engine temp question

[hixsy]

hi, i sprung a coolant leak the other week and have been trying to get to the source of the problem but having no luck. I thought it would be a simple case of topping it up again running the engine and finding where it was leaking from but when i run the engine nothing leaks now from anywhere, its taking ages to get to temp now and the front radiator hardly gets warm, and seems to get warm to touch in certain places of it? ive undone the bleeder on the rad and its not letting no air out, just coolant.

Another thing ive noticed aswell when i put the heater on hot and blower on the temp drops a goods 1/4 ! is this right ? what does that mean?

ive also found is that there is a switch been put into my dash pod that switches on the radiator fan, im not sure what this means first impressions are that the fan dont kick in and the last guy has been doing it manually when in traffic etc, is it easy enough to fix it back to how it should be? when i use this switch for a few minutes the temp drops a lot too.

The engine is a 1.6d. does the coolant system work on the same principles as a petrol ? i.e. thermostat etc ?

thanks