I used to have one of those Topsider units, but changing hot and often contributed to its demise. It collapsed one day.
I experienced an occasional failure of the gasket under the inlet screw on cap. If you pump to much of a vacuum, or the gasket is wet with oil, you can suck it right into the can. I had to take the connection off, reposition the gasket (a flat rubber washer kind of device) and tighten up the connections.
Hope this helps and good luck, Jim
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)