Sounds like a classic case of your SLS high pressure hose starting to develop a leak. I've had this happen on all 3 wagons I've owned. It will get to a point fairly soon where it will be pretty obvious where the leak is coming from!
This hose runs from the top of the SLS pump over to a connection point on the right inner fender, under the side of the air cleaner.
Is the fluid level dropping in your SLS reservoir?

__________________
Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John