Replaced a LIM (and upper LIM) on a 2005 Pontiac Bonneville 3.8l last weekend. A pretty easy job, but time consuming. Having a heated garage was a huge help. One benefit of working outside is the lighting can be better than in a homeowners garage.

What did not go well:
Lost a bolt that holds the plenum to the manifold. This is a special item and had to drive 80 miles to a dealer that had one. I take great care to label and store every bolt, nut, etc- no idea where this ended up

Did not hook up two fuel lines connecting to the rail. Looked hard but did not see they were on top but not pushed in. Turned the key to on position but did not start the Bonneville, did an inspection and smelled a bit of fuel. Turned everything off and searched and saw the problem. Should of had a fire extinguisher nearby.

What went well-
Bought a belt tensioner as a spare when I bought the gaskets- huge win as the prior owner gasketed the plastic elbow into the old tensioner, making removing the old elbow parts and gasket material near impossible.

Used the "copper" permatex gasket maker. Stuff is awesome.

Replaced the plugs and plug wires- great time to get the rear plugs with plenum out of the way

Had a vacuum nearby to quickly suck up any materials trying to enter engine with manifold removed

Endstate- took about 45 seconds to start, not sure if it was fuel trying to get to the injectors or what, and ran rough for about two minutes. After that, ran awesome, went on a 40 mile test drive at 10 degrees Fahrenheit and zero issues.

Checked coolant level twelve hours later and no visible leaks or loss.

A few more notes, Mike mentions in some of his posts about lubing the o-rings, I did this with plumbers high temperature grease on rings that were used around coolant, and oil for o-rings used around fuel.

I am sure I torqued the LIM bolts much more than GM directs. The GM LIM torques seemed way to loose- I decided to crank it down more and more, knowing the FELPRO modified LIM gaskets have metal grommets where the bolts feed through. I think it will be ok.

I replaced the coolant holding tank- old one was very dirty inside, having cleaned on before- it is better to replace with new than try to clean a tank that is dirty inside. New tank only $9 at RockAuto.

Also replaced the thermostat, and thermostat housing, along with serpentine belt. Finally, saw the fuel injector wires on cylinder four with cuts in the insulation- I am sure they will soon fail. Put some teflon tape on the cuts and will go back later and formally protect.

A good experience, glad I did it. Considered sending it to a shop due to time constraints, very glad I did it myself, knowing exactly what was done, proper cleanup of surfaces prior to reassembles, and simply I may care more than a
mechanic getting paid by the job and trying to make the repair profitable.

Good work! Got any photos?
I have had no problems with mine since doing the upper & Lower.
I used the metal elbows and no leaks again.
Those rear spark plugs are no fun, I installed new Iridium while I had it all apart too.

Fun job eh?
It was not hard, but time consuming for sure, it took me longer because I got my dremel and polished my fuel rail, and my thermostat housing, then I measured 1.9" x.9" for my LIM'* runners, and I grinded them all to be the right spec size. I also knocked off a lot of the rough inside of each runner, but I did not want to polish it, you still want a bit of turbulence going on from what I understand, although you'd think totally polished would be best..
I tightened my bolts all to spec, and have had no issues, I think the aluminum framed gasket can handle a tad higher torque, hopefully you did not go too tight though, and luckily no bolts broke off on you.
I slightly over tightened a coolant water bypass cover bolt, the cover on the side of the LIM, and it broke easily.
Been around 3 years now with no issues, I just wish the aluminum elbows were out when I did my UIM/LIM< they came out right afterwards.

Art,

I will post some before and after pics- I did not take step by step pics but think the pics I did may be of some benefit to someone in some manner.

William, you should be a classic car restorer- no detail left behind.

Never thought to polish the fuel rails- but did replace the thermostat housing with a new one as a preventative act. I also planned on replacing the radiator, but decided to send it back to RockAuto and get the $150 refund (bought a GM OEM radiator).

I'd love to do something like that, I have always had an eye for detail, and I can tell when anything is slightly off, or not the same as whatever else it may be a part of.
What prompted me to polish the fuel ail was that the rear part of it in the rear got stained from the small gas leak I had from a bad o ring.
Glad I noticed that, and fixed that issue.

Worst case scenarios I have faced with an upper plenum leak at the EGR opening.....

Engine becomes hydro locked.......when that happens, I change the oil twice, after the parts are installed, and cross my fingers....one job I did, car was fine....two weeks later, the connecting rod went through the side of the block....another one, car came back with a bad lifter noise.....basically, did job again, replacing the lifters......customer was not happy.......

In some cases, repeated attempts to start the vehicle have snapped off the nose of the starter(white metal).....

And sometimes, so much coolant has found it'* way into the exhaust, that the car won't start....You double check all your work, and eventually figure it out....... I had to jack the front of the car up, to let the coolant drain out of the exhaust.....then she fired right up......first time, it took me almost an hour to figure this out(what the hell did I do wrong?).....the second time, 10 seconds....

Good info Tech II, especially to much coolant in the exhaust- never thought of that causing a no start issue.

Good info here. Even if some of it was a learning experience. Others will learn from it also.

Torq specs are based on the thread pitch, the type of material the bolts are made from and the size of the bolt and the material its going into. Obviously one isn't going to torq a grade 8 M20 bolt with .5 pitch to 500 ft lbs going directly into aluminum.

In a heat/cold environment, its possible one could snap bolt heads off in the lower manifold just because of thermal expansion of aluminum. Something has to give.