External Thermostat?
 

Last summer my temps seemed to be running rather high. On an 85 degree day doing casual 45-55 in 4th-5th my temps would creep to the 3rd hash mark and a little beyond. I believe the external thermostat is probably the culprit, however, right now temps here are in the 40's-50's so the car has no problems running steady temps.

After a good hour drive I have tried touching the external lines with my hands up by the cooler and they are cold. back in front of the thermostat they are hot. According to the Bentley manual the thermostat should open at 113 degress. My first question is should I be seeing the thermostat open at these tempatures? After an hour of driving my temp gauge is sitting right at or above the first mark.

Second, if I change out the thermostat should I also replace the pressure relief valve? I notice our host no longer offers a replacement of it and without seeing this item I am not sure if it is even an item that can fail.

And lastly should I be concerned about replacing the thermostat and having the old oil that is in the lines and cooler pump back through the engine and contaminate things? Is there a good way to use something line a hand pump once I have the thermostat removed to pump a good amount of oil from the lines and the cooler?

My experience with the external thermostat is this: The opening temperature is more around176-180 degrees. I am not one to question Bentley but I've never heard of the 113 figure as applied to the external stat. As far as your cold oil lines, you would not feel the heat unless the car is above 180 degrees. From your post, it's not clear if your temp gauge or car indicated you were up there. On those times when the gauge gets up to the third mark, that's when you should check the oil line. If you're concerned about the old oil, it is possible to purge the lines if you're going to replace the thermostat if it gives you peace of mind but remember, in a fully functioning system, the old oil still remains in the lines and cooler whenever you change the oil anyway. It does pass through the filter before it returns into the tank.

After an hour of driving with the temp gauge a little below 9 o'clock the lines are still cold to the touch. Hotter then anything before the thermostat. Tried banging with a hammer as I have read some had luck on sticking it with that.

Is there any need to replace the pressure relief valve itself well I am in there or is this not really a failing part and all I need to replace is the spring?