Hi everyone - new member to the forum, and I was drawn here by this thread. I have been using my HR freeze dryer for a few months now and it's been great. Reading about all your experiences shows that I'm not alone in loving this machine! . Lately, my machine has decided to be a pain. Wasn't drawing enough vacuum to cycle. Flush pump, clean out pump, and all that goodness, but still no luck. Have been working with HR to figure out what's going on, and they've been very responsive, so kudos to them. Still chasing the problem, however, so I thought I would ask the assembled experts here. A bit of background on me - I used to work in a sold state fabrication lab (university research lab) and had a lot of hands-on work with ultra-high vacuum equipment. The pumping we do for freeze drying was what was required to just start the "real" vacuum pumps on those machines, with ultimate vacuum levels a few more demial places over. I've chased many a leak in my time,but it was: A. Long ago. and B. I don't have the test equipment I did then. I guess what I'm saying is don't be afraid to get too technical with me in your answers. What I wouldn't give for a helium leak detector right now... OK, so what have I done thus far? Flush pumpClean pump interior and re-seat gasketFill with clean oilRun full system test with no food in chamber (results, 630 mTorr lowest steady reading - looking through the oil level window, some bubbling seen in oil even after an hour of pumpdown - some "air" noises from pump)Isolated pump by capping the stack (no meter to measure pressure, but no bubbling after a very short pumpdown - pump sounded normal for a high vacuum situation)Reinstalled the vacuum hose and capped far end of hose to do a hose test. (same results as pump alone)Reattached hose and ran another full system test (results, 750 mTorr lowest steady reading - looking through the oil level window, some bubbling seen in oil even after an hour of pumpdown - some "air" noises from pump)Upon turning off the pump (no isolation valve on the pump - standard setup), the chamber pressure rose quite rapidly going to 2000 mTorr and continuing up in a couple of minutes or so.Observations: Oil has remained clean and clear throughout testing, so it looks like it's well flushed.When isolated, the pump seems to behave well. Short of putting a meter on the pump, my impression is that it is operating properly. I'm considering investing in a good meter to verify that it is reaching a good ultimate vacuum.The hose appears to be OK, and by implication, the gaskets at the connections are working as well.The bubbling of the oil even after long pumpdown indicates a leak somewhere in the system.The differing vacuum levels during the system tests would be consistent with either a door seal leak or an drain valve leak.Wherever the leak is, the pump is unable to keep up.Door seal appears good against the plexiglass side, even stripe of contact, nice and wide. Inside gasket groove has been checked for debris and cracks. Looks OK, but the design seems odd to me!That's what I have so far. Thoughts?