Land Rover Repair: Oil water mix, and gear oil light now coming on, land rover models, head gasket problem

Question
We have a 00 land rover discovery, it has over 100k in miles and while driving it - I turned the heat off and the cars oil light came on. We assume low on oil - but then with next few miles started to overheat.  _ drove it home not letting it overheat into the red zone.  - We changed the head gasket and all associated gaskets in that the head gasket kit. Also change all the bolts.  

Then while driving it again it overheated- no oil light this time.
Change the gaskets again.  Found it to be a lose intake manifold bolt.
now looks like it is still leaking alittle water into the oil  and the hot  gear oil light is coming on.
Has power and runs great but I am afraid dont want to hurt it.  

Can the radiatior allow the oil and water to mix.Does that have something to do with the gear box temp.  
If I run with heat on gear box tends not to heat up as fast.

I love my Rover and don't want to give it up -  

Answer
Some Land Rover models have an oil cooler in the radiator.  If so, the lines can crack allowing fluids to mix.  I suggest you check to see if you have that.

Also, the gearbox temp light is alomost always a false alarm in my experience here in the USA.  Gearboxes seldom overheat but the temp switches fail regularly.

As regards teh gaskets - you may have a liner problem, instead of a head gasket problem.  Read more on the Robison Service web site - I have 2 articles on that.