OIL LEAK - 1994 Cutlass LQ1

[bluecalais79]

It's that time. The oil leak in the rear main seal of my 1994 Cutlass Supreme SL with the 3.4L motor has gotten so bad that it needs to come out for repairs. In addition to this being in need of replacement, I am going to have the oil pan gasket replaced as well, along with the 3 coils and the alternator while the motor is out of the car. In addition to that, is there anything else anyone can think of that should be replaced while the motor is out, as this would be a golden opportunity to get it done. The engine compartment will also be degreased to clean up the big mess this leak has been making.

It does not need a timing belt, water pump, or any intake manifold work as this was all done 5 years and 10,000 miles ago and no issues here. 

 

Edited January 3 by bluecalais79

[Psych0matt]

I should check my timing belt again, its been a while. I know it has lower miles-ish on it, but I've owned it for 15 years now. My list for this spring is a new starter (gets heat soaked and doesn't wanna crank), and a new window regulator for the drivers side, and while in the door I may clean out or replace the power lock motors, not sure if they're weak or just old and gummed up

 

Doesn't answer your question but it got me thinking haha

[bluecalais79]

Good call on that timing belt, over time they suffer age cracks; 15 years is a long time. 

[GnatGoSplat]

You probably already checked, but make sure it's not the distributor plug seal before tearing into it.  That can mimic a rear main seal leak.

[bluecalais79]

This is an excellent point, can you pinpoint and/or provide a photo as to where this is? For the life of me I can't find it and/or provide the page on the 1994 W Book that may provide a diagram where it is located? I would really prefer not to pull the motor if that can be avoided. Thanks for this memo, much appreciated

[GnatGoSplat]

It's in the valley right by where the transmission and engine block are joined together.  Oil will pool around the distributor plug (also called "oil pump drive") and run down the side right where the transmission mates to the block so where it drips on the ground looks very much like a rear main seal.  An O-ring goes bad on it allowing it to leak.  Shine a flashlight down there, and if there's oil pooled in that area, that's your culprit.  Unfortunately, yes, it's blocked by the rear head.  What most people do is lift it up as high as possible and clean it and the block as well as possible.  Some sandwich a thin O-ring under it, others RTV it.  My memory is hazy, but I think I may have done both.  On my pic, high pressure oil-resistant RTV is the stuff kind of squishing out from under it.  It's dirty because this was many years later, but it worked great.  Official GM procedure is to pull the rear head, but that's way, way too much trouble.

Edited yesterday at 03:25 AM by GnatGoSplat

[White93z34]

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.

[Bake82]

If you need to pull the engine, I may consider the following:

 

 

- the block mounted crank position sensor. 

• They often get stuck in the block and break.  You either need to drill and put a screw in them to pull it out or they break too bad and you need to push it into the oil pan and hope it doesn't cause issues or pull the pan.  

- Steering Rack

• ensure there are no leaks.  Much easier to do without the engine in the car.  

- Engine and Trans mounts 

Edited yesterday at 05:31 PM by Bake82

[bluecalais79]

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!

[GnatGoSplat]

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.

[bluecalais79]

You are correct on that point, I will be checking my local independent shops to see if they want the job. Not everyone wants to work on these. The first thing I will hear is the job would cost more than the car is worth. I bought this car new in 1994. I gave it to my dad in 2012 who in turn sold it to my brother in 2018. My brother did a swell job of running it into the ground, but when my dad passed away 1/2020 my brother didn't want the car anymore and  showed up at my house a month or so later and handed me the keys. That makes me the 1st and 4th owner.

There is no mechanic on this earth that's going to be successful in convincing me that any job needed to be done on this car will exceed its value. I watched a 24 minute video earlier today on how to do this job. II won't be doing it as a result of watching it. These videos are valuable in that respect as well. 

[bluecalais79]

UPDATE - I believe I may have found a shop with a mechanic having the experience to have worked on these motors that will do the job. My first hunch was to go to a Chevy dealership as the Lumina had these motors as well, those Z-34's you almost never see (?). As soon as they found out I was in no rush to get the car back, they were more open to the idea of working on it. I guess they thought I wanted it done yesterday. Not the case, anytime between now and July 22 will do........

Stay tuned

Edited 1 hour ago by bluecalais79

[94 olds vert]

I was able to replace the o-ring and add an extra gasket with the information from the old double gasket thread all without removing the rear head. I also put RTV on it and it never leaked in the 10+ years I owned the car after the repair.