I was wondering if anyone has encountered problems with the headlight washer units. On several occasions the sprayer head has come under such pressure that the little round circle on the side (pressure relief valve?) has blown off and rendered the system unusable. There is a little spring underneath the round cover that must be reinstalled before the cover is snapped back into place. I also recently discovered that the entire sprayer unit can blow right off the assembly. Mine was missing completely after I responded to the check wiper fluid warning. I assume this because I doubt anyone would be inclined to steal one sprayer head. Mercedes sells replacements for $40. My question is do you just shove in the replacement head or is there some specific installation procedure? Any input would be welcome. Thanks, Adam.