May I ask, how much did Firestone charge to replace your coolant elbow (how many hours labor)? And how long ago? Was this new leak apparent immediately after the elbow was replaced? And was this elbow done before or after your crank sensor replacement?
Unless they took off the entire upper end (UIM/LIM...at least 3-4 hours' labor) or the entire tensioner assembly (I dunno, 1-2 hours' labor?), they would have had to bend-and-wiggle that 90 degree plastic elbow into place, which could easily have cracked it, or dislodged it'* o-rings.
Upon prying the pieces of the old coolant elbow out, it is also possible they gouged the hell out of the aluminum sealing surface in the tensioner (or the LIM), which could cause a leak.
If they did take off the tensioner, it'* possible they didn't hook everything back up to it properly--or that they cracked it themselves.
Whatever the case, you need to pinpoint EXACTLY where that leak is. Meantime, find out exactly how the shop replaced the elbow...if they removed the tensioner, how did they not notice it was cracked then? I smell a potential cover-up...
2004 Buick Lesabre Limited, Gran Touring; Bone Stock
1998 Buick Lesabre Limited, Gran Touring; Mods: Poly sway bushings/endlinks, Tru-Cool trans cooler, Thrasher shift kit (med), PLIM, front PEM; Mods in progress: Alot of stuff, but slowly...