3400 oil leak

[Kaiju Senso]

I have a 2005 3400 (Equinox LNJ) in my Fiero with a manual transmission running a 98 OBDII PCM. The motor barely has a few thousand miles on it (estimation based off information I gathered when I snagged the engine) It has been sitting in the basement of the university's engineering building, climate controlled, since 2005. I've had it running in my Fiero for about 800 miles and doing my spring check over after sitting in winter storage, noticed this.



The engine is incredibly clean, no oil running down the side of the block that I can tell so it looks like the oil is coming from between the trans and block. This leads me to believe it's the rear main seal. It isn't leaking all that bad, noticed some drips but not puddles.

Should I try some stop leak additive? Replacing this seal is a big job right? Is there anything else I should check and look to replace? I just got the car out for spring and I'd really rather have it to drive until winter when there will be plenty of time to drop the drive train again.

[unchained01]

Looks like a rear seal or pan gasket to me.

[Kaiju Senso]

The question still stands, is it an ok idea to try some stop leak oil additive with a basically new motor?

[pocket-rocket]

I personally wouldn't chance it on my vehicle or one that belongs to anyone else, but that's me.

Band-aiding doesn't fix the problem, it's just a temporary solution. Not to mention what it could do if that stuff decided to clog an oil passage somewhere.

[Kaiju Senso]

Is the rear main seal a 1 or 2 piece? Someone suggested I might be able to replace it by just removing the oil pan, does this sound plausible?

[3400-95-Modified]

Its a one piece seal, you can't replace it unless you remove the trans.

That could also be the Oil pump drive o-ring seal leaking on the top of the engine and the oil is just going to the lowest point. I'd check that first since those O-rings are known to leak.

I noticed some oil on my engine this year... not bad for two full years on a build before anything leaked, and I think its all coming from the LIM valley seal where you put the silicone. I think I barely got that sealed when I did it so now it's starting to leak.

[carbon]

Rear main is one piece and needs to go over the crankshaft... its not going to happen without removing the transmission.

I though I had a bad rear main and it turned out that the oil pan gasket had gotten pinched when it was loose while doing the front main and timing chain... that was on an iron head 2.8 though.

[neophile_17]

My pan looks like that too, although it's got a 100,000 more miles than yours. I'm pulling it this weekend to put in the race-car. If I figure out where it's coming from I'll let you know. Personally I would drive it as is. Mine doesn't leak enough to lower the oil level and I didn't notice oil stains where I usually park. Could be it seeps enough in storage to cause this but with normal driving it's fine.

~sam

[Kaiju Senso]

Its a one piece seal, you can't replace it unless you remove the trans.

That could also be the Oil pump drive o-ring seal leaking on the top of the engine and the oil is just going to the lowest point. I'd check that first since those O-rings are known to leak.

I noticed some oil on my engine this year... not bad for two full years on a build before anything leaked, and I think its all coming from the LIM valley seal where you put the silicone. I think I barely got that sealed when I did it so now it's starting to leak.

Thanks for the idea, just went out to check. Couldn't see any oil on the block or heads in that area, got my fingers all up around the hole and not a drop of oil.

This motor is still factory fresh, perhaps could the oil be coming from the transmission? I did power wash it and paint it (with the axle holes capped) when I did the motor swap. Maybe the input shaft or axle seals are leaking on it? Its got 94k miles on it. Hmm I think I'll go back out and check the fluid level in the trans, just nervous to lose the VSS gear into the trans...

**
Ok checked the trans fluid level and it was low (still above the VSS but below the lines on the shaft) so I bet that's where the oil is coming from. I added some leftover synchromesh and I'll check it again this weekend. Either way looks like I should drop the cradle and have a look. Should be really easy this time with all brand new bolts.
**

[1988GTU]

If the other suggestions dont help, checl the rear valve cover seal, intake tube breather (sits in the rear valve cover) or the seal around the trans input shaft.

[3400-95-Modified]

One more area to add to it, since I think its where I'm leaking from, is simply the lower gasket valley... depending on how that was done, it could be cracked or starting to seep... I think thats where my oil is coming from so next time I'm going to attempt to install the 3500 valley gaskets on my 3400 block.

[TGP37]

I found my crank sensor (the 7x one) leaking the other day. I never would have guessed a sensor above the oil level would leak so much.

It was hard to diagnose until I got my head under the engine while having it run at 2k rpm.



Just a thought, place to check. I used black RTV and it sealed right up good.