Hissing from Engine

Hi chaps, I have one of those noisy fuel pumps that buses for 30 seconds then stops. I have learned to live with it.

Today whilst I was fitting new headlight bulbs I had the ignition on but had not started the freelander.

From under the engine covers I could hear a hissing sound that stopped as soon as the fuel pump stops.

Is this normal? What can it be?

It's a TD4

Thanks

Funnily enough I have the exact same thing as you, only noticed it today as I was testing my wiper motor with the ignition on - the hissing stops as soon as the low pressure pump does.

I did notice my high pressure pump (near where the hissing was coming from) looked suspiciously damp - here's hoping it's not connected..

I'll be curious to know if anyone elses Freelander also does this mysterious 'hissing'!