Oil Fill Cap Question

[ruralcarrier]

Not sure is this is the proper place but I will give it a shot since it does deal with the lubrication system.

I have a 2006 Pontiac Torrent with a 3.4L engine. This past summer the engine got hot for no apparent reason. As long as I was moving it was not a problem but any idle time and the temperature went up to the point the idiot light came on. I did NOT drive the car after this but took it to my trusted mechanic. The diagnosis was a blown head gasket in cylinder #1. The repair was done alone with an oil and coolant change. I had been using Kendall 5w30 semi-syn and that was replaced with PYB. Immediately after this event the oil fill cap would not come off. It attaches into about a 3-4 inch neck and everything, cap and neck would unscrew. I finally got the cap separated and noticed the inner side of the cap was very discolored, almost like it had been burnt. This is a vented cap from what I can tell. I ordered another GM cap and replaced the old one. This cap is easy to remove and is a nice white color inside.

My question basically: Could the overheating have caused the old vented cap to fail or could the failed vented cap have caused the head gasket problem?

I have noticed with the new cap that when I remove it there seems to be a lot of moisture inside, is this normal and the function of the vented cap?

I contemplated replacing the original cap with a $5 aftermarket but it was not vented and did not have the o-ring attached so I went the OEM route.

What is the purpose/advantage of a vented cap as no other vehicle I have seems to have this style?

If this is on the wrong forum, I apologize and I also appreciate any response.

Thank you.

 

[Ursatdx]

I have never noticed a vented cap on any GM vehicle.
It is common for the caps to bond with the fill tube and
when you try to remove the cap the tube, instead, comes off.
A bit of oil on the rubber o-ring on the cap may help.
The moisture you are seeing on the cap is something I often see.
The highest point in the engine that is subject to crankcase vapors
is usually the area in which moisture will gather. Take a look at your
PCV system to be that is functioing properly.
Do you "short trip" alot? Letting the engine reach operating temps
will help to reduce moisture in the crankcase/engine.

 

[hisilver]

Maybe your overheating issue melted the cap. Also they do get discolored and gross
as time goes by.

 

[ruralcarrier]

Tried lubrication on the old cap and it made it only marginally better. Most trips are 10+miles and several highway trips of several hours.

This same cap goes on many GM vehicles and I guess the venting adds to the price, along with the GM name.

The old cap did not have the moisture I see with the new one but a thick, pale yellow build up even after cleaning and a couple of 20 mile trips.

 

[silverrat]

Can you post an image of what you consider a vented oil cap?

 

[ruralcarrier]

picture

The picture of the cap upside down shows the inside and the vent from what I understand.

The PCV valve is held in with some type of bracket and not sure how to remove it.

 

[440Magnum]

Vented oil caps went away by the late 60s. My '66 has one, my '69 doesn't (uses a filtered PCV inlet from the air cleaner to prevent blow-by from escaping to the environment when manifold vacuum is low and the PCV can't keep up.)

Unless the OEM cap has a hose attached to it that goes to the air intake tract, its not "vented."

 

[ruralcarrier]

My mistake then but what is the device inside the cap? The OEM cap looks nothing like an aftermarket cap.

 

[Kira]

As ursatdx said, those oil fill tube extensions come out when you try to remove the fill cap.
Try using silicone grease on the cap. It's what I used on a friend's S-10 4.3. So far so good. Kira

 

[ruralcarrier]

Here is a description of the this cap (that fits multiple GM vehicles) and the term "vented" is used.

Part # 12589430

CAP,OIL FIL(SAE 5W30, VENTED, W/SEAL)(ACDelco #FC219). CAP-SEAL, Engine Oil Filler. For: L 3.4F(LNJ) (2006-2009) (2006 - 2006). Required: 01

 

[ruralcarrier]

Well, with the new cap installed the tube does NOT come out now and never did before the overheating situation on this particular vehicle.