My engine needs diapers.

[Leevon]

I am on a mission to cure my '87 w/ 305 TBI of oil leaks. I hate them.

I started by replacing the oil pressure sending unit which was definitely spewing oil.

Still leaked.

Then I did the rear main seal (one piece) and the oil pan gasket.

Still leaked.

Thinking it might be the famous back-of-the-intake leak, I replaced the intake gaskets, and the valve cover gaskets too.

Still leaked.

Thinking I might have fouled up the intake install I did it again.

Still leaked.

Then I took it to the shop down the road to see if they could find the leak. He thought it was the rear main seal so I did it again. I found a piece of the old retainer gasket on the block, so I thought for sure I had found the problem.

Still leaked.

Then I found a bolt that was poorly sealed on the intake (there was oil pooled up) and fixed that. Thought for sure this was it.

Still leaked.

Then I replaced the distributor base gasket which had been done with the intake but it was discolored like oil was going out the back.

Still leaked.

Then I removed, cleaned, and sealed the dipstick tube.

Still leaked.

It only leaks after driving, and it's coming off of the starter. The back of the intake, sending unit, rear main, distributor, etc. are all clean. This engine is pretty clean and I should be able to see a leak.

I have had it on a lift, on stands, lights above and below, and the leak cannot be found but it's definitely on the back above the starter. To top it off, after driving it shortly today, when I parked it puked coolant. Could I have a bad head gasket, which is leaking oil down the back of the block, onto the starter, and now could be causing overheating?

[Lt.Del]

Wash the engine very well.  Take a digital camera and take pics all over the back of the engine block, heads, intake, etc... You can fit a small digital camera in tight places and just push the button.
Or take some mirrors and try to look around the engine.

[TexasRed]

maybe a crack in the manifold?

[eventhorizon66]

Not to be smarty, but are you certain it's an engine oil leak?  What about the front seal on the trans?  Is the trans fluid still nice and red?  If not, it could conceivably be mistaken for motor oil...except it has its own unique smell and taste .

[Leevon]

Wash the engine very well.  Take a digital camera and take pics all over the back of the engine block, heads, intake, etc... You can fit a small digital camera in tight places and just push the button.
Or take some mirrors and try to look around the engine.

Good idea. 

maybe a crack in the manifold?

It looked good when I had it off. 

Not to be smarty, but are you certain it's an engine oil leak?  What about the front seal on the trans?  Is the trans fluid still nice and red?  If not, it could conceivably be mistaken for motor oil...except it has its own unique smell and taste .

I would wonder the same, but I just went through this routine with the trans too, it's clean.  There's definitely fresh oil coming down the back of the block onto the starter.  I've never seen a head gasket do this, usually it's coolant in the oil or coolant on the ground but this is just crappy.  I really don't want to pull the engine because it would cause me to upgrade to a 350...then I would want a mild cam, and headers, and of course the chip, and well the wife just ain't having that right now. 

[bigkountry]

Are you sure the lip on your valve covers are not warped from someone over-tightening them?

[camdenoilchange]

i've seen a head gasket do this once, not on a chevy, but still possible. double check your valve cover and head gasket imo. if that doesn't work, hold the gas to the floor and blow it! then the wife will have to go for the 350!

[VileZambonie]

Get a bottle of engine oil dye tracer and a uv light. Then you will know for sure the source of the leak.

[Skunksmash]

To top it off, after driving it shortly today, when I parked it puked coolant.

This made me laugh. Be funny if you replaced the engine with that new 350 and it...


Still leaked.


Naw but seriously if you try everything (including the UV light) you may just try eating the price and take it to the chevy dealership. They have to warranty their work, and sometimes after you pay once if it does not fix it they have to continue trying, for free. Unless they find out that it was something totally different, in which case you are still happy cause they fixed it. It's a good option, if you have the money. I have had to do it before, and that's the way it worked out for me so i just thought i would throw it out there. Besides, their "diagnose" price is only 70 bucks anyway. That right there might be worth it cause they may just tell you what the heck it is, and then you can fix it.

[rockable]

http://forum.73-87chevytrucks.com/smforum/index.php?topic=9169.0

I'm wondering what you finally found.  I'm on a similar odyssey.  I've replaced the pan gasket, rocker cover gaskets, intake gaskets and distributor gasket on my '86 and still have that pesky little puddle under the torque converter inspection cover every time I park it. 

I'm definitely gaining on it but I haven't closed the final gap.  I also haven't replace the rear main seal yet.  I really was hoping I wasn't going to have to do that.

Any feedback would be appreciated, also any input from anyone else with similar experience.  His thread was almost identical to mine.

[Russ130]

There is a plug on the back of the motor that is partially covered by the intake. If this were to vibrate loose somehow it would leak oil and since it is under pressure just a small leak would be a considerable amount of oil probably just as much as a valve cover.

[Leevon]

I know this is an old thread, but hey I work slow.  I recently pulled the engine in search of this leak, put it all back together and it still leaks.  I am at my wits end now and feeling like a really bad wrench. 

To recap, the leak is coming from somewhere around the second bellhousing bolt and soaks the starter.  It's NOT as high as the intake or valve cover.  I am also positive it is NOT the rear main.  It also does not leak until the truck is driven at highway speeds and then it leaks bad.  I can let it idle or put around the block and not a drop. 

When I pulled the motor the usual suspects looked good.  Back of intake, sending unit, valve cover gaskets, dipstick, distributor, all clean.  There was some buildup on the passenger side near the rear main retainer but I couldn't track it's source. 

So my question is, could a cracked head or bolt hole in an oil passage cause this? 

[VileZambonie]

Did you install dye tracer?

[Leevon]

Can't get that stuff around here, guess I'll have to do some internet shopping.

[VileZambonie]

Any Napa, Carquest has it.