so ever since I've owned my 1990, there has always been lots of oil on the back of the engine and it had leaked down.
its got 88k miles, I have not ever noticed a drop in oil level.
A couple months ago I rebuilt the front end suspension and cleaned a lot underneath. lots of oil on some wires and cleaned them up.
couple weeks ago I took it into the shop for some exhaust work (it had burned a hole in my floor pan) and the mechanic allowed me to take a look underneath the car and i noticed the oil was back.

I haven't been able to drive it due to the weather in a long while, came across a video about leaks and decided to check over it today and noticed a couple things.

1. oil looked like it was coming from the bottom of the distributor but not the oil pressure unit. is there a reason for there to be oil coming from there?

2. I had my valve covers powder coated, replaced gaskets (used to leak at covers, now doesn't) , but now has a slight beading of oil around the PCV valve on driver side, and vent on pass side, exactly the same on both sides.
The PCV valve seems to work just fine, no noticeable vacuum leaks. could it possibly just be a loose PCV grommet?

3. I replaced my radiator and put in new thermostat. it seems the thermostat gasket has soaked up coolant and passes right through it, and leaks very slightly. the housing is as tight as it should, maybe a little too tight

I had done a quick convo with my father, I am going to do a compression test tomorrow to check if i could have possible blow-by.
I really hope not because i don't have the time nor any money to do a rebuild right now

 

A compression check wont show leak down or blowby...you would need to do a leak down test and that will tell you everything.....as far as oil leaks, oil has a dye in it already. So get a UV light and start looking. You can also get some dye and add it to the oil. Run the engine then go at it with the light (in the dark is best) and you should clearly see the issues.

 

1. there is a gasket between the distributor base and the intake manifold which may be leaking
2. get new grommets
3. get Mr. Gasket Thermostat Gasket 738G aluminum with silicone seal. I have the no-name ebay version half price, seals 100% and is reusable. Install dry with no added sealant. Torque the 2 housing bolts to 15 ft-lbs, not much needed.

 

Alright, I will go and get a leak down tester. I am also going to do an oil change and see how much I have lost, and I will put some extra dye in it.

 

I'll do all of these with an extra leak down test. I have never heard of the Mr Gasket I'll have to check it out. Is there an easier way of replacing the gasket than having to drain a bit of the coolant?

 

Not much coolant will be lost from taking the thermostat housing off and replacing the gasket. Maybe 2 cups worth when I did it.

 

Shouldn't the china walls be a part of the conversation here??

 

I'll check it when I pull the distributor

 

Also - this was the largest source of oil loss and leakage on my car, an '89....https://www.corvetteforum.com/forums...post1607440651

 

UPDATE:

worked on it all day yesterday, got it tore down and put back together.
I didn't end up doing the leak down test unfortunately, but i put in the new Thermo. housing gasket with an aluminum and silicone one, works great! my other one that I had put in maybe 2 months ago was coolant logged and it had torn its self in half somehow.

pulled the distributor, I do believe that's where my leak was, the gasket was covered in oil. cleaned the area up, cleaned all the connections and put dielectric grease around connections.
in the Dist. hole, there was a hard peanut butter substance on the wall at the top. it seems like its silicone, but I'm not sure why it would be there.
I also tightened up the oil pressure sender as much as i could with what little room i had.
Changed oil, was a little dark for what i would have liked, but still not much oil was missing, nothing to be concerned with, which i find crazy.

put everything back together with new gaskets. it was my first time pulling a Distributor, and everything went pretty smoothly, except for the coolant mess from the Thermo. its all cleaned up again, went for a good little drive this morning, no leaks yet, but i am burning oil off from after cleaning on the exhaust and side of the engine. sometimes i wish it was real simple and easy to pull the engine to clean and paint. but i dont want to do that.

Edit: PCV is no longer leaking after cleaning the grommets, they sealed up nicely

 

That’s one good looking L98. If your leak persists, one of the things I would suggest is the intake china wall like others suggested.

 

Thank you, Ive put a lot of work into getting it to look nice, still a couple things here and there.

I also forgot to mention. I did take a look at the china wall, and it looks like a previous owner had filled it full of gasket sealant at some point, and it looks pretty decent.
I will keep an eye on it every time I drive it