When I go over a speed bumb im getting a hissing sound of front shockers is this normal.

Yes.

I'd be tempted to have a look at the dampers to be honest. Jack the front up and have a look at the fescalised portion of the strut to see if there is any oil on it. If so the seals could be goosed and the sound you are hearing is air being drawn into the strut or oil escaping. Sometimes you will hear the oil moving between the different areas in the strut but without hearing what you are hearing it is impossible to tell if its a leak or normal behaviour.

Ta much guys cars going in to dealers on monday for service I ll ask them to check it oot.

My OEM front dampers did this, but they were 7 years and 150k miles old. Replaced them with the Bilstein B12's and new top mounts and now it is silent.

My OEM front dampers did this, but they were 7 years and 150k miles old. Replaced them with the Bilstein B12's and new top mounts and now it is silent.

That's because your new bilsteins are high pressure gas charged. Not because there were anything wrong with the factory ones. Most low pressure factory struts/shocks make a hissing noise on speed-hump type obstacles.

Mine make this noise too but i hear it from the back aswell as the front

That's because your new bilsteins are high pressure gas charged. Not because there were anything wrong with the factory ones. Most low pressure factory struts/shocks make a hissing noise on speed-hump type obstacles.

Agreed, my shocks had had it though.