STI990

I posted this in the C5 Tech area but have not got much feedback.

I was racing this past weekend at waterford hills raceway and toward the end of the day I noticed that on start up it blew a puff of smoke, the car started to idle with some smoke from the exhaust. I went out for another run and the smoke started to fill the inside of the car and I could see it out the back. When I got back I noticed that the whole front of the motor and underside of the motor and car were covered in oil.

The car is running fine with no codes thrown.

I had it towed home, cleaned it up so I could start to investigate where the oil was coming from. After cleaning I let the car idle and couldn't see a leak from anywhere. I then went for a little drive and when I got back the oil was everywhere. I am almost positive that it is coming from the front Main seal... similar to this thread https://www.corvetteforum.com/forums/...main-seal.html. I dont think it is leaking till there his more oil pressure/rpms.

Now some history: I replaced this seal and the harmonic balancer with a SLP and have not had any issues till now with this seal, but it is new. I also just started using 50wt at the track, could this create higher oil pressure and cause this to blow? I am seeing high oil temps and will be putting in a dewitts radiator/EOC when I do the front main.

Also I think the smoke on start up was due to the high RPMs and some oil getting into the intake, I looked in the throttle body and intake and found some oil, any recommendations on a catch can? I also replaced the PCV valve today.

I am looking for some advice on why this seal could have went again? I don't want to replace the seal and have it start leaking again.. Also is there a "better" front seal? And where do I get the thin piece of metal that is used if the crank has a groove? Any advice will help, thanks!

Update:

I cleaned everything up and pulled the car on some ramps to look for the leak. I let the car idle and started to see a light film develop on the upper oil pan gasket. I then cleaned this off again and leveled out the car by lifting the rear and watching for the came leak, when doing this I saw little air bubbles coming out between the upper oil pan gasket and the same film of oil being created. I then had the wife rev to about 4k and hold to see if the leak got worse and it didnt. I then went for a quick drive and oil was all over the place again. So 2 theories, this oil leaks under load due to excessive crankcase pressure or its leaking from sloshing around... its hard to believe that its from sloshing around. I have been reading some threads like this one http://ls1tech.com/forums/generation...an-leak-3.html.. which was fixed by opening up the pcv system or this tread https://www.corvetteforum.com/forums/...il-leak-2.html.. where it happened to be a cracked ringland. I am hoping to get a leak tester tonight to see how that goes. If that happens what do you guys think about the pcv venting? Bottom line I will need to get the upper oil pan gasket changed but i need to get this figured out before I replace it and blow it out again.

other thread:https://www.corvetteforum.com/forums...-please-2.html

STI990

Bump

STI990

Leak Down Results: Cold Engine

Cyl 1 – 20%
Cyl 2 – 10%
Cyl 3 – 10%
Cyl 4 – 11%
Cyl 5 – 13%
Cyl 6 – 8%
Cyl 7 – 10%
Cyl 8 – 7%

Not the most confident in my testing but this is what I got

dp201

I had a very similar problem with my 08Z. Came off of the track and had oil blown all over the engine. I finally tracked it down to coming out of the intake and leaking down from the air filter. I always run it close to full at the track because of paranoia about oil starvation. I installed an Elite Engineering catch can and found it to contain about 3.5 oz of oil after a full track day, nothing coming out of the air filter though. After consultation with a well known corvette mechanic, I was told to run it with the oil not so full, about half way up the dipstick. This seems to have solved the problem of the oil blow by but not my paranoia about starvation. Every time that I found oil in the can or coming out of the intake, I would add more oil to the reservoir which just continued the cycle. I also had the front seal and pan seal replaced which was a contributing factor but did not solve the blow by problem.

STI990

Ye amine is not coming from the filter area thats for sure, but i do keep it a half quart or so over filled cuz I track it a lot... one of the things I was going to do al is just run the 7 quart standard fill for now on. I will be adding a catch can and eliminating the pcv valve, I think its a bottle neck in the flow of the PCV system and run the GM oil cap with the pressure relief.

0Anthony @ LGMotorsports

Do the leak down warm and get new results...

If those are real numbers...that engine is very tired.

STI990

I'm not sure how one is to do a leak down hot without burning to death, I was told a cold leak down was fine and should still show relative results...like I said I was not confident with my testing.

Bill Dearborn

Investigate the front cover gasket. I had a similar massive oil leak on my 08Z. It covered the bottom of the car from the front stabilizer bar to the tip of the exhaust. I would go out on track and make a couple of laps, come back to the garage and within 2 minutes of parking there were large puddles of oil forming on the concrete. The bottom of the car looked like somebody took a spray gun and sprayed oil all over the place. Mostly on the driver's side but a fair amount on the passenger side. Dealer mechanic thought it was oil cooler and replaced it to no avail, then he replaced the oil pan gasket to no avail, then he replaced the front cover gasket and that resolved the problem.

