Crunch in 1st and 2nd but no others

[geordiejones]

Hi 4x4 lovers can you help me, i have a 2.5 tdi on a L plate which crunches every time i put it in first or second gear, but if i bleed the clutch its ok for ten mins then goes again. also after 15 mins the clutch pedal makes a gripping noise.
Iv replaced all the seals in the slave and master but it still does it, can anyone help please.
                            CHRIS

[Range Rover Blues]

They can be a bas*** to bleed but as it lasts for 10 minutes I'm thinking something is leeaking slowly, or the fluid is boiling.  

First and second share a synchro hub which is probably past it's best.