Does my thermostat need an O ring?

I'm repairing the thermostat assembly in my 90, 5.8 bronco. The old thermostat is a 195 Fahrenheit model, and seems to be in working order (did the boiling test). I've got a new housing, and after some careful sanding and dremeling, I've got it in acceptable shape.

Now I'm ready to put it back together. However, I'm working with a buddy who thinks that there should be a o ring between the thermostat and the thermostat inlet to keep the thermostat from rattling around in the aprox 1/64 inch deadspace between t-stat housing and t-stat inlet.

I, in my devil-may-care fashion, am of the opinion to use some permatex thermostat silicone to hold the thermostat onto the t-stat housing during installation, which, IMHO, should reduce the wiggle room to a minimum.

Anyway, tl:dr: does my thermostat need an o-ring?

no there is no need for an o-ring it will not move around once the housing is bolted to the intake. The gasket/silicone is all that is needed.

It just seems like there is a little wiggle room between the thermostat and the gasket that could let fluid thru. Never repaired this part on my bronco before, so I wasn't sure.

yes there is a tiny space there typically not enough to allow any movement. My 1990 351 also has a slight recess there but there is no o-ring ever been in these thermostats.

yo Seedpress,

As Elmo advised.

btw, in the event anyone in the hood says the Ford T'stats have an O ring, they are correct, BUT it is inly for Diesel Engine t'stats.

This is by Ford;

Removal

1.Drain the radiator so that the coolant level is below the water thermostat. Refer to Cooling System Draining, Filling and Bleeding in the Cleaning and Inspection portion of this section.

2.Disconnect the bypass hose at the water pump (8501) and water hose connection.

3.Remove the bypass tube.

4.Remove the water hose connection attaching bolts.

5.Bend the upper radiator hose (8260) upward and remove the water thermostat and water hose connection gasket (8255).

Installation

1.Clean the water outlet water hose connection gasket surfaces. Coat a new water hose connection gasket with Perfect Seal Sealing Compound B5A-19554-A or D7AZ-19554-BA or equivalent meeting Ford specifications ESR-M18P2-A or ESE-M4G115-A.

2.Position the water hose connection gasket on the intake manifold or cylinder head opening.

3.Install the water thermostat in the intake manifold opening with the copper pellet or element toward the engine (6007) and the thermostat ****** positioned in the recess. If the water thermostat is improperly installed, it will cause a ******** flow of coolant.

4.Position the water hose connection against the intake manifold (9424) and install attaching bolts. If a 7.5L engine, tighten bolts to 32-37 Nm (23-38 lb-ft). For all other engines, tighten bolts to 16-24 Nm (12-18 lb-ft).

5.Install the water bypass line and tighten hose connections.

6.Fill and bleed the cooling system