Dual thermostat housing how to seal?

[bdv]

I am in the process of installing the hi-flow water pump with the dual thermostat housing. My thermostats are GM part number 12559336 on the actual thermostats there is a molded rubber casing acting as a O-ring to seal them against the Water Outlet Outlet housing (12564276). The Housing - Crossover Manifold (12553405) and the Water Outlet Outlet housing (12564276) are mated together with the two thermostats in between and held by four Outlet Bolts (24504922). As far as I have been able to find out from the dealership there is NO gasket between them. My question is do:

I leave it with NO gasket?

Use Anaerobic Gasket Maker (as used on water pump)?

Make gasket from Fel-Pro

[6.5tblack]

I said the same thing when I changed out my thermostats on a 98. NO gasket. The rubber on the thermostats do the sealing. No extra gasket needed. :D

[Craig M]

6.5tBlack is correct, the rubber piece that goes over the lip of the thermostat acts as the seal. I had to go to 3 parts places to get a new seal unit to bolt up my dual thermostat.

[lfytsmith]

I got to do mine twice. Never saw an O ring type gasket before, didn't know that the thermostat slips inside the bugger. For good measure I used permatex blue on the mated surfaces. I put it on as thin and even as my finger could spread it. I put my truck thru its paces last year hauling my 25' Coachman on 90 plus humid days without any trouble.