68 307ci oil foaming at oil filler neck - The 1947 - Present Chevrolet & GMC Truck Message Board Network

soba_03 · 10-30-2007, 02:04 PM

Ok here is what I got, the PCV valve is new and plumbed correctly into the air cleaner. Earlier today I noticed that I have some oil foaming in the oil filler neck. Now this would not concern me much. But i had to fill the radiator up. Here is what i know. I had to replace the carburetor because it was running lean (sucking air) this caused the truck to run hot. So I wasn't concerned when I saw the radiator down a bit. I don't have an overflow bottle, it vents on the ground. So low is to be expected.

But I put about 1/2 a gallon of antifreeze, and checked the oil, down just a smidge so I went to add and the filler neck was foamed and I immediately trickled down my leg....

I have not owned the truck to long, I'm not seeing anything otherwise to be concerned with. I'm thinking that this is to be expected.. Please confirm or deny my thoughts..... am i going to have a problem with this?

Regards,
Soba

ChevLoRay · 10-30-2007, 02:16 PM

Describe "foam". If you are talking about a milky substance on the bottom of the oil fill cap and just inside the top of the fill tube, I don't think it's anything but normal condensation that you see. Oil plus condensation will be milky and that's it. If you pull the stick and the oil you see on the dipstick is milky, that's different.

With the recent change in weather, you may be seeing some condensation that you have not noticed before. These engines are much more open to the atmosphere than are those in our newer vehicles. As such, we will see more effects of that exposure.

So, what are you defining as "foam"?

dfosh · 10-30-2007, 02:17 PM

How hot did it get? If the temp went up quite a bit ,you may have cracked a head . This would let water and oil mix causing the foam in the oil. Other members may give you some other ideas.

dh81k30 · 10-30-2007, 07:11 PM

Quote:

Originally Posted by soba_03

Ok here is what I got, the PCV valve is new and plumbed correctly into the air cleaner.
Regards,
Soba

Soba,

The PCV valve should be plumbed to manifold vacuum and the breather vent goes to the air cleaner.

Maybe this will help,

68gmsee · 10-30-2007, 07:58 PM

Keep a good eye on it. White milky foam stuff in the oil, valve cover caps, etc.. indicate moisture getting in there. More than likely a cracked head or bad head gasket. The only way to find out for sure is to do a leak check on it.

Aside from that, you will have to dismantle the engine and check the heads and gaskets.

10-30-2007, 02:04 PM	#1
soba_03 Registered User Join Date: Sep 2007 Location: Fairdale, Kentucky Posts: 560	68 307ci oil foaming at oil filler neck Ok here is what I got, the PCV valve is new and plumbed correctly into the air cleaner. Earlier today I noticed that I have some oil foaming in the oil filler neck. Now this would not concern me much. But i had to fill the radiator up. Here is what i know. I had to replace the carburetor because it was running lean (sucking air) this caused the truck to run hot. So I wasn't concerned when I saw the radiator down a bit. I don't have an overflow bottle, it vents on the ground. So low is to be expected. But I put about 1/2 a gallon of antifreeze, and checked the oil, down just a smidge so I went to add and the filler neck was foamed and I immediately trickled down my leg.... I have not owned the truck to long, I'm not seeing anything otherwise to be concerned with. I'm thinking that this is to be expected.. Please confirm or deny my thoughts..... am i going to have a problem with this? Regards, Soba

10-30-2007, 02:16 PM	#2
ChevLoRay Old Skool Club Join Date: Jun 2001 Location: Benton, AR "The Heart of Arkansas" Posts: 10,880	Re: 68 307ci oil foaming at oil filler neck Describe "foam". If you are talking about a milky substance on the bottom of the oil fill cap and just inside the top of the fill tube, I don't think it's anything but normal condensation that you see. Oil plus condensation will be milky and that's it. If you pull the stick and the oil you see on the dipstick is milky, that's different. With the recent change in weather, you may be seeing some condensation that you have not noticed before. These engines are much more open to the atmosphere than are those in our newer vehicles. As such, we will see more effects of that exposure. So, what are you defining as "foam"? __________________ Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was.

10-30-2007, 02:17 PM	#3
dfosh Registered User Join Date: Oct 2007 Location: greeneville tn Posts: 237	Re: 68 307ci oil foaming at oil filler neck How hot did it get? If the temp went up quite a bit ,you may have cracked a head . This would let water and oil mix causing the foam in the oil. Other members may give you some other ideas.

10-30-2007, 07:58 PM	#5
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: 68 307ci oil foaming at oil filler neck Keep a good eye on it. White milky foam stuff in the oil, valve cover caps, etc.. indicate moisture getting in there. More than likely a cracked head or bad head gasket. The only way to find out for sure is to do a leak check on it. Aside from that, you will have to dismantle the engine and check the heads and gaskets.

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