Outer Limits 4x4 Board

My 1ltr stockman overheated on the way home from work today temp went up to the red when i got off the freeway (85km/hr).
Pulled over pinched someones water hose and drove home without incident.
Now for the weird part, i have a brand new alloy radiator fitted twice the size of a standard one thats never been over a 1/4 before.
I had a 4by in real black dusty conditions on sunday could this have clogged it up. There are no leaks or drips from underneath the car or radiator.
Could the waterpump propeller thingie inside be corroded ?
I really have no idea but i dont want to overheat in peakhour again any thoughts?

Could be the thermostate.

removed the thermostat and when checking for leaks found a watery oil puddle under the muffler. Great head gaske or cracked head.
I think it was from this last weekend.

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