I've got an oil cooler mounted on the oil filter assembly but it is not used at the moment. There are two 15mm water pipes ready to be connected but where do they go? I presume that one is tee'd in to the bottom hose but where does the other go?

Sounds like a heat exhanger, not just a cooler. Meaning that it will heat the oil when it's cooler than the water and cool it when its hotter.

Don't know your setup; if you have car engine and not heater, ideally you could use the connection for the heater.

If not I would put two t's after the water leaves the engine but before the thermostant. In order to get flow through the exchanger you will need to reduce the flowrate between the t's.

Makes sense?

Ermm I think so. My setup is a Duratec V6 with no thermostat (electric water pump) There is a heater feed straight from the block but that only flows when the heater is switched on. If I connect the exchanger to the heater it won't be working most of the time and will probably just boil the water inside.

I think that by the time your oil gets hot enough to boil the water your electric pump will have switched on anyway so I wouldn't worry.

Edit
Err - Sorry missread what you said but can't your feed to the oil cooler come before the heater flow valve?

[Edited on 16/3/07 by Ivan]