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One should have the service manual within reach for electrical diagnosis.

Wow, you've almost had that car as long as I've had my 89 Cutlass! Can't remember if I got mine in late 93 or early 94. Yes, that seal goes bad in all of them. Not if, but when. Rear main seal is rare. Oil pump drive O-rings going bad I'd say is 100% rate. If you were going to DIY it, I'd say don't worry about pulling the rear head. I owned my 94 for 12-years and my fudge-fix lasted for most of that time up to the day I sold the car. If you're having a shop do it, I imagine the intake manifold R&R itself isn't cheap, so I can understand wanting to do the head gaskets at the same time so as not to have to pay for a repeat job in the future. However, head gaskets on a DOHC V-engine sounds like it could be quite expensive labor-wise.

Good day, I have been a W body enthusiast since high school 04. In my student parking lot, we had a 93 Gran prix, 94 olds cutlass supreme, 94 cavalier z24, 95 monte, and my lumina z34. These cars were everywhere! My first car was a 94 lumina z34 (still have it). In 2012 I put a 4.9 PFI in it and it is almost complete. I just need to replace the rear suspension and odds and ends. I have a 99 Monte (needs some work), and I just picked up a decent (needs some work) Cutlass supreme. I am buying a new top for the cutlass on Friday. I want to get black canvass instead of the white (the car has black leather interior). They come in black, grey, white, red. What do you all think would be the best color? Just curious. Very few of these ole buggies still around (at least in my area). I thought I would join the forum to see what you all are up to (I feel very late to the party). I already have seen some super nice examples of these cars (nice job everyone!). Ill post more as spring hits and I can get them out, and work on them more. Also, not adverse to loading them up on the trailer for any meets that might happen. Thank you! Hope you all have a wonderful day!

anyways, welcome to the site.

Thanks all for this. As of the moment the car is in storage do it will be a while before I can check it out, but I will say I get more & more confident this will be the cause. It has been happening for a long time. Form the day I bought this car in Oct., 1994, I always wondered where a quart of oil was going every 1000 miles or so. My money is on this as pictured above, it was probably badly sealed to begin with. And these things don't get better, only worse. I went in and checked my 2020 repair bills from when I had the intake manifold gaskets replaced. The mechanic also replaced the gasket for the part 10130955 as you see in the photo but no mention is made on whether the distributor plug seal was addressed so I am going to assume it was not. While it's a shame all that work that was done to the motor back then would have to be re-done just to get at what needs to be repaired, so be it. Even if I decide to get the rear head pulled to replace the O-ring rather than trying my luck with sealant, that's still way better than having the entire motor pulled. I might as well go the whole 9 yards and have both head gaskets replaced for a one and done job. I should be getting the car out of storage within the next few weeks, I'll keep all posted on how things progress, and thanks again, much appreciated!

You're in the right place because we love our W-bodies here. Welcome!

I've ground the top ridge of the pump drive down slightly to allow for more room to work, then use a distributer gasket for a Lumina van with a 3.1, just give it a cut and slather it in RTV, seems to work well. and I'll be damned if I'm pulling a head just for that.

any '96-03 3400 will drop right in with the 1st gen OBD2 harness. You will have the easiest time with a '97 system (harness and PCM), I'd go with that. A '96 system would work as well (though it's less tunable should you go that route), but with either setup you go with, grab a PCM from a '96-97 Venture/Montana/Silhouette.