there are ways to test it, steve has written a note out there on it too. However, i do not have the equipment to test, i just replaced mine it was $100 for my 560 should be less for yours i would hope. A good shop should be able to scope it for you too.
m

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Martin Ingram
Colorado Springs
2005 320 CDI
2006.5 VW Jetta TDI
1991 560SEL (179000 Sold)
1972 280SEL 4.5 ('The Lead Sled' 320000 miles when sold.)
1972 220D (225000 when sold)