So....

My 3.0L V6 with about 130 000 miles is giving me problems. It began with a blown coolant hose....one that goes to the heater core. I replaced this hose, and now the motor has overheated once, and I even heard some detonation (pinging). I shut it down and had it towed home. The next time I started the truck up it idled very high?

I replaced the thermostat, because it was easy, inexpensive, and I've never changed one before, and wanted to give it a try. The truck is still overheating.

Here are the the facts:

1) when I squeeze the upper rad hose (where coolant flows into the rad) it is very very firm, and hot. So firm, that I can barely squeeze it. My repair manual says I should be able to squeeze it, let go, and hear coolant refilling it. I don't hear this happening. The manual says this is a sign of a bad water pump.

2) After about 4 minutes of running, the temp climbs very quickly, and it climbs into the hot zone, so I shut it down.

3) I checked the rad, and there seems to be no coolant in it. I topped it up with about a litre of coolant. This did not seem to help.

4) About 6 months ago, the heater fan stopped working. It was intermittent at first, then eventually stopped altogether. I haven't fixed this.

5) I have grabbed onto the water pump shaft (the one that is in the center of the fan) and attempted to wiggle it up and down to check for play. NO PLAY. The manual says if there is play than that could be a faulty water pump shaft.

6) Since I've owned the vehicle (2 years, about 30 000 miles) I have noticed that it goes through alot of coolant...about 1 litre every few thousand miles) There were never any signs of leaking.

7) My oil is not milky, so I'm hoping it is not head gasket related

So I'm thinking it is a clogged radiator or the water pump. ARE THERE ANY OTHER CHECKS OR TESTS I CAN DO TO NARROW IT DOWN FURTHER? Can I put a hose on the top of the rad, and open the drain on the bottom of the rad and see if there is flow from top to bottom?

Any help would be great!