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Mercedes-Benz Vito: W639 OM646 2.2 CDI Injector Return Pipe and Seal External Fuel Leak

W639 OM646 2.2 CDI Injector Return Pipe and Seal External Fuel Leak is a common fluid leaks fault on the Mercedes-Benz Vito on the 2003–2014 cars, and we rate it critical. Putting it right costs $400 to $1,500 at New Zealand independent workshop rates. Below is what goes wrong, the symptoms to notice on a test drive, where to look, and what to ask the seller before you hand over any money. It is one of 16 documented faults on the Mercedes-Benz Vito.

Vehicle
Mercedes-Benz Vito
Engine
2.2L
Years
2003–2014
Fuel
diesel
System
Fluid Leaks

This page covers the Mercedes-Benz Vito as a model. Some faults only affect particular engines or build years — enter a plate below to narrow the list to one car.

All Mercedes-Benz Vito faults16 documented faults on this model

What you are looking at

A single common-rail diesel fuel injector photographed against a plain background.Example of the part — not this vehicle

A common-rail diesel injector. Contamination damages the nozzle at the tip.

Panoha · CC BY-SA 3.0 · Wikimedia Commons

What goes wrong

The OM646 2.2-litre CDI diesel in the W639 Vito develops external fuel leaks at the injector return pipe banjo fittings and injector copper seat seals. Fuel escapes from the cylinder head area and can run onto hot exhaust components, creating a fire risk. The failure is caused by age-related seal deterioration and weakened or over-tightened banjo fittings. This is a well-documented failure pattern on higher-mileage W639 vans and is a safety-critical inspection item.

What you would notice

  • Diesel smell from engine bay particularly after a hard run
  • Visible fuel weeping or dried fuel staining around injectors or return rail
  • Fuel visible running down the exhaust manifold
  • Smoke from engine bay after heat soak following shutdown

How to check it

Where to look. Top of cylinder head, injector return rail banjo fittings, injector copper seat seals

With the engine warm, open the bonnet and inspect the top of the engine carefully around all four injectors and the fuel return pipe connections. Look for wet fuel, dried staining, or sooty burn-off deposits. Check banjo bolt fittings on the injector return rail for seepage. Any fuel near exhaust components is a safety-critical finding requiring immediate attention.

Parts involved: Fuel injector.

What it costs to put right

$400 to $1,500 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

Ask the seller

  • “Has there been any fuel leak from the engine area?”
  • “Have injector seals or return pipe fittings been replaced?”
  • “Has the vehicle had any fire or smoke from the engine?”

Now check the Mercedes-Benz Vito you are actually looking at

Everything above is true of the model, and it is free. What it does not tell you is whether THIS car has been looked after: its odometer history and whether the reading has ever gone backwards, whether there is still money owing on it, whether it has been reported stolen, how many owners it has had and what it is really worth today. That comes from the official records for that plate. Enter the plate for the free details, or get the full history and a market valuation from $13.49.

Not sure what you would be paying for? See what a full KickTyres check includes.

Where this comes from

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.

Mercedes-Benz Vito buyer questions

Is w639 om646 2.2 cdi injector return pipe and seal external fuel leak serious on a Mercedes-Benz Vito?

We rate it critical and common on the Mercedes-Benz Vito. The OM646 2.2-litre CDI diesel in the W639 Vito develops external fuel leaks at the injector return pipe banjo fittings and injector copper seat seals. Fuel escapes from the cylinder head area and can run onto hot exhaust components, creating a fire risk. The failure is caused by age-related seal deterioration and weakened or over-tightened banjo fittings. This is a well-documented failure pattern on higher-mileage W639 vans and is a safety-critical inspection item.

How much does it cost to fix on a Mercedes-Benz Vito?

$400 to $1,500 at New Zealand independent workshop rates. That figure is for this job on its own. A car showing the symptoms on this page is usually worth either walking away from or negotiating down by at least the repair figure.

Which Mercedes-Benz Vito years are affected?

Our research records this fault on the 2003–2014 Mercedes-Benz Vito. Build dates move around, especially on imported cars, so treat the range as the years to look hardest at rather than a guarantee either way. The official records tell you the exact build and first registration date for the car in front of you.

How do I check for it before I buy?

With the engine warm, open the bonnet and inspect the top of the engine carefully around all four injectors and the fuel return pipe connections. Look for wet fuel, dried staining, or sooty burn-off deposits. Check banjo bolt fittings on the injector return rail for seepage. Any fuel near exhaust components is a safety-critical finding requiring immediate attention. Look here: Top of cylinder head, injector return rail banjo fittings, injector copper seat seals