No real secret. Lift the headrest to its upper most slide position. Press on the black button, pretty hard and pull the headrest up and out. You may have to slightly lower the hearest as you push on the button. There is a clip type assembly holding the rod in postition. If you have done this and can not get the headrest out then you may have a broken unit. I do find it unlikely that all three would have broken. NOW WE ARE talkiing about the center seat headrests in a wagon??
Operating the center seat headrests is identical to the front seat headrests except the button in exposed and black.
If they are broken then you may have to remove the seat backing to access the mechanism that locks the rods in.


Dave

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1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car