Air in diesel fuel pipes

[Actirouge]

Hi people,
Ok weird one for you, not really a Activa problem but it is on my 2.1td French mk2 Activa....So it has the lucas epic fuel pump renowned for being some what picky when it comes to air in the system. When the engine is off after 1 hr ish bubbles start to flow from the fuel pump towards the fuel filter and start to form a lovely large bubble ready to trip up the fuel pump when I want to start it the next morning. Has anyone had this happen to them and if so any pointers...I've checked fuel lines, changed fuel filter and seal and bled the system a lot....

[myglaren]

Did you check the leakoff pipes?

[Actirouge]

Yeah, I took of the top inlet manifold and checked them, they seemed good. But the problem is it's hard to see a crack just big enough for air. Is it possible for the air to go via the return pipes through the pump and out the feed pipe when the engine is off.

[myglaren]

I believe, from comments on the forum that it is. The leakoff pipes become hard and brittle with the heat. The end plug is sometimes a problem.