I have a '95 SE Bonneville with the 3800 series II engine. I just finished the LIM and UIM replacement and plan to do the valve cover gaskets tomorrow front and rear. Anyways here are my questions, in no order, just random **** I cant seem to find a straight answer to after searching :(

1. The car makes a rattle from the exhaust upon shifting. Is this common? I've read it can be the heat shield. Thoughts?

2. I just had my mechanic replace 4 mounts. 2 engine, 1 transmission, and 1 somewhere else. How many mounts are there for the engine and transmission? NAPA auto parts only had these 4 mounts to sell me but im thinking is there more?

3. I put an aftermarket oil pan on (it looked high quality and was only $50), however it is leaking from the drain plug. It has a metal bushing. Its snug as hell but oil still drips out. Ideas how to rig something up to fix this? Bolt is not same size as OEM unfortunately... Yea I know..dont buy aftermarket...too late! lol

4. Car seems to be leaking in the rear passenger floor area. No coolant smell and mechanic said its not an issue with the car as far as fluids leaking, it is coming from outside in from the elements. Is there a common seal issue in this area? Any idea how to diagnose this?

5. At night the car wont turn the lights on automatically anymore. I know its something to do with the twilight sentinel sensor, however, I cannot find one of these anywhere! Also, is this related to the dome shaped sensor? or the flat sensor both near the windshield?

6. Car has a issue with reading the temperature outside on the Electronic Climate Control unit. How to fix?

7. Lastly, I hope lol, what is a simple and easy way to add a few HP to these cars? Once Im done rebuilding/fixing everything on this car and getting it back to running solid, I wanted to do something simple to add some power or even just help the sound of this amazing engine. I own this car because of this motor I love the 3800 series cars. Please dont say put a L67 in there...Im taking about a cat replacement or a air intake or exhaust swap something simple

Thanks for taking the time to read, I hope to fix all of these issues one by one and then start working on the cosmetic stuff next! New tint, new carpet inside, new headliner/sunshades etc!

Guess you only get 5 mins to edit posts...weird on a car forum...but ok.. I need to add this:

8. When putting the LIM back in after I did the gaskets, I did not follow the torque specs on the twelve bolts, in fact, I didnt even use a torque wrench. I just went around all twelve bolts and tightened them in a staggering random order to just snug, then did a second pass with my hand wrench and tightened them to what I thought was "enough". Is this ok? Car runs amazing after and no signs or coolant leaking anymore. Worth taking it all apart again to get the bolts to the recommended 11ft/lbs? I did try and make sure I tightened every bolt about the same.

Just noticed this thread as I was heading off to bed, I'll see if I can help you when I wake up, unless somebody has already helped you.
It is sometimes easier to have different questions posted in their own threads, as this one could get really cluttered from so many questions, still I'll see how I can help after some sleep.

Yea I figured this might be a little tedious in the way it'* styled but each issue is numbered so hopefully those who are generous enough to help out will just designate with a number what they are helping with and I will await your reply thanks

1. Yes, check the heat shields.

2. There are 4 mounts. 1 is in front of the serpentine belts, another is between the front of the engine and the radiator, another is behind the transmission(drivers side) to cradle and the last one is the dogbone between the transmission(passenger) and cradle.

3. Replace the oil pan with OEM

4. Rear door seals are pulling out at the corner door jam. Sometimes you can reset the seal by pulling most of it out of the car and then reinstalling it.

5-6 I'll have to look in my FSM.

7. A few ponies? Start off with...
A. Cold air intake
B. Front exhaust manifold is restrictive. Change it out for a header.
C. Exhaust downpipe, get a 3" pipe. While your there, get a high flow cat. But good luck depending on the state you are in.
That'* about it for a few extra ponies. Anything else would require bigger costlier bolt on stuff. Like an L36 top swap.

I'm in Florida so it'* all good. Got any links to where I could purchase a good high flow cat, down pipe and header/ CAI for the 95 bonneville?

And thanks I'll check the rear door seals at the jam. The moisture seems to be leaking under the carpet upward but only on the rear passenger side. Kinda weird.

Try zzperformance.com look in the 3800 exhaust and intake section.

Just curious, but did the exhaust make the rattle sound before they replaced the motor mounts, or just afterwards?


As for the water getting in, I have pics of what is in my FSM on tracking water leaks here.
https://www.gmforum.com/buick-172/no...4/#post1617545

Oh yeah, and here is a good video if you need help tracking down the water leak, it is most likely coming from where Mike said, but posting it in case you find more water in the floorboard after fixing the rear door seals.

As for your twilight sentinel, yeah the two little sensors on top the dash near bottom of windshield are the solar sensors.
If it is the switch they are pretty easy to replace, as long as you don't force it when you plug the new one in, doing so can make the harness connector pop back up inside the dash, then you need to carefully use something like needle nose pliers to get it back out and flush with the surface it holds onto.
What type of twilight sentinel switch do you have?
Some have just interior slide switch, and a twilight sentinel slide switch.
Mine has a traction control button at the very bottom of it.

I'll upload what I found for the outer and inner temp sensor.
Granted these are from my 96' Park Ave, I think they may be a bit similar.
Because my twilight sentinel switch lists as a 95', at least the only match I have found for mine lists as that.

Thought of another ok place for parts to add a few HP.
3800 Performance - high performance aftermarket car parts for your Grand Prix, Monte Carlo, Impala, Regal, Bonneville, and V6 F-body!!

Of course there is also INTENSE Racing - Leading Global Supplier of 3800, Ecotec, and LSx Performance Parts , but I don't know how quality his stuff is anymore, used to be good, thing is that is where you get the $$ stuff, and for most of that stuff you'd want a better transmission, and a few things beefed up, as well as a PCM tune.
You may not want to look at what all they have, because I have been drooling over a few items for a while, and if I get this 2006 Grand Prix I am looking at then I may at least get me some nice projector headlamp assemblies from them...
If not one can keep dreaming!