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As stated in the title as I was removing the valve cover to replace the gasket I noticed this large buildup of a whipped cream consistancy mystery substance on the top of the valve cover. It is also seen at the top of my oil dipstick. My cursory research said this could be due to many short trips without warming up and water in fuel.

This is a 1979 Jeep 4 door Cherokee with AMC 258.

I am just looking to see what you all think this may be from!

It does use some.oil which is why I was replacing the gasket.

Curious to hear what it may be!

Thanks so much,

- Ben

If the oil in the crankcase doesn't look like that I'd agree with the short trips theory or maybe a minor head gasket coolant leak. Bad leak would turn all the oil into butterscotch pudding.

I don't think water in the gas would do that.

I concur, doubt it's as simple as valve seals, that looks like coolant intrusion. Head gasket, at worst cracked head. I would guess the next oil change will tell the true tale. Maybe spin off the oil filter in the meantime and see if there is mung on or in it.

Fleet Fox

Common issue on 258's (And really, any cast iron i6's) that are not driven long enough to get hot enough to cause vapor build up to exit the system through the crank case breather.

Mine used to get it all the time when I work 5 mins away from home. It never actually got up to operating temperature for any length of time.

What I ended up doing was once a week I just went for a drive. After doing this it went away.

Thanks for all the replies thus far.

I do only work about 5 minutes away so it gets a lot of short trips.

Does a longer drive get this burned off? Should I remove what is there?

What should I be looking for at the next oil change?

Thanks again!

A good 45-60min drive should help get rid of it, but will most likely take a few trips. I remember after the first time I did this, when I got home I pulled the breather hose, and you could see some faint steam coming out.

When I changed my oil, I did not see any milkiness in the oil coming out at all. I only noticed it on the oil cap in the valve cover (and on the rockers when I looked inside). Since you have the cover off, I would wipe down as much as I could to remove it.

The reason it happens is the top of the head on an i6 takes a long time to get up to temp. So moisture that gets hot down lower in the crank case will condensate on the rockers. Which then starts to build up.

Great,thanks!

I cleaned it out well and now have a good excuse to take the jeep for longer drives!

Um, you aren't running some low temp thermostat or worse, none at all are you? That wouldn't help your situation.

SJTD wrote: ↑Fri Mar 27, 2020 7:56 pm Um, you aren't running some low temp thermostat or worse, none at all are you? That wouldn't help your situation.

Ahh, good point. Should have a 195 stat in it. Running something lower will make this worse.

If pcv is clogged and Temps are not getting warm enough 210+ water won't evap from oil, older engines that previously used oil with paraffin wax in it can cause that especially under such circumstances.

Water moisture is seeping inside the closed system somewhere, as stated possible gasket leak yet I would look and vlv cover gaskets make sure they are intact.
My 360's all had the silicon OEM materials, so I rowed thru them with the new cork/composition ones.
And PVC vlv itself and all hoses, PVC grommets, that are on system.
1st thing I did on ALL my jeeps is replace EVERY hose and rubber piece on the entire truck, everything, I learned piece meal replace things was not sufficient, SHOT-GUN was the best choice on this.

Looks like water in the oil to me; been there before. It’s the classic baby poo sign.
Is your radiator low? Does it blow white smoke out the tail pipe?

When the engine cools it pulls in air from the environment [mufflers do the same thing]. When the air cools the moisture condensates and settles on the inside of the motor. Running the engine long enough to reach operating temperatures will vaporize the water again releasing it and will get sucked through the intake/PVC/combustion circuit. Note: it doesnt have to reach boiling to vaporize