Diesel Pump Seal Leak Fix

Diesel fuel pump seals are usually made of nitrile butadiene rubber, or NBR. About 20% of an NBR seal is plasticisers: the compounds that keep it soft, elastic and durable. Over time they degrade, evaporate or leach out, and the seal turns brittle, loses its flexibility and shape, shrinks and starts to leak.

229's main ingredients are phenol esters, a class of chemicals first used in seal manufacturing to give rubber its elasticity, compression strength and long-term durability. The fuel carries them to the dry, hardened seals, where they penetrate the porous rubber and are gradually absorbed. That replaces the lost plasticisers and restores the seal's flexibility, volume and shape, and with them its ability to seal.

Most leaking seals aren't mechanically damaged, just dry and hardened with age. Where a seal is still intact but weeping or dripping fuel, 229 can often restore it. If a seal is damaged but not physically broken, 229 may not stop the leak completely, but it can substantially reduce it, and that's often an acceptable, cost-effective result.

Some leaks are substantial and need the pump replaced or serviced. Most are minimal, though, and if yours is like the one pictured at the top of the page, 229 is a logical first step before an expensive repair. It works especially well on older diesel engines, where seal fatigue is common but the pump otherwise runs normally.

It isn't an exact science: every leaking pump is different, with its own wear and seal condition. Customer feedback has been overwhelmingly positive, though, with most users reporting that 229 stopped their leak and kept the pump leak-free for years.

Replacing the pump means a reconditioned exchange unit, from $2,500, or a new OEM pump, $2,500 to $5,000 or more. Rotary pumps (such as the Bosch VE) are less complex and generally cheaper to rebuild; common rail pumps (such as Denso, or Bosch CP3 and CP4) are more advanced and significantly more expensive. A diesel mechanic will usually need the vehicle for at least two days to remove, replace and reprogram the pump, and some models take longer.

The dose depends on how bad the leak is:

• A minor leak or seep: 1 litre of 229 per 20 litres of fuel.
• A dripping leak: 1 litre per 10 litres of fuel.

1. Add 1 litre (one full can) of 229 to about 10 litres of diesel in the fuel tank.
2. Drive the vehicle back and forth a few times (your driveway will do) with a few firm stops, to splash-mix the treatment into the fuel. Then drive or idle it up to temperature, so the treated fuel reaches the pump.
3. Turn the vehicle off and let the treated fuel sit in the pump for about an hour.
4. Start it and let it idle for 10 minutes to re-pressurise the system, then switch it off again for another hour.
5. Keep repeating this through the day, re-pressurising the pump every hour.

The key is keeping the treated fuel in contact with the seals under pressure. If the pump isn't re-pressurised every hour, 229 can't fully infuse into the seals and restore their flexibility.

Most leaks are sealed within a day. If yours persists, carry on for another day, repeating as needed. How well it works depends on the condition of the seals.