[DeTomaso] Overheating problem

[George Sekula]

I am struggling with overheating after I changed the water pump and thermostat.  New water pump is an Edelbrock 8844 with a new overdrive pully.  The thermostat is a Robertshaw 333 from Flowkooler via Summit Racing. I tested the operating temperature on the thermostat several times and it opens at exactly at180F.  The dimensions match their website.  The original bypass restrictor is still installed, with a 3/4" hole; the thermostat plunger is 11/16".  It acts like there is water in the engine that does not get circulated until you shut the engine off.  Hot water violently flows into the overflow tank and the water temperature instantly raises 30F.  When you start the engine everything acts normal.  You can feel the water start to flow in the tube at 180F, radiator warms up, fans turn on and the temperature holds perfect for a while.  Then the temperature slowly climbs.  Driving the car, the temperature will slowly climb higher, maybe 210F. The two radiator fan temperature switches work as they should, but they are not detecting this hot water.  When I filled the system, the bleeder on top of the radiator was open with 3 ft of clear tubing to get it higher than the block and tanks.  The temperature sender in the top of the block was removed until coolant flowed out (wish I had added tubing).  Tried raising the back, then tried raising the front while topping off the tank. The leaking pump that I replaced was a Wieland and it was not drilled for the bypass circuit, the thermostat was a Gates 180 that I installed 30 years ago. Radiator is a 3-pass aluminum with two large pusher fans.  What is the best method for filling the system to prevent trapped air?  Are there other things that I need to check?
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   I am struggling with overheating after I changed the water pump and
   thermostat.  New water pump is an Edelbrock 8844 with a new overdrive
   pully.  The thermostat is a Robertshaw 333 from Flowkooler via Summit
   Racing. I tested the operating temperature on the thermostat several
   times and it opens at exactly at180F.  The dimensions match their
   website.  The original bypass restrictor is still installed, with a
   3/4" hole; the thermostat plunger is 11/16".  It acts like there is
   water in the engine that does not get circulated until you shut the
   engine off.  Hot water violently flows into the overflow tank and the
   water temperature instantly raises 30F.  When you start the engine
   everything acts normal.  You can feel the water start to flow in the
   tube at 180F, radiator warms up, fans turn on and the temperature holds
   perfect for a while.  Then the temperature slowly climbs.  Driving the
   car, the temperature will slowly climb higher, maybe 210F. The two
   radiator fan temperature switches work as they should, but they are not
   detecting this hot water.  When I filled the system, the bleeder on top
   of the radiator was open with 3 ft of clear tubing to get it higher
   than the block and tanks.  The temperature sender in the top of the
   block was removed until coolant flowed out (wish I had added tubing).
   Tried raising the back, then tried raising the front while topping off
   the tank. The leaking pump that I replaced was a Wieland and it was not
   drilled for the bypass circuit, the thermostat was a Gates 180 that I
   installed 30 years ago. Radiator is a 3-pass aluminum with two large
   pusher fans.  What is the best method for filling the system to prevent
   trapped air?  Are there other things that I need to check?