1. Timing failure – belt and chain left too long
The most common cause of DW10 and DW12 failure we see is the timing system. These engines use a timing belt and a timing chain, and both are often left far beyond their safe life. When the timing fails, valves hit pistons and the engine is usually finished.
We recommend replacing the timing belt and timing chain every 50,000 miles maximum.
2. Cheap timing kits
Not all timing kits are equal. We regularly see early failures from low-quality kits – including some China-made kits sold under well-known brand names. Always use a timing kit from a major manufacturer and check where it was made. Saving £50 on a kit can cost you an engine.
3. Timing fitted incorrectly
On the DW10 and DW12, the timing has to be set correctly in relation to the diesel pump. If it isn't aligned properly, the engine runs badly and the timing components are put under extra strain. This is a job for a mechanic who knows these engines – see the section for mechanics below.
4. Oil pump failure and bottom-end knock
Old oil wears the oil pump. Oil pressure drops, the crank and bearings aren't lubricated properly and the engine starts knocking from the bottom end. On PSA engines, aftermarket oil pumps do not last – we only fit genuine original oil pumps.
5. DPF and AdBlue problems
A blocked DPF or faulty AdBlue system causes repeated regenerations, dilutes the oil with diesel and can push the van into limp mode. These systems need checking regularly.
Warning signs to look out for
- Knocking from the bottom of the engine
- Oil pressure warning light, even briefly
- Rattling or whining from the timing side
- Rough running or loss of power after a timing belt change
- DPF or AdBlue warnings on the dashboard
If you see any of these, stop driving and get the van checked.
Our recommended service schedule for the DW10 and DW12
- Engine oil and filter: every 6,000 miles maximum
- Timing belt and timing chain: replace both every 50,000 miles maximum
- Timing kit: major brand only – check the country of manufacture
- Oil pump: replace at 60,000 miles with a genuine original pump, never aftermarket
- Water pump: always fit with a metal gasket
- DPF and AdBlue system: check at every service
For mechanics: timing belt replacement tips
- Set the timing to the first timing point, then rotate the engine to the next point and check the alignment with the diesel pump.
- The diesel pump has two marks – rotate until both marks line up.
- Always use a metal gasket on the water pump, not paper or rubber.
- Use a genuine oil pump if it's being replaced – aftermarket PSA oil pumps fail early.
Repair or replace?
Once the timing has failed or the bottom end is knocking, repairing your own engine usually means valves, a head, a crank and bearings – and weeks off the road. A reconditioned engine is often the faster and cheaper option.
Our DW10 and DW12 engines are stripped to bare block and fully rebuilt in our Kent workshop, with a major-brand timing kit, a genuine original oil pump and a metal water pump gasket fitted. From £2,000 +VAT, supply only or supply & fit.
FAQ
- How often should the DW10 / DW12 timing belt be changed?
- We recommend replacing both the timing belt and the timing chain every 50,000 miles maximum, using a major-brand kit.
- Why is my Boxer / Relay engine knocking?
- In most engines we see, a worn oil pump and old oil have starved the crank and bearings. Change the oil every 6,000 miles and replace the oil pump at 60,000 miles with a genuine part.
- Can I use an aftermarket oil pump on a DW10 or DW12?
- We don't recommend it. On PSA engines, aftermarket oil pumps fail early – always use a genuine original pump.
- What's the difference between the DW10 and DW12?
- The DW10 is the 2.0 BlueHDi used in the Boxer, Relay, Expert, Dispatch and SpaceTourer. The DW12 is the 2.2 BlueHDi (2,179cc) used in the Boxer, Relay and Vauxhall Movano from 2019. Both fail for the same reasons.