Bill

blkbrd69

Try checking crankcase vent system to make sure its not blocked. Pressure buildup can push any gasket out of the way.

Oil shouldn't make much of a difference. Most of the seals really are not holding oil pressure, they are holding crankcase gas pressure.

Unless you did a cam or otherwise disturbed the pump seal at the pan?

Are you sure that balancer is tight?

0Anthony @ LGMotorsports

Just need to get the block and heads to 'grow' so everything is more at their natural size.

Not saying take it apart after a run at the track but not stone cold.


If you are seeing those kinds of leak down numbers then my guess is you have to much crankcase pressure and it has started to blow out seals. Taking the time to replace a front cover/balancer/rear main seal is not going to fix a leak down/bad ring issue.

I do agree that you need to check all of your vent lines and make sure they are ran right and that nothing is blocked.

dp201

What would be the proper procedure for checking the crankcase vent system for a blockage?

C66 Racing

I am having a similar problem and have been reading threads on this issue dating back 8+ years.

Are you sure you didn't pop the rear seal (see my story below)?

I have been fighting this issue since the beginning of last season and really haven't had the time to dig into it.

Summary of my history:
- 2003-2013
Raced SCCA T1/T2 with a stock engine, stock PCV and passenger side vent line, no catch can. Always took about 1/2 to 1 qt down the intake during a race, but managed it.
- 2014
Switched to NASA ST2 and modded engine (~400 rwhp on very conservative tune) with forged pistons, rods, Comp Cam, Comp Cam lifter/valve springs, Texas Speed pushrods, high flow oil pump, and catch can on passenger side valve cover. Car also now has aero (splitter, wing). With this setup I immediately had problems with excessive oil carryover via the passenger side vent into the catch can - would fill the can in ~3 laps.
- Tried no catch can and sucked massive amounts of oil into intake on long left high rpm corners.
- Had DRM fabricate a special very large catch can - doubled the length of time but still filled it well before end of race and sucked oil into engine.
- Tried plugging passenger side vent and using only PCV - blew aft main seal. Amazingly it popped to relieve pressure, then resealed. Tons of smoke everywhere, but didn't replace the seal and ran the rest of the year (three races, one DE).
Managed to limp through the year by short shifting and running a gear over pretty much everywhere - not very fun.

After the season I had a little time to research. I learned that while my VIN is an 02, in 04 GM deleted the PCV and put an orifice in the valley cover. Not knowing this, when I put a crate motor in my car in 04, I put the PCV back on. So from 04-14 I was using an orifice (verified at end of season tear down) and a PCV - probably really restricting that vent path.

I bought an Elite Catch Can with their oil filler cap vent which raised the stock passenger side vent by ~4-5" (as the stock vent has a baffle inside the valve cover that is ~1" below the top of the valve cover). I removed the PCV (leaving just the 04 orifice in the valley) and did a DE in Nov with this setup - ran fine at Summit in the 1:19s at race distance and only picked up ~1" in the catch can. Thought I was done!

Raced 5 races at Summit and VIR this year. Noted that over the course of the season my catch can was getting more and more full at end of race. Not sure why. Maybe rings wearing? Maybe getting hotter (was 92F at VIR last Sunday). Last weekend at VIR on lap 7 I blew the aft main seal again - tons of smoke, but like last year it resealed and I limped it to my trailer.

My thoughts after reading dozens of threads on this topic dating back to ~2005 or so.
- LS6 puts a lot of oil in the passenger side valve cover.
- At high rpm, long left hand corners the oil is held on the outside of the valve cover and doesn't drain filling the valve cover.
- My brother-in-law (my engine builder) believes that the crankcase has more pressure now than stock as my cam is very aggressive with lots of lift/duration.
- The PCV line alone cannot relieve pressure.
- When the passenger side valve cover fills up, that line doesn't vent pressure well as it is mostly pushing oil not air.

I am leaning towards trying a 2nd catch can ported to the aft of the driver's side valve cover (which is plugged on the stock LS6) and T-ing this with the catch can outlet from the passenger side valve cover (Elite Oil cap) back into the intake. My thought is that in long left hand corners the driver's side vent may relieve pressure thus providing less motive force to push oil out the passenger side valve cover (and opposite on right hand corners).

Anyone tried this or have thoughts on it?

If that doesn't work, I am getting a two stage dry sump for next year.