I have coolant getting into cylinders 1&3. Is it the manifold? on 2001 Ford F-150

Had the holes blown out and new plugs installed. Mechanic could not find a "trail" leading to the plugs externally. Truck ran fine for about 20 min. (Note: I was pulling a 22' travel trailer) then the problem came back. Misfiring and running rough between 1000-2000 RPM.

Asked by for the 2001 Ford F-150
Howdy. It is pretty unlikely it is an intake manifold and/or gasket if you are actually blowing spark plugs out of the cylinder head. Are you going through coolant on a pretty regular basis? I suspect you have a head gasket issue. I would recommend getting the vehicle diagnosed before performing any teardown of the engine. Typically, based on your decription we would perform a block test which checks for hydrocarbons (exhaust gasses) in the cooling system. If hydrocarbons are present, you have a cylinder head and/or gasket issue. It may be something else but this is where we would start. Hopefully that helps!
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it could be your head gaskets blown and coolant is getting into your block and pistons like that. mechanic shoulve checked that