I have a 2008 Seat Leon FR TDi and need to change one of the fuel pipe (which has become torn slightly). The hose is ~ £50 + VAT so I am keen to do it correctly.

Can anyone advise if the fuel in my car is under pressure and if I would be able to change this hose without getting a face full of diesel?

The hose is the bottom on in this picture (blue band).

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Leon Engine Bay

  • "The service manual of your automobile should provide you with easy step-by-step guidance to do this [depressurize the engine] successfully." -Website
    – E.V.I.L.
    Feb 7, 2014 at 19:05

3 Answers 3


This hose is a low pressure one. Your PD type engine only has high pressures inside the valve cover. There is a low-pressure lift pump in the tank, however, which might make a little spritz of a leak when you first remove the hose.

You can depressurize the 'low pressure' side of the system by opening the water separator on the bottom of the fuel filter (to the left of the frame of the photo you took; located at the other end of the hose in question). If for some reason this is inaccessible (some filters don't have it) you could just wrap a rag around the hose after you remove the clamp, and twist and pull to remove. The rag will be more than adequate to absorb any initial pressure release.

You're not in any grave danger. One look at the type of clamp on the hose should provide that much information. Keep the fuel system nice and clean, and when you go to start it the first time cycle the key switch a few times before going to crank it up. This will let the in-tank pump purge out any air you introduced.

  • Thanks for this. I have changed the hose now, however I think I have air trapped in the system. I drove the car 10 miles earlier and it was choking heavily at times, particularly going uphill. I see two valve-looking caps to the left of the fuel filter. Would opening one of these up help remove the trapped air? Should I do it when the engine is running?
    – crmpicco
    Feb 8, 2014 at 15:35

Diesel fuel system has (extremely) high presure between the injector in the engine and the pump.

It has pressure in the normal fuel lines too, but not that large. After the change do not forget to remove the excess air from the fuel line!


  • Yes, this was my concern really. As the fuel line is between the injector and the pump I was concerned about pressure. Do you believe this is safe to change myself? On the face of it the change seems pretty straightforward. Remove the two clips and re-fit the new hose, then clip it on again. Also, how do I remove excess air from the fuel line after the change?
    – crmpicco
    Feb 3, 2014 at 15:36
  • Do you know anything about the air release?
    – crmpicco
    Feb 8, 2014 at 15:38

as mentioned fuel pressure between injector and pump is high;can exceed 20,000p.s.i. and literally cut your finger off or blind you.Same result as cutting steel with water. Workshop manual online or from local library (possibly) is a good resource

  • 1
    While this is a true statement it doesn't address the specific question asked. We are looking for specific answers to specific questions. Apr 9, 2014 at 15:25

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