I have a Lennox high efficiency gas furnace (Model: G26Q3/4). Water is logging in the inducer housing, even after all the pipes, vents, reservoirs were drained. After cleaning, the repairman ran the furnace. For the first 15 min, it works beautifully, then you can start hearing the bearings and the water sloshing in the inducer housing. The condensation is collecting in the reservoir but refuses to drain. As soon as the furnace is turned off, the water drains from the reservoir.I still have water in the inducer housing. Head scratcher for the repair guy.

The PVC out of the reservoir is designed to relieve pressure (4" tube). All hoses were checked for blockage, and found non. You can see steam come out of the outside vent when the furnace ran for 15 min.

What could be causing this? Back pressure but where? Any help would be much appreciated.