There are two types of armrests used on front seats of Vanagons. The earlier type which is nit adjustable is the sort that you described in your Bentley manual. Second type is commonly found on 1987-later models. Sound like the ones you have.

They are held in place on the pivots by a roll pin. The pivots are attached to seat frame with two Allen head screws. Replacement screws are usually Phillips head. If the pivots are just loose, you can often tighten them by pushing the upholstery away and reaching the screw heads with a needlenose pliers and slowly tightening them. 

If that fails or if the screws have come out all the way, then you will need to get a drift punch to push the roll pin out. The armrest will slide out after you've done that. It will then be obvious what needs to be done.

Regards,

BenT

sent from my electronic leash

On Mar 4, 2011, at 11:34 PM, KK AL <kkalnsf@GMAIL.COM> wrote:

> We have an 87 Syncro. The armrests are loosening up. According to the Bently
> shop manual there are caps on the sides of the armrests that pop off for
> access to the mechanism.
> There are no such caps and no obvious way to access the mechanism to tighten
> them.
> 
> There must be something we are missing because we have had them tightened up
> in the past by our local VW mechanic.
> 
> Thank you in advance for any help.