GMC S15 2.8 v6 leaking oil rapidly while running

[Chris]

As you probably noticed by the title, I have a GMC S15 that leaks oil rapidly while running and a small amount right after the engine is shut down. After crawling under the truck to see where the leak is coming from, the leak looks like it’s dripping down from the space between the engine and the transmission. I fear that it may be the rear seal, but others have suggested it is some type of seal having to do with the distributor.

Some more info on the truck: Before I started working on it, the truck sat for up to 10 years. (it sat because the fuel pump went out). It started leaking after an oil change and a few runs (I put synthetic in it which probably contributed to the leak). The leak is engine oil and it is fresh. I cleaned the surface as best I could then took it for a small drive. After the drive, I looked under the truck and saw that the leak had continued right where it was before.

Tell me what you guys think.

Topic

[college man]

It could be the rear main seal. Do you see oil around the distributor?
see if this link helps.

http://www.ericthecarguy.com/faq/finding-and-fixing-leaks

[EricTheCarGuy]

With oil leaks, always start high. In your case you might want to get a closer look at that distributor before you go for the rear main seal. Also check the valve covers and whatever else seals on the back of the engine there. More info in the article College man posted for you.

Good luck and keep us posted.

[Mike]

Usually, there’s a sheet metal access plate on the forward face of the bell housing, at the bottom. (It’ll be be a real cheap tinny affair, like something cut out of a coffee can.) Typically held on with 3 or 4 bolts, and super easy to get at and remove. Remove the plate and look up inside there with a good bright flashlight. If you see oil inside the bell housing, it’s a pretty certain bet that your crankshaft rear seal has expired.

If the inside of your bell housing is dry, you can forget about the rear seal for now, and look for external leaks further up the engine block and heads. If there isn’t anything obvious there, you’ll want to consider your oil pan gasket.

When probing around nooks and crannies where you might not have a direct line of sight, a bright flashlight and a mechanic’s mirror on a long stalk handle are very useful items.

[Chris]

Thanks for all the useful tips! Unfortunately a fire along with some bad weather in the area has prevented me from making any further progress on my truck, but I will be sure to post what I find.

[none]

I’d also look at the oil sending unit. It might have got brittle and cracked from all the years of sitting.

[Chris]

Okay, upon further inspection through the port that Evil-i had mentioned, I saw a good bit of oil pooled up inside of the bellhousing. It also looks like oil has gotten on the clutch and/or pressure plate because oil reside is all around the entire inside of the bellhouse. This truck is about due for a clutch as well, so I went ahead and removed the transmission (it wasn’t to difficult, about a 2 day job and twenty trips to the tool store for different wrenches). I haven’t removed the flywheel yet, but I did notice something strange: there is a large amount of some type of sealing material (like RTV silicone) sitting on the top-left side being covered halfway behind the flywheel. I’ll attach a picture and show you where I saw it.

Later today I plan on quickly removing the flywheel and pilot bearing. When I’m down there I’ll take a better picture and post it on here.

Attachments:

• image1.png

[Chris]

Alright, so I finally got to taking off the flywheel. Here are pictures of what I found (this is after I replaced the rear main seal):

You can see that silcone stuff I was talking about. There was no oil on or around that area, so I’m just going to leave it alone. The rear main seal was a pain to get out, but after lot of attempts it came out. I’m hoping I put it in square, so that way it doesn’t leak worse than before! 😆 I’m going to put the flywheel on and run the vehicle to make sure it’s not leaking anymore. If everything checks out, I’ll begin to reassble! :cheer:

I hope the neighbors won’t mind me running the truck with open headers for a little while B)

Attachments:

• image1.jpg
• image2.jpg

[college man]

Nice progress. Looks like someone has been in there with all the silicone cake frosting.
You gotta fire the truck with open headers. 🙂 keep us posted on your progress.

[Chris]

Well, looks like the new seal is holding and there aren’t any leaks.

I did end up running it with open headers (which you’ll see in the video) and the neighbors were none to happy about it. Before the video I didn’t realize that the engine fan was rubbing against the radiator fan housing, so I removed that before recording. It ran super rich (or lean I don’t know it just smelled :silly: ), but it was fine for the simple leak test. Hopefully I can get the trans in tomorrow, but I’m waiting for a new slave cylinder from rock auto.

Anyways, hope you enjoy the video. I was the one recording. I hope you enjoy my excellent narration 😉
[video width=425 height=344 type=youtube]hYUZrZ3v8XA[/video]

[Mike]

As with all GM engines, they sound best after they’re shut off. :whistle:

[Chris]

[quote=”Evil-i” post=143295]As with all GM engines, they sound best after they’re shut off. :whistle:[/quote]

Is that so? My neighbors certainly agree with you in this case. :blush:

[Author]

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