Replacing an old block heater on a Kubota

[Luath]

Hi guys,

I've an old Kubota L4200 and I'd like to replace the existing block heater. I believe the replacement part has a 17mm hex nut but the existing component looks way larger, somewhere about 30mm. Do these things come with sleeve inserts? Also do I need to drain anything before removing the old heater?

Thanks in advance.

Dave.