of the fuel injectors. This is what Mercedes owners call "Black Death," and it is one of the most well-documented problems across the entire CDI diesel range.

Why It Happens

Each fuel injector sits in the cylinder head and is sealed by a small copper washer. Over time, this washer erodes from the extreme heat and pressure of the combustion chamber. Once the seal is compromised, combustion gases escape past the injector and carbonise on contact with the cooler metal of the engine block. The result is a rapidly growing mass of hardite-like carbon deposit around the affected injector. Left untreated, the carbon welds the injector into the head, making removal exponentially more difficult and expensive.

This affects W639 models more severely, particularly pre-2006 units with the OM646 engine, but the OM651 in later W639s and early W447s is not immune. Forum members report the issue appearing anywhere from 80,000 to 200,000 km depending on driving conditions and fuel quality.

The Fix

Early stage (small amount of black residue, no performance loss): Remove the engine cover and inspect all four injectors. If you catch it early, the fix is straightforward. The injector is extracted, the seat in the cylinder head is cleaned using a reaming tool, a new copper washer is fitted, and the injector is reinstalled with a new stretch bolt. Copper washers cost almost nothing. The specialist tool to clean the seat runs about 20 to 40 euros online. Many Vito owners do this themselves with basic hand tools and a torque wrench.

Late stage (heavy carbon buildup, chuffing noise, rough idle): The injector may be seized into the head. A specialist injector puller tool is required. If the carbon has been building for a long time, the injector can snap during removal, requiring the head to come off for extraction. At a dealer, this can run to 1,500 euros or more per injector. At an independent Mercedes specialist, roughly half that. The lesson is clear: check the injectors every service, and replace the copper washers proactively at 100,000 km even if they look fine.

Prevention on the road: Carry a spare set of copper injector washers, stretch bolts, and a small tube of ceramic anti-seize grease. If you catch the first sign of black residue during a routine check, you can deal with it at a campsite with basic tools before it becomes a head-off job.

2. DPF Regeneration and Clogging

The DPF warning light appears on the dashboard, sometimes accompanied by reduced engine power. The van feels sluggish and unresponsive. Fuel consumption climbs noticeably. In the worst case, the engine goes into limp mode and limits you to about 2,500 RPM.

Why It Happens

The Diesel Particulate Filter captures soot from the exhaust and periodically burns it off through a process called regeneration. Regeneration requires sustained driving at higher RPM and temperature, typically 20 to 30 minutes at motorway speed. If your driving pattern consists mostly of short urban trips, stop-start traffic, or low-speed campsite-to-campsite hops, the DPF never reaches the temperature needed to regenerate. Soot accumulates until the filter is blocked.

This is particularly relevant for van life because many overlanders drive short distances between campsites and then idle for extended periods with auxiliary equipment running. The engine never gets hot enough to clean itself. The problem is worse on the W447's Euro 6 engines, which have more aggressive emissions equipment including AdBlue injection alongside the DPF.

The Fix

If the warning light has just appeared: Drive the van on a motorway or fast A-road for 30 to 40 minutes in a gear that keeps the RPM between 2,500 and 3,000. Do not use cruise control. Keep the revs up. This gives the system the heat it needs to trigger passive regeneration. In most cases, the light will go out within 20 to 30 minutes of sustained driving.

If the light has been on for a while and performance is reduced: You may need a forced regeneration using a diagnostic tool. Any Mercedes dealer or independent specialist with a Star Diagnosis (or Xentry) system can initiate this. The engine idles at elevated RPM for 20 to 30 minutes while the system injects fuel to raise exhaust temperatures. Cost is typically 50 to 150 euros. Some owners invest in an iCarsoft MB V2.0 or similar OBD2 scanner that can trigger DPF regeneration, which pays for itself after one use.

If the DPF is completely blocked: It may need professional cleaning (chemical flush or thermal cleaning, 300 to 500 euros) or replacement (1,000 to 2,500 euros at a dealer). Prevention is everything: build at least one motorway run of 30 minutes into every week of driving, even if your itinerary does not demand it.

3. Rust

The W639 Vito has a well-documented reputation for corrosion, particularly on white and non-metallic paint finishes. Wheel arches, door bottoms, the loading bay floor, and the area around the sliding door rail are the most common trouble spots. This is not a minor cosmetic issue. Structural corrosion in the sills and wheel arches can compromise the vehicle's integrity and fail an MOT or equivalent roadworthiness inspection.

Why It Happens

The W639 was built in Vitoria-Gasteiz, Spain. Owner forums contain persistent reports that non-metallic (solid colour) paint received only a single coat of primer and a single coat of gloss, while metallic finishes received etched primer, base coat, and lacquer with a baked finish. This means white Vitos, which represent the majority of commercial models, are significantly more susceptible to corrosion. The W639 facelift from around 2010 to 2012 improved matters somewhat, and the W447 (2014 onwards) is generally considered to have resolved the worst of the rust issues, though wheel arch corrosion is still reported on higher-mileage W447s.

