2000 cadillac deville
I have a 2000 deville water pump tensioner went
out and broke belt car overheatet replaced both car
still over heating no leaks could it be the
thermostat car never overheated before
Should have a trusted shop look at this, it is possible the heads may have warped causing a bad head gasket. But always check the least expensive part so ya, I would try the thermostat first. Also a compression test would indicate if a head gasket is blown. And it could be as simple as purging the cooling system from air.
Check to see if your water pump is really pushing water. It might not leak but it may not be circulating your coolant.
what is replaced both? did you replace the water pump and the tensioner?... once you overheat a cad it never really runs right again..
also...if you have a doubt in your mind about a block thermostat that is less than 5 bucks why not change out cheapest parts first?