radiator is only two years old, the low water light comes on then overheats. the temp rapidly fluctuates 20-40 degrees intermittently. coolant level is full. when checked hot I could see what seemed to be excessive particles floating in the reservoir.

 

Have you properly purged the system of air?

 

It was serviced at the dealer and it ran fine for a week no problems

 

Check the radiator when cold and report back.

 

Thermostat sticking? Debris on a/c condensor? BOTH fans working?

 

ok, so, replaced the thermostat, drained out the coolant and filled with water for now, coolant is expensive.. let it run and bled the lines. it ran down the road for a half an hour under the firs temp mark after 160. as soon as I stopped at the gas station it idled fine still under 210 mark. left gas station and the temp started spiking, pulled over and opened bleeder and lots of air. when the air was out temp came down again.....ran a little farther and temp spiked again...opened bleeder and alot more air came out again....seems as if air is getting back in somehow...

 

Sure fire way I always did it. Let it cool, drain the radiator, open the bleeder, and pour very slowly. when you see water comming out the bleeder you have it.

 

You cant properly bleed the system while driving!!! let the car get up to temp (whatever thermo temp you have) then open the bleed screw until there is a solid stream of water coming from it. You CANT get these cars hot they have Aluminum heads mated to a cast iron block. the two meatals take heat much differently and you will blow a head gasket if you havent allready, in which case you wont be able to bleed the system due to the leak. If I were you i would check the oil to see if you have made a milkshake.

 

This is one handy thing to have.

Amazon.com: Lisle 24610 Spill-Free Funnel: Automotive

 

I don't think it's so much as blowing a gasket as it is warping a head. Which is what happened to me when mine overheated years ago.

You don't want to open the bleeders with the engine running unless the system is completely full(even then...I feel it's not necessary when filled correctly). It has been my experience that if opened with a half full system the bleeders suck air into the system.

Using the spill free funnel above(I have it and it's awesome).....

• Protect the opti from water and coolant
• Make sure the coolant reservoir is filled to the full hot level.
• With the engine stone cold, open both bleeders.
• Fill the system until water starts steadily coming out the thermostat bleeder.
• Close that bleeder.
• Leaving the one on the top hose open, fill the radiator completely full.
• When coolant comes out the top hose bleeder in a steady stream, close the bleeder.
• Fire up the car, turn the HVAC heater fan wide open(heat setting) and set the temp to max hot.
• Let it warm up(rev the engine, every now and again, once the temp is above 180* to circulate the coolant and help purge air).
• When the thermostat opens, the coolant level will drop. Fill it back up....keep it full.
• Shut the car off once the temp reaches around 200* and let it cool completely down(don't let it get above 212* with the cap off...it will boil..ask me how I know!!!! Had a volcano for a minute or two...).
• Once cool, check the level in the radiator....you may have to top it off.
• Put the cap on it, drive it normally checking the radiator and reservoir level when the engine cools back off(stone cold). Do check it over the next week once daily. You may have to top off once...maybe twice at most(the over flow tank). I have had to top off only the over flow tank.....multiple "topping offs" should raise a red flag for system leaks.
  

Doing the above, there should be no need to screw with the bleeders trying to "purge" air from the system.