Engine Valve Cover Leak

Factual Questions
1

On my 02 Cavalier (4 cyl) I noticed that the valve cover seeps a small amount of oil by the seams. Not enough to cause any significant loss between oil changes though. I am quite tired of taking it in to fix little issues. I already ordered the new gasket and materials, its quite simple to replace, and am doing so just out of fixing something that isn’t right, but my question is this;

Can a leaky valve cover gasket cause compression or vacuum issues thereby hampering performance?

Can air entering under the gasket seal (or lackthereof) cause a CEL (check engine light) or issues with any of the emissions control?

Thanks everyone!

2

Certainly not compression issues. That would be caused by valve, head gasket, piston/ring problems, or cracked blocks or heads. I suppose the leaking valve cover could let unmetered air into the engine which could cause a lean burn condition and trip a check engine light. I had something similar happen when unmetered air entered my engine through a failed gasket in the oil fill tube. I’ve never actually heard of a leaking valve cover gasket actually tripping a check engine light though.

3

If the valve cover gasket is leaking oil into the spark plug holes, the oil can contaminate the connection to the plug wires or coil and cause a misfire condition.

4

Assuming the valve cover is this sheet metal be careful not to overtighten. Doing so will distort it which will make a good seal impossible.

5

No.

Not likely. Willcross discusses about the only scenario that might cause a CEL.

6

If you haven’t done so recently, check the PCV valve. When one of those gets clogged, it can cause oil to start seeping out of just about everywhere on an engine.

7

I’ve never seen oil cause a misfire. It can cause plug wires and plug boots to swell, but it won’t affect their function.

8

Apparently I am either partially blind or this car doesn’t have a ‘standard’ PCV setup. All I can see that would be functionally similar is a short hose about 24mm in diameter connected to the intake resonator and the top of the valve cover. Can’t even find the parts for it on RockAuto… wtf. I suppose when I take the valve cover off to scrape and clean off and put a new gasket on I will check to see if that hose is clogged up… Any ideas? If this is it? Not really a pressing issue, but I like learning more.

I found a picture of an 02 cavalier under hood; the middle upper of the picture, see that little hose?
https://images.duckduckgo.com/iu/?u=https%3A%2F%2Fupload.wikimedia.org%2Fwikipedia%2Fcommons%2Fd%2Fd7%2FChevrolet_Cavalier_2.2_L_OHV.jpg&f=1

9

Its aluminum, not so worried about that, maybe have to be careful with the gasket scrape though :rolleyes:

10

no, that looks about standard. that little hose is upstream of the throttle so it’s actually the breather hose; a source of fresh filtered air to regulate and maintain crankcase pressure. the actual PCV valve/hose is probably under the intake duct; it requires intake manifold vacuum to work and will be plumbed to somewhere after the throttle body.

edit to answer your other questions:

it’s possible, but it would have to be such a massive leak that you’d have oil all over the place.

11

Thanks for the responses everyone!

jz78817, I looked around and can’t find it for sh*t. I keep reading this car as an oil/air separator in the valve cover and not a PCV (only models 1998 and below). I suppose I am going to check around more when the parts come and clean out the throttle body as well since I am going to be fiddling around and I am almost positive it has never been cleaned. Thanks!