Coolant leak from plastic housing

[panason1c]

Hi,
I have a slow coolant leak from the plastic housing (with coolant pipes going into it) situated immediately below the diesel pump on the right of the engine, the leak appears to be between the housing and the engine block, the coolant is dribbling down onto the gearbox...........what is this housing and is it likely to just be a seal needs replacing?

Thanks

2004, polo 1.9 tdi sport

[panason1c]

Update.........

It was the plastic housing that the temp sender is pushed into and the housing large 0 ring just needed replacing.
All good now.