I didn't want to start a new issue as this one seems close to what I have. Please excuse the book as I have been on this for weeks and am getting nowhere but I wanted to try and mention everything that I've observed.
I do not have a sunroof. Initial problem was: When it rained, leaking water onto passenger side front floor and rear floor would flood, mostly on passenger side. Some of that may have entered via rear left door but not sure. Checked plastic (under door panel) on front passenger door and was coming off. Stuck plastic to door with adhesive. Door plastic is now better but could be leaking as I found a very small amount of water (less than a teaspoon) on front passenger floor very close to door in front corner. I have kept the car covered with plastic. I not been able to find any drains that many reference. One person said to left of blower motor on firewall but I can not find any drain. I poked every hole I could find with wire under the car. Can't find any drain. Have mostly dried out floor via vacuum and open windows all day, several times. Problem I am trying to solve: When trying to start, flickering dash lights and clicking. Hard starts. Dash security light is on and has been for several years. Check engine light was on for months. Replaced o2 sensor. I haven't notice it come on recently. Good battery, assume good alternator (12v off, 13.6v maybe more when on), new starter. Clicking and lights flickering intermittenly, when trying to start. Sometimes starts right up, other times have to crank it several times (or jump it). At times, when cranking, hear a noise as if starter problem or something not right, kind of a "clank" under the hood as if something turns as it should but then stops causing clank noise. Kind of a heat shield thin metal sounding clank. Repeated tries to start, it sometimes starts after 5 or 6 tries or sometimes it starts immediately like there is no problem.
checked tension on serpentine belt. belt seems ok but not sure. Pulled on it, turned pulleys a little.
I am unable to turn belt tensioner bolt at all. Turned alternator fins a little bit by hand. Seemed like belt could be tighter but went back to start car, no lights, no flickering, no nothing. Acted dead. More general poking around under hood. Not really doing anything (pulling on belt etc, turning alternator fins again etc). Go back to start and it either starts or get flickering lights, hard start again sometimes with clank noise. Tightened battery bolts, seems better, started but I bet that when I go out and try again later, there will be hard start again. Had codes earlier, one indicated o2 sensor and as stated earlier, replaced o2 sensor. Seems check engine light may be solved. Using scanner requires turning key on but not started. Several times when I tried that to get codes again, sometimes easy start sometimes hard start. Seems everything intermittent (I cleared codes earlier). Now I can't get any. Previously I had codes P0135 (o2sensor I believe) P0440, P1655. After o2 sensor replaced I cleared codes. Last code I had was only one and that was P1655. Just checked water on front passenger floor. Again very little water but there is a large black conduit full of wires, must be 10 or 15, those are wet inside the large black conduit.

Ummmm . . .

First things first:

Year: 1996?

Color: Black?

Make: Cadillac?

Model?

Odometer?

How many miles have you owned it?

How long have you owned it?

Any damage/accidents/etc.?

Does it still leak when it is covered with the plastic you mentioned?

Wow. almost unbelievable I would leave that out. 1996 Pontiac Bonneville SSE 3800 motor, 136K. All options except sunroof. I've driven it 60K or so miles. It has been covered and found that very small amount of water in the conduit today.

. . . ?

*moved to 1992-1999 section*

It would have to be parked at a pretty severe angle for a leak on the left-rear door to flood the right side carpet (assuming with no wet/flooded carpet on the left side as it is not mentioned here).

I may be speaking misguidedly here, but I have several cars' worth of door plastic that isn't completely glued in, usually because I've opened the door up to fix something. None of them (including your Bonneville'* 1997 LeSabre cousin) has this issue no matter how much rain comes down. They've been through every kind of rain there is; little bitty stingin' rain, big ol' fat rain, rain that flew in sideways, rain that comes straight up from underneath, and even rain at night.

Is this an improvement over pre-door-plastic-repair amounts relative to the amount of rain received?

I'm not familiar with the blower-motor drain. There is a path for air-conditioning condensate to drain to the ground behind the right-front tire. Perhaps that is what many are referring to?