The Fix

Before buying: Inspect the wheel arches (inside and out), the bottom edges of all doors, the sliding door rail channel, and the underside of the sills. Use a magnet to check for filler. If the van is white and pre-2012, be extra suspicious. Bubbling paint, brown staining on the inner wheel arch liner, and soft spots when you press the metal are all signs that corrosion has already started from the inside.

Prevention: Apply a wax-based underbody protection (Dinitrol, Bilt Hamber, or similar) annually. Treat the inner wheel arches with cavity wax. Keep the sliding door rail clean and lubricated. If you are overlanding in winter or on salted roads, wash the undercarriage after every trip.

If rust is already present: Small surface rust on cosmetic panels can be treated with a rust converter and re-sprayed. Structural rust in the sills or wheel arches requires cutting out the affected metal and welding in new sections. This is a job for a body shop, not a campsite. Budget 500 to 1,500 euros per panel depending on severity and location.

4. Timing Chain Wear

You hear a rattling or chattering noise from the back of the engine, most noticeable during cold starts or when the engine is under light load. The noise may come and go. Over time it becomes more persistent. If left long enough, the chain can stretch or skip, causing catastrophic engine damage.

Why It Happens

The OM646 and OM651 diesel engines in the Vito use a timing chain rather than a belt. In theory, a chain should last the life of the engine. In practice, the chain, guides, and tensioners wear out, particularly in the OM651 where the chain is located at the rear of the engine (the transmission side) rather than the front. This rear placement makes replacement significantly more labour-intensive than a typical timing chain job, because access requires separating the engine from the gearbox or dropping the subframe.

Owner reports from CarsGuide and multiple Mercedes forums indicate that chain wear typically surfaces between 100,000 and 200,000 km. The OM651 is more prone than the earlier OM646. The issue is not the chain itself but the plastic guides and the hydraulic tensioner, both of which degrade faster than the chain and allow it to develop slack.

The Fix

If you hear the rattle: Do not ignore it. A stretched or slack timing chain can skip teeth and destroy the engine. Get it diagnosed immediately. A Mercedes specialist will typically listen with a stethoscope and check chain tension with a diagnostic tool.

Replacement: The chain, guides, and tensioners are replaced as a kit. Because of the rear placement on the OM651, labour is the dominant cost. Expect 1,500 to 3,000 euros at an independent specialist, or significantly more at a dealer. The parts kit itself is typically 200 to 400 euros. This is not a roadside fix. If the rattle starts during a trip, drive gently to the nearest specialist. Do not rev the engine hard and do not ignore the noise.

Prevention: Use the correct Mercedes-specification oil (229.51 or 229.52, low-SAPS synthetic) and change it on schedule or earlier. Cheap oil or extended drain intervals accelerate chain and tensioner wear. If you are buying a used Vito with the OM651, ask whether the chain has been done. If nobody knows, budget for it.

While you are sorting the mechanicals, sort the accessories. No drilling required. View magnetic accessories

5. Automatic Gearbox Hesitation (7G-Tronic)

The van hesitates or jerks when changing gears, particularly from first to second and when the gearbox is cold. Shifts feel rough or delayed. In some cases, the gearbox slams into gear with a noticeable thud. The problem is usually worse in the morning on the first few gear changes and improves once the transmission fluid warms up.

Why It Happens

The 7G-Tronic (722.9) automatic gearbox used in the Vito is fundamentally the same unit found in Mercedes passenger cars. It is a good gearbox, but it relies on clean, properly specified transmission fluid to operate the hydraulic valve body that controls gear selection. Mercedes originally marketed the fluid as "lifetime fill," meaning it never needs changing. This turned out to be optimistic. Over time, the fluid degrades, loses its friction properties, and the valve body becomes sluggish. The result is rough, hesitant, or delayed shifts.

Fleet operators who run 80 or more Vitos have documented that gearbox problems are almost always linked to neglected fluid changes. Those who change the fluid and filter every 60,000 to 80,000 km report minimal gearbox issues even at very high mileages.

The Fix

Fluid and filter change: Drop the transmission pan, replace the filter, and refill with the correct MB 236.14 specification fluid. You do not need the overpriced Mercedes-branded fluid. Dexron III compatible ATF in the correct specification works identically. Budget 200 to 400 euros at an independent garage including fluid and filter. This single service resolves the majority of shift quality complaints.

If the problem persists after a fluid change: The valve body may need cleaning or replacement. This is a specialist job (800 to 1,500 euros). In very high mileage vans where the fluid has never been changed, the damage to the valve body may be permanent and the gearbox requires rebuild or replacement. This is why proactive fluid changes matter.

Tip from forum mechanics: Adding a transmission conditioner such as Lube Guard can help smooth out a high-mileage gearbox by cleaning the small passageways in the valve body. It is not a substitute for a proper fluid change, but it can help after one.

