New member here with question regarding daughter'* car. 1999 Grand Prix w/1997 Olds 88 3.8l engine. She is single mom who bought this car from tote the note lot and it'* leaking oil from the missing plug pictured. I don't know what is supposed to go here. You can see the reflection of the oil at the opening in question. Sorry for the pic quality but if you right click on it and enlarge it is easier to see the opening. Thanks, any info would be appreciated.

Also, the car keeps running rough and check engine light is on. It threw codes P0300, P0174, and P0440. I have changed plugs and wires, plugged vacume leak, and replaced a coil. Car will run ok for a few minutes and then start to stall with the tach going to zero. It will then turn over but not start. After waiting a few minutes it will start again and go through the same process. I'm thinking it needs a crankshaft position sensor. There is so much wrong with this car it'* hard to know where to start. Got to try to fix as much as I can for her as she can't afford to spend a lot of money on it. I'm afraid the car lot saw her coming.

unfortunately thats a common sight for 3800 owners, the intake is leaking and dripping down the wires.and the lower intake gaskets are leaking coolant into the engine, the evap code is not likely related but i would just do the lower and upper intake then see where you are at. fortunately so many have done it there are a ton of write up here how to do it were to get the parts and what to get. i have had my car long enough its been done twice but the first time i did it all they had was oem type stuff. the stuff they have now wont likely need replaced again if you take your time and do the things i did in my write up.

https://www.gmforum.com/mechanical-1...2005-a-304071/

https://www.gmforum.com/mechanical-1...ts-l36-297702/
some good info on where to get stuff but make sure you put your car in at rock auto because not sure if a gp is the same as impala

https://www.gmforum.com/general-gm-c...279335/page10/

Thanks for the info and link to your write up. I suspected the LIM/UIM gaskets would need replacing and your excellent writeup should help. Aside from these issues, there is a threaded port in the pic that is missing a plug or something. It'* really hard to see in the pic unless you blow it up. It'* where that tiny white spec is in the pic (white speck is actually reflection on oil in the opening). Looks like there should be an elbow or something there. I'll try to post a better pic in a few minutes.

Here are some better pics of the open port in question. Anyone know what goes here? The car is a 1999 Grand Prix, 3.8l non-turbo but I believe it has a 1997 3.8l from an Olds 88. Thanks in advance for any info.

I second the UIM/LIM Gasket needing to be replaced.
I also recommend not driving the car anymore until this is fixed, if enough coolant gets into the cylinders it could cost you a motor, liquid does not compress like air, it can possibly cause catastrophic engine failure.


I'll look at my motor tomorrow and see if I have that same hole, if I had to guess I'd say it was used for holding the engine block while it was being made in the factory, but it does have threads, so I am probably wrong.
The oil that is leaking is most likely coming from the LIM Gaskets like Justin said, I had the same leak from them until I replaced mine.

While you are doing the UIM/LIM, if possible try to change that serpentine belt, it is pretty cracked, and will most likely not hold up too much longer.


Back when I did my UIM/LIM I had never done one before, so I started a thread, it is not a how to like Justin'* thread, so stick to that when doing the repairs.

Reading it may help you with any possible questions that could come up with, I am pretty sure I asked them all, and I got some great answers, I will warn you it is quite long, about 26 pages, but there are some good tips throughout the thread.

Replacing UIM, UIM Gasket, and LIM Gasket. - 3800Pro.com Forum

Thanks for the info WilliamE. Your thread looks like it has a lot of good info.

I wondered if the hole in question was a blind hole for a bracket, etc. but I checked by inserting an ink pen in it and never touched the end so I don't think it is a mounting point for something.

If you are talking about this hole here...



Then you are missing the coolant elbow pictured next to it. And it shouldn't be oil coming out, it should be coolant.

I don't believe that is the hole he is talking about Mike, the hole I am pretty sure he is talking about is the one I've circled in this pic, if so then it is a bit lower and to the left of the coolant elbow, it is also threaded, the coolant elbow bores are not threaded.
It looks like it is a part of the block, and not the LIM.

Oh, my bad. 430 in the morning and I'm still on my first cup of coffee.