Oil leaked on me twice on the valve cover passenger side near oil fill cap. PIC>

[5ABI VT]

Hi guys yesterday I drove the car over 1000km to and from an airport half mile event and the only issue I had was twice I noticed a little oil burning smell and when I popped the hood I found oil on the valve cover near the oil fill cap. The cap clicks but is loose /jiggly making me think it's coming from there. There is a catch can on the motor and it did pull about 2 tablespoons.

http://img.photobucket.com/albums/v141/5abivt/Air%20Filters/C17EB61C-A1A6-47D7-BC4F-4E7B09B1CA11_zps2fua7nlk.jpg (http://smg.photobucket.com/user/5abivt/media/Air%20Filters/C17EB61C-A1A6-47D7-BC4F-4E7B09B1CA11_zps2fua7nlk.jpg.html)

Is the oil fill cap tight when you guys tighten yours down ?

[32valvesftw]

I think here is a seal on the cap, maybe it has a crack?

[Dynomite]

A. Billet Aluminum Oil Cap
Search Ebay CORVETTE C4 LT1 BILLET CHROME SCREW IN STYLE OIL CAP Ebay Billet Aluminum Oil Cap (fits 90' & 91' LT5 & L98).
The Billet Aluminum Oil Cap has an "O" ring.

http://i287.photobucket.com/albums/ll142/dynomite007/Dynomite12/Oil%20Cap.jpg

[XfireZ51]

My suspicion is that it's coming from the vent tube. The likely culprit is the vent filter in the cam cover. Ask me how I know. The burning oil smell happens during WOT runs. During cruise, no problem, right?

[Dynomite]

My suspicion is that it's coming from the vent tube. The likely culprit is the vent filter in the cam cover. Ask me how I know. The burning oil smell happens during WOT runs. During cruise, no problem, right?
I would concur but it appears oil has dripped down from around oil fill cap.

[XfireZ51]

I would concur but it appears oil has dripped down from around oil fill cap.

True Cluff, but it would not have gotten over by the cam cover bolt and into the spark plug valley. You can also see some seepage right by the vent tube as it enters the cam cover.
Something is causing a pressurization of the crankcase and I don't think it's the oil cap.

[5ABI VT]

I think here is a seal on the cap, maybe it has a crack?

Looks like it has hardened but the o ring is there and not torn. When the cap is tight .. It jiggles sideways and up and down a little bit like its loose even after it clicked in after tightening.

A. Billet Aluminum Oil Cap
Search Ebay CORVETTE C4 LT1 BILLET CHROME SCREW IN STYLE OIL CAP Ebay Billet Aluminum Oil Cap (fits 90' & 91' LT5 & L98).
The Billet Aluminum Oil Cap has an "O" ring.


http://i287.photobucket.com/albums/ll142/dynomite007/Dynomite12/Oil%20Cap.jpg

Will look into that thanks ! I don't want a billet cap but I can probably pc it to match. In the meantime it might have to do !

My suspicion is that it's coming from the vent tube. The likely culprit is the vent filter in the cam cover. Ask me how I know. The burning oil smell happens during WOT runs. During cruise, no problem, right?

I thought of this but the little area around the base of the vent tube is completely clean of oil.

True Cluff, but it would not have gotten over by the cam cover bolt and into the spark plug valley. You can also see some seepage right by the vent tube as it enters the cam cover.
Something is causing a pressurization of the crankcase and I don't think it's the oil cap.


It's definitely around that area and it's the very first time I've seen it. In response to you again xfirez51 no it doesn't seem to be under wot. I did 3 half mile runs and some more wot back down the runway and when I popped the hood all day between runs the cam cover was clean.

I noticed the first time after steady highway cruising after about 250 miles just pulling into a rest stop. It looked the same as it did when I took the pics I posted above. The second time was when I almost reached home dropping off my friend at home. I'm wondering if it could be from hard braking ? Would enough oil reach the oil fill cap?

