White Foam in Oil Cap

There are several possible causes, including combinations of the possibilities:

- Motor oil level is too high

- A motor oil additive is causing the foaming

- There is coolant mixed with the motor oil - check the oil for a milky appearance. Coolant can mix with the motor oil if the head gasket leaks, if the head is warped or cracked, or if the block is cracked. Also check for oil mixed with the coolant.

- The positive crankcase ventilation (PCV) valve is clogged

- One or more piston rings is leaking, allowing excessive blowby in the crankcase.

That is usually a sign of water in the crankcase. Check and or change the pcv valve, check dipstick for water emulsified oil (white or light colored oil), if detected, change oil and filter. Do you drive your vehicle only a short distance at a time not allowing it to reach normal operating temperature? That can be a cause, or something much worse I'm afraid. IMHO.

Ray, on a Saturday night, giving auto advice, we have no life. I'm going for a gin and tonic.

(RAISES HAND EXCITEDLY BEFORE RAY THE CLASS SWOT DOES) Ooh, yesyesyesyesyesI know this one! Water in the oil? Leak between engine cooling water and lube channels? Bad head gasket (or, as in my Vauxhall Chevette (UK model, circa 1976), a warped head)?

Do I get a Gold Star?

Thanks everyone for the suggestions. My child is driving this car to school everyday for couple of miles, that's probably the cause. The coolant is not disappearing. So it's probably less likely it's leaking into oil, but I'll keