I've searched through here for a good part of two hours and can't find a definitive answer.
My '96 Bonneville Non-Supercharged 3.8 is leaking coolant from an elbow on the passenger side-top of the engine, directly above the water pump. This elbow goes from the manifold (upper or lower?) directly into an aluminum piece that feeds the heater core. It looks as though this aluminum piece shares bolts with the water pump? What is the easiest way to fix this? Do I need to remove the manifold or the water pump? Where to get the right parts?

Common problem here. That is your coolant bypass hose fitting that goes into the lower intake manifold and they all deteriorate and leak. I actually didn't change mine because it broke while I was away and the wife brought it in to get it fixed. I do recall that is was not expensive at all though. Sorry but I can't tell you exactly how to get it out though off hand but I am certain that most people here have done this repair already.

Thanks, I just hope it'* easy to change. I'll have a look at it again tonight. Took me about 3 1/2 hours yesterday just to trace the leak from the bottom of the PS pump! Had to pull off the PS pump and alternator, but now that we're "intimate" it shouldn't take too long to figure out what to do. Anyone swapped this out?

I was under the impression that some of those elbows were plastic (I thought mine was). Make sure it'* replaced with a metal one.

The bypass fitting itself is only clamped in with a single bolt. You should be able to get to it fairly easily on a non-supercharged model by removing the alternator.

One bolt? Geez, I must have been tired! I was thinking it was sharing bolts with the water pump. I'll check it out and snap some pics tonight...also, how is the elbow fitted into the bypass fitting? From what I've read it'* threaded into the intake...

Okay, pulled the ALT off and there were two bolts on the heater - cooling bypass unit and it pulled straight out. The elbow pulls straight out of both holes and does NOT appear to be threaded. It does have an o-ring on each end and they are different sizes. The stupid plastic elbow snapped in half (as I previously read about) and some small chunks ended up IN the lower intake. We'll see where THOSE end up because I'm not pulling that off now! I successfully scraped all the chunks out of the bypass unit (this thing was SUPER brittle, crumbled in my hands) and I'm ready for the new part. I was unsuccessful in locating it at Checker or Auto Zone, so it'* off to the dealer tomorrow. The guy on the phone said they keep ten in stock at all times! Hopefully he has the metal one. I'll post pics tomorrow.

So the plastic bypass fitting broke off into the lower intake... something like this?
http://jlg.net/photos/bonneville/bypass_fitting.jpg

The flexible, twisted bypass hose that runs from the water pump to the lower intake is $3 at Autozone. As you found out, the threaded fitting is a dealer item. The replacement part will be metal not plastic.

You can try using a wet/dry vac to suck the chunks of plastic out of the lower intake. I kind of gave my lower intake an enema using water and a turkey baster, then I sucked the bits out with a shop-vac. Then I drained my coolant and refilled. Then I took the car to the shop to have the coolant properly flushed.

On my 93 SE I replaced the O-ring where the metal heater pipe goes into the lower intake. It was a standard O-ring available at Home Depot... I want to say it was a #53 but I'm not sure.

That comes out? son of a....

BTW, you can pull the upper rad hose at the rad, bend it up and fill with garden hose. That'* how I got the peices of rubber from my deteriorated lower rad hose out of the engine.

Hi Beafraid8 did you pick up that elbow yet? I sure hope there is a brass replacement for the 3800 II coolant elbow.