I'll take a video of how loose the cap is when I get home from work.. Just curious if it's normal. Thanks everyone for the input!

[A26B]

I looked at your thread discussing your plans for oil catch cans. Can you show a diagram and/or photos of what you actually did?

FWIW, I don't think it's a good idea to put catch cans on the cam cover fresh air inlet tubes. I think it will hinder the function of the PCV system by adding restriction to the fresh air plumbing.

[5ABI VT]

I looked at your thread discussing your plans for oil catch cans. Can you show a diagram and/or photos of what you actually did?

FWIW, I don't think it's a good idea to put catch cans on the cam cover fresh air inlet tubes. I think it will hinder the function of the PCV system by adding restriction to the fresh air plumbing.

No catch cans on the fresh air tubes. Just from rear pcv to can and from there to the hard line on the plenum back to the intake

[5ABI VT]

I'm going to pull the o ring off and see if the cap still jiggles around the way it does. I'm assuming the o ring should help it fit a bit snug ?

[5ABI VT]

Ok so I tried pulling the o ring and no flex at all.. Cracked and sure enough it's almost rock hard. I'll head to the local auto specialty store tomorrow to see if they have an o ring similar to this one. When I screw the cap on without the o ring it jiggles the same way with it on.

Here's a closer pic of where the vent tube goes into the cover .. Pretty oil free to me ?
http://img.photobucket.com/albums/v141/5abivt/Air%20Filters/D1E4B310-DAE3-4336-A50A-DB0EAD29EDCD_zpstevqhorf.jpg (http://smg.photobucket.com/user/5abivt/media/Air%20Filters/D1E4B310-DAE3-4336-A50A-DB0EAD29EDCD_zpstevqhorf.jpg.html)

[Dynomite]

There are several of us that have the stock Oil Caps sitting on the shelf or somewhere that have been replaced by the Billet Aluminum Oil Cap. I can check my shelf to see where the stock Oil Caps are sitting as you like (90' and 91' Oil Caps) :p

True Cliff, but it would not have gotten over by the cam cover bolt and into the spark plug valley. You can also see some seepage right by the vent tube as it enters the cam cover.
Something is causing a pressurization of the crankcase and I don't think it's the oil cap.

Windage from radiator fans could push the oil rearward on the Cam Covers.
Piston Blow by is causing pressurization of the crankcase and the Cam Covers are vented to reduce condensation through the Air Horn which is normal.

A clogged PCV system could cause Oil leaks in lots of places including the Oil Pan and Cam Covers and the Cam Cover Vent as you describe. His Oil Catch Can could even be clogged up reducing the Positive Crankcase Ventilation through the Plenum Vacuum.

Or....maybe oil was spilled during the topping off of Engine Oil :p

We shall see and a different Oil Cap might work and it might not work but removing the Cam Covers with engine in car is NOT fun. But the saving grace with this LT5 is that the Cam Covers have already been removed once with NEW SS Allen Head Cam Cover Bolts which would make it pretty easy to remove Cam Covers with Engine In Car to replace the Cam Cover Vent Filters.

Marc Haibeck Cam Cover Vent Filters (http://www.zr1specialist.com/HAT%20Web/products/cam%20cover%20filter.htm)
Jerry's Cam Cover Vent Filters (http://www.jerrysgaskets.com/filter-cam-cover-vent-90-95-1b4/)

For others watching....Jerry has the SS Allen Head Cam Cover Bolts as well as other SS Allen Head Bolts for other LT5 components.

Jerry also has New and Used Oil Fill Caps of which the 90'-92' are different than the 93'-95'.