Either way, have you checked door seals to make sure they are in place and completely glued/clipped/bolted/etc. in place?

Also, have you had a windshield replaced recently? . . . or ever? If so, when was this done?

Does starter turn engine over but it never fires?

. . . or starts firing but has a hard time coming up to idle?

Or, does it click and not turn the engine over? . . . or same plus dash lights go out?

Did the <Check Engine> light have a code behind it for a bad oxygen sensor? . . . or did you replace the oxygen sensor on a hunch?

Did the <Check Engine> light come on after the oxygen sensor was replaced and before "recently" ?

"Good" like 12.x volts showing with engine off and/or "Good" like it is fairly new and/or "Good" like it is a quality brand/model/etc. and/or . . . ?

If not answered already, how old is the battery?

Yup this is good.

Are the battery'* terminals clean and tight, like you've checked them during this problem and wire-brushed them recently?

From Napa or Autozone or first-from-China or . . . ?

What was the problem with the previous starter?

This makes me re-wonder about the condition of the battery and the cleanliness and tightness of the terminals.

Does the starter turn the engine over each time you crank it several times?

This is interesting. Jumping is done for a dead or low battery, as in battery not supplying necessary voltage and amperage to start vehicle. This tells me three possible different things:

1. Battery is bad, possibly showing proper voltage but unable to supply enough amperage to start car.
2. You are using the starter so much during a start attempt that you are draining the battery. I can tell you for certain that it takes an abusive amount of turning the engine over with the starter to get a battery to this point with this driveline.
3. One or both terminals are loose or corroded, and jump-starting "solves" this issue by bypassing the terminals or moving them a little so they make better contact.

Weird. Open hood and have somebody else crank it. See if you can localize your noise.

How is your catalytic converter doing?

How many miles on the odometer?

So . . . tension is okay?

How about condition?

How old is the belt in years and miles?

Either way, this is not your starting problem.

Like, to release tension? Have you tried both directions?

Still don't think this is directly related to starting issues.

This makes me re-re-wonder about the condition of the battery and the cleanliness and tightness of the terminals.

Thinking this is the starter engaging to turn engine over, then losing power briefly (therefore retracting the pinion gear), then regaining power and jamming the pinion gear into the flex plate improperly, possibly while the flex plate is still turning from momentum.

This makes me re-re-re-wonder about the condition of the battery and the cleanliness and tightness of the terminals.

Good.

Good.

Let us know. For now I'm going with "seems better, started"

Cool, possibly answered my question from earlier, however, it'* so far up the thread that I'm not going to take it out.

P0135: Yes Bank 1 Sensor 1 Oxygen Sensor bad heating circuit, good you replaced it, not related to your starting problem
P0440: Evap system leak, not related to your starting problem
P1655: Evap purge solenoid control circuit problem, not related to your starting problem

As long as there are no breaks in the insulation on the wires, this wouldn't be an issue.


CahtedralCub'* guess/summary for the leak: Check door seals.

CathedralCub'* guess/summary for the starting issue: Check for buildup and/or corrosion on the battery terminals.

Took the 18 month old $147 battery to the store and they confirmed it'* bad. They'll have another new one for me tomorrow. I am hoping that is the only problem but I am doubtful. Thanks for the questions and I will update soon after.

What store was it from?

NAPA store close to me

Some of the info/questions above are now moot so starting from => Car now starts. New battery is installed along with (probably not needed) new starter mentioned earlier. I could get very detailed as to how car was parked at different times and where water was but would make for boring reading. As of now, It'* been on ramps for about a week. Roof mostly covered with plastic tarp but not on the left front side, perhaps not on the right front side either but not sure. Tarp did not reach the back of the hood near where meets windshield even though I had an old ratty car cover over the tarp that covered the whole car. Today very obvious water entering front driver floor area and to back left floor, Some but much less less, also on the right rear floor. Again, front wheels on ramps. The rubber/plastic molding around rear doors opening has shrunk but I've only seen droplets in that area before on the left rear.