index show that engine is overheating

I have my van almost for a year and was very happy until I start having problem with my cooling system.Actually one of those day my car start overheating .
Well, fist off all I did change the thermostat( very uncomfortable,but I did it) - result,no changes.
I did change temperature-switch - same think,
I did check the water-pump - fine , I check the belt - fine too.
flash the radiator - nothing is not stopping engine from overheating.
I check the coolant level - same as it was few days ago,oil doesn't showing any mixing with coolant.
Well I took it to a dealer and they sad that it is head gasket and intake manifold,plus water-pump .O.k. ,but they lie to me about waterpump ,because I did check it and in case I put new one in.They ask $1700 to fix the problem - too match.
So,here a I'm with funny question - is there any one with same problem,because as we know that temperature switch once the coolant reach 215 degree have to give a signal on cooling fan relay and fans have to start spinning,but mine not spinning for some reason,but when I unplug temperature sensor they start spinning right away.
Car still running and I'm not loosing any power and car had a 72K miles on odometer.
I cannot figure out what actually causing my engine to overheat.

Well ,i'm back again and i see that not too many people have a lot of fun as did for a last two week's,but i have surprice news for my self and maybe for somebody who have some problem as i do.
Finaly i found the reason why my index is telling me that my engine is overheat,because it is showing me a fake reading.I went to Autostore and they told me to check the temperature all over my radiator and also the temperature of the coolant after the thermostat and guess what they where right. I let my car to run about 20 min and I sow my index show me that the engine is overheating and arrow reach the first red line when my fan's kick on and the first what I did I check the temperature and I hade 215 degree,so finaly i knew that nothing wrong with my engine and now i just have to calibrate my index or look up for short wire somewhere. Plus i have to replace O2 sencor hi come up too,hey,never know maybe hi can cause this problem too.
I will keep my post update in case if someone find it helpfull.

Is the guage actually going into the red? Or is the coolant boing over? Otherwise, not overheating. Engine goes up to mid 220 before fans kick on. Pressure cap on radiator keeps boiling point well above 230.

Well as I sad ,the gauge is going to the first red line and then fans kick on,but I still could not find the cause of this - something making the index showing me such overriding.I want to check the relay's and I find out today how I can do it:
Once you put the key in your ign/sw and turn it on(not to crank) you can fill with your finger's on the top of the relay's when they click ,It is few of them so I may have to do it couple times and hope this will help a little,list I will know that my relay's is o.k.

Well as I sad ,the gauge is going to the first red line and then fans kick on,but I still could not find the cause of this - something making the index showing me such overriding.I want to check the relay's and I find out today how I can do it:
Once you put the key in your ign/sw and turn it on(not to crank) you can fill with your finger's on the top of the relay's when they click ,It is few of them so I may have to do it couple times and hope this will help a little,list I will know that my relay's is o.k.


Try to flush the system with Zerex Flush Cleaner and run the car for a half an hour before removing the cleaner, then repeat the process many times until the water is clear, then refill with with Prestone antifreeze, this should clean the system completly and the temperature should be OK. This should work if you don't have any coolant leak at all.