[XfireZ51]

In one of the times I did an upgrade on my motor, I used ScotchBrite as a filtering material for the cam cover vent tubes. Shortly after I began smelling oil burn whenever I went WOT. Also had a small oil leak that seemed to be coming from front right hand corner of motor. Had oil pooling on cam cover in very much same manner that you see in the pics above. I was able to remove the passenger side cam cover and replace only the ScotchBrite material in that cover and that seemed to be enough to stop the leaking. Later on, I did a cam upgrade, so I replaced both sides with foam material from Marc H. I also used some black RTV on the front right hand corner oil pan stud.

[5ABI VT]

Catch can is pulling oil still and doesn't seem to be clogged. I am using a larger diameter hose to and from the can so shouldn't be a restriction there I think. I picked up a few o rings and will try them out. The original is hard and I'm hoping it's the reason. The vent tubes.. If oil was leaking out of them I would assume there would be even a trace of oil right at the point where the tube goes into the cover? There isn't any there at all. I pulled plug wires and happy to see they're all clean of oil so it was just the little bit that was visible.

Can anyone verify that the oil fill cap when removed is basically 2 pieces and not 1 solid piece ? Mine jiggles and the inner piece looks to be held by the cap by tabs.

http://img.photobucket.com/albums/v141/5abivt/Air%20Filters/0E08F65D-0F46-4C86-9B91-843EB8B7544C_zpsxstlkdm3.jpg (http://smg.photobucket.com/user/5abivt/media/Air%20Filters/0E08F65D-0F46-4C86-9B91-843EB8B7544C_zpsxstlkdm3.jpg.html)

[We Gone]

Yes the oil cap is two parts much like the gas cap with the top half acting like a ratchet so you can't over tighten it.

[secondchance]

I would also check PCV valves and make sure they are not gunked up.

[5ABI VT]

Well I got the best fitting o ring on the cap and there is a VERY noticeable difference. When tightening I can fee the o ring get snug / some resistance and then it clicks. Never did that before. I cleaned everything up and will get on it a few times tonight after work if I get a chance and check.

Pcv valves were left in sea foam solution for a long time while I did the top end pull. They seemed to be clean but doesn't hurt to check!

[XfireZ51]

I'm hoping you find it to be the oil cap.

[5ABI VT]

I'm hoping you find it to be the oil cap.


I certainly hope so ! My dipstick doesn't stay put either . I'll be pulling it off and sending it out to lokar maybe this week for a screw in billet unit. I will be asking them to take measurements etc so others here can buy one as several people have expressed interest. I don't think I'm leaking from the dipstick though because everything in the area is dry.

I have a feeling braking plus rev matching and downshifting and Loving the rumble my car makes is responsible for oil getting to the front of the cover and leaking through the cap. That's my best guess this far.

[XfireZ51]

I certainly hope so ! My dipstick doesn't stay put either . I'll be pulling it off and sending it out to lokar maybe this week for a screw in billet unit. I will be asking them to take measurements etc so others here can buy one as several people have expressed interest. I don't think I'm leaking from the dipstick though because everything in the area is dry.

I have a feeling braking plus rev matching and downshifting and Loving the rumble my car makes is responsible for oil getting to the front of the cover and leaking through the cap. That's my best guess this far.

Dipstick popping is another sign of crankcase pressurization.

[32valvesftw]

My initial thought was High crankcase pressure, but first rule of troubleshooting is start with the easiest thing first. Maybe it is those vent filters. If it was leaking out your dipstick I would be worried.

[5ABI VT]

The dipstick handle and surrounding area are clean. It just pops out a tiny bit. Seems when I push it in it doesn't really click or want to stay put.

I guess the interesting part is after wiping it down the first time .. I got to the event and did 3 wot runs including some decceleration through the gears for the cameras :) .. Drove about 2 hours from the event mostly steady cruise and some wot to pass people .. And once for a car full of guys who stuck iPhones out to hear it and see it go lol.. And when I stopped at the rest stop it was still clean. From then on it was all freeway all the way home say another 2.5 hours .. When I pulled up to drop my friend at home I got a whiff of the oil and there was a bit more on the cover again. About the best I can describe the driving conditions .