Flushing closed system and fan sensor help

I am getting ready to put all new hoses on my 1990 XJ Laredo and I need some advice on flushing the system. I am going to use the Prestone that you leave in for several hours while driving but am baffled at how to get the stuff into the system. Can you just add it throught the bottle or should I try to introduce it in some other fashion? Also, I am going to replace all my sensors while the fluid is out of the block and radiator but I am having a hard time finding the fan sensor that goes into the radiator. Could anyone give me a heads up on where to pick one up. I tried Rock but they do not have this one.Thank you for the help.

convert to the open system! Easy to do, and very cost effective. My 89 was converted and is doing great. get an 1995-9 XJ radiator, adjustable fan control, 5/8 heater hose, new t-stat, and a little creativity to convert your coolant bottle into a resivor.

I am getting ready to put all new hoses on my 1990 XJ Laredo and I need some advice on flushing the system. I am going to use the Prestone that you leave in for several hours while driving but am baffled at how to get the stuff into the system. Can you just add it throught the bottle or should I try to introduce it in some other fashion? Also, I am going to replace all my sensors while the fluid is out of the block and radiator but I am having a hard time finding the fan sensor that goes into the radiator. Could anyone give me a heads up on where to pick one up. I tried Rock but they do not have this one.Thank you for the help.

They are readily available at local autoparts stores

http://www.autozone.com/selectedZip,92647/initialAction,partProductDetail/initialpartType,00115/initialR,270609/initialvehicleId,1638702/shopping/selectZip.htm