6. Electrical Gremlins and Battery Drain

You come back to the van after a day or two and the battery is flat. The central locking behaves erratically. Electric windows stop working or operate intermittently. Dashboard warning lights appear and disappear without obvious cause. The alternator warning light flickers at idle but goes away when you rev the engine.

Why It Happens

The Vito has more electronic systems than most commercial vans, which is part of what makes it feel like a car. But more electronics means more potential points of failure. Battery drain is one of the most frequently reported electrical issues across both generations. Common culprits include the SAM (Signal Acquisition Module), which controls many of the van's electrical functions and can develop faults that keep systems active when the van is off, the alternator voltage regulator (which can fail gradually rather than catastrophically), and aftermarket camper conversion wiring that has been tapped into the vehicle's electrical system without proper isolation.

The W639 is additionally prone to issues with the electric window regulators and the central locking system, both of which can fail without warning. These are usually component failures rather than systemic electrical problems, but they add up over the life of the vehicle.

The Fix

Battery drain: The first step is to measure parasitic draw with a multimeter. Anything above 50 milliamps with the van fully asleep (wait 30 minutes after locking for all modules to shut down) indicates a problem. Pull fuses one at a time while monitoring the multimeter to isolate which circuit is drawing power. Common offenders are the SAM module, the radio/infotainment unit, and aftermarket accessories that have been wired to permanent live feeds.

Alternator: A failing voltage regulator can undercharge the battery without triggering a warning light until the battery is too depleted to start the engine. If you are getting intermittent alternator warnings, have the charging voltage tested under load. It should read between 13.8 and 14.4 volts with the engine running and electrical loads on. Below 13.5 volts consistently means the alternator or regulator needs attention.

For van life builds: If you are running a camper conversion with a separate leisure battery system, make sure it is properly isolated from the vehicle's electrical system with a split charge relay or a DC-DC charger. Direct tapping into the Vito's wiring loom for aftermarket accessories is one of the most common causes of mystery drain and erratic behaviour. A DC-DC charger (Victron, Renogy, or similar) is the correct solution. It costs about 150 to 250 euros and eliminates the majority of electrical integration headaches.

7. Suspension and Steering Wear

You hear clunking or knocking over bumps. The steering feels loose or imprecise. Tyre wear is uneven, particularly on the inner or outer edges of the front tyres. The van wanders slightly at motorway speed and requires constant correction.

Why It Happens

One of the Vito's best features is its car-like ride quality, which comes from a suspension and steering system that is more sophisticated than most commercial vans. The downside is that these components wear out, particularly on vehicles that carry heavy loads or have been used on rough roads. The front lower arm inner bushings are the first to go, typically around 170,000 to 200,000 km. Lower ball joints, track rod ends, and shock absorbers follow. If the vehicle has rear air suspension (Viano/V-Class passenger versions), the air bags, pump, and valves can also fail.

Mercedes specialists who run large Vito fleets report that suspension issues become a routine maintenance item from around 200,000 km onwards, with individual components needing attention at each service interval.

The Fix

Diagnosis: With the van on a lift, have someone turn the steering wheel while you watch the track rod ends and lower ball joints for play. Grab each front wheel at the 12 o'clock and 6 o'clock positions and rock it to check ball joint and wheel bearing play. Then grab at 3 and 9 and rock to check track rod ends. Check the bushings visually for cracking or deformation.

Replacement: Front lower arms, bushings, ball joints, and track rod ends are all widely available as aftermarket parts and are straightforward to replace with basic tools and a press for the bushings. A full front suspension refresh (both lower arms, both track rod ends, both drop links, alignment) runs about 500 to 800 euros at an independent garage using quality aftermarket parts (Lemforder, Meyle HD, or TRW).

For overlanding and heavy loads: If your Vito is carrying a camper conversion with significant added weight, consider upgrading the rear springs or adding helper springs to prevent the rear from sagging under load. Sagging increases wear on all rear suspension components and changes the front geometry, accelerating tyre wear.

The Honest Summary

The Vito is a genuinely good van. Fleet operators who run dozens or hundreds of them consistently report lower cost per mile than Ford Customs and comparable or better reliability than VW Transporters. It drives better than both. The build quality inside the cabin is noticeably superior. It is a Mercedes, and on a good day it feels like one.

But it is also a Mercedes in terms of repair costs when things go wrong. The key to living happily with a Vito is proactive maintenance: change the gearbox fluid (even though Mercedes says you do not need to), check the injector seals regularly, give the DPF a proper motorway run every week, and address any timing chain rattle before it becomes a timing chain catastrophe. The people who love their Vitos tend to be the people who maintain them properly. The people who hate them tend to be the people who bought a 150,000 km example with no service history and were surprised when it needed work.

If you are building a camper or overlanding rig on a Vito platform, you have chosen well. Just respect the engineering. It will look after you if you look after it.