CANNOT Seal Thermostat Housing on 5.0

[bmdubya1198]

4.6 ford v-8 are notorious for leaking coolant under the thermostat. Many youtube on the subject. The leak will appear under the thermostat housing where the aluminum crossover is mounted to the plastic intake manifold (the o-ring seal fails). Unfortunately the aluminum crossover can only be removed when the intake manifold is removed from the engine. I had a small leak for years before I searched youtube and found out how common this oring failure is. I don't know if the 5.0 has similar issues? I had to constantly keep an eye on the coolant level and would occasionally find fluid under the thermostat housing and in the sparkplug well.

I ended up buying an intake on Amazon for about $150.

I'm not sure how common it is except for when there's a misalignment of the thermostat like in my case. I wish there was a rubber o-ring instead of that paper gasket on the 5.0, that would make it SO much easier to prevent leaks.

 

[1998Exp]

4.6 ford v-8 are notorious for leaking coolant under the thermostat. Many youtube on the subject. The leak will appear under the thermostat housing where the aluminum crossover is mounted to the plastic intake manifold (the o-ring seal fails). Unfortunately the aluminum crossover can only be removed when the intake manifold is removed from the engine. I had a small leak for years before I searched youtube and found out how common this oring failure is. I don't know if the 5.0 has similar issues? I had to constantly keep an eye on the coolant level and would occasionally find fluid under the thermostat housing and in the sparkplug well.

I ended up buying an intake on Amazon for about $150.

Not much similarity between the two engines: the thermostat in 5.0L is in a different position, mounted vertically, and the manifold is all metal.
By the way, that aluminum crossover tube in the 4. 6L manifold is an improvement; originally the manifold was all plastic and the crossover cracked in virtually 100% of them. Sometimes that leak was small, but because of the location the spilled coolant often flooded the plugs, causing misfire.

 

[bmdubya1198]

Thermostat is still not leaking, and replacing the heater pipe solved the other leak of course. I wish people didn't mangle those in junkyards while getting the intake manifold, I could only find one in tact in one of the local yards.
I flushed out the system even more today (circulated 10 gallons of water, it's still a little rusty, but MUCH better than before) and vacuum filled it with coolant and distilled water. That was after I ran it for a few days with Blue Devil cooling system flush additive. It seems to have loosened things up a bit, the chunky rust paste in my radiator cleared up quite a bit once I put the hose in there!