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Discussion Starter #1
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?
 

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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, once bolted in with a proper gasket the thermostat should be snugly held in place. Why would you modify a new thermostat housing?
 

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Discussion Starter #3
Well, the finish was pretty bad on the mating surface of the housing, and there was some light pitting on the intake surface.

In terms of the o ring, it just seems like there is a little wiggle room between the thermostat and the gasket.
 

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Roller rockers are gay
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All T-stats that are not used with an O-ring design move around a little until you put the gasket/housing on. Don't over-think it.

Now, I'd have brought that housing right back to a parts house and ask for another one. you shouldn't have to dremel the fawker to make it work. I'd also throw a new Stant t-stat in it right now. They are 5 bucks dude. You KNOW that stat is gonna fail now. Unless you replaced it within the last year yourself.
 

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All T-stats that are not used with an O-ring design move around a little until you put the gasket/housing on. Don't over-think it.

Now, I'd have brought that housing right back to a parts house and ask for another one. you shouldn't have to dremel the fawker to make it work. I'd also throw a new Stant t-stat in it right now. They are 5 bucks dude. You KNOW that stat is gonna fail now. Unless you replaced it within the last year yourself.
What he said.
Technically the thermostats are around $12 but still cheap.
 

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

This is by Ford for a 96 bronco, but similar to your 90;
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 flange positioned in the recess. If the water thermostat is improperly installed, it will cause a retarded 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
 

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Roller rockers are gay
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What he said.
Technically the thermostats are around $12 but still cheap.
The cheap line of Stants at advance are around $5. The lifetimes run between 8-10 typically.

If you replace the stat, do NOT get a "fail-safe" stat. They blow ass. Trust me, I've watched a lot of guys replace them every 3 months on this site.
 

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The cheap line of Stants at advance are around $5. The lifetimes run between 8-10 typically.

If you replace the stat, do NOT get a "fail-safe" stat. They blow ass. Trust me, I've watched a lot of guys replace them every 3 months on this site.
Is "fail-safe" a brand, or a specific type of t-stat?
 

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Roller rockers are gay
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I think it's a brand. I don't shop at places that sell it. I stick to carquest and advance auto (I work for the latter which owns the former).
 
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