An injection molding manifold system, comprising: a manifold to receive melt from a melt source and distribute the melt to one or more outlets; an injection nozzle to receive melt from an outlet of the manifold and deliver the melt to a mold cavity; and a nozzle retention mechanism coupling the injection nozzle to the manifold, the nozzle retention mechanism constructed and arranged to apply first and second loads between the injection nozzle and the manifold, the first load being sufficient to maintain the injection nozzle in position on the manifold for installation of the manifold system, the second load being greater than the first load to create suitable sealing contact between the injection nozzle and the manifold upon installation of the manifold system; the nozzle retention mechanism comprising: a retainer constructed and arranged to retain the injection nozzle to the manifold with the injection nozzle extending from the manifold in a longitudinal direction; at least one mounting clip to mount the retainer to the manifold, the mounting clip constructed and arranged to permit linear movement of the retainer relative to the manifold in the longitudinal direction; and at least one spring to create a variable load between the injection nozzle and the manifold when the retainer is mounted to the manifold, wherein the spring creates the first load when the retainer is in a first position relative to the manifold and creates the second load that is greater than the first load when the retainer is in a second position relative to the manifold, and wherein in the second position the retainer is moved out of engagement with the mounting clip and is moved against the manifold. a manifold to receive melt from a melt source and distribute the melt to one or more outlets; an injection nozzle to receive melt from an outlet of the manifold and deliver the melt to a mold cavity; and a nozzle retention mechanism coupling the injection nozzle to the manifold, the nozzle retention mechanism constructed and arranged to apply first and second loads between the injection nozzle and the manifold, the first load being sufficient to maintain the injection nozzle in position on the manifold for installation of the manifold system, the second load being greater than the first load to create suitable sealing contact between the injection nozzle and the manifold upon installation of the manifold system; the nozzle retention mechanism comprising: a retainer constructed and arranged to retain the injection nozzle to the manifold with the injection nozzle extending from the manifold in a longitudinal direction; at least one mounting clip to mount the retainer to the manifold, the mounting clip constructed and arranged to permit linear movement of the retainer relative to the manifold in the longitudinal direction; and at least one spring to create a variable load between the injection nozzle and the manifold when the retainer is mounted to the manifold, wherein the spring creates the first load when the retainer is in a first position relative to the manifold and creates the second load that is greater than the first load when the retainer is in a second position relative to the manifold, and wherein in the second position the retainer is moved out of engagement with the mounting clip and is moved against the manifold. a retainer constructed and arranged to retain the injection nozzle to the manifold with the injection nozzle extending from the manifold in a longitudinal direction; at least one mounting clip to mount the retainer to the manifold, the mounting clip constructed and arranged to permit linear movement of the retainer relative to the manifold in the longitudinal direction; and at least one spring to create a variable load between the injection nozzle and the manifold when the retainer is mounted to the manifold, wherein the spring creates the first load when the retainer is in a first position relative to the manifold and creates the second load that is greater than the first load when the retainer is in a second position relative to the manifold, and wherein in the second position the retainer is moved out of engagement with the mounting clip and is moved against the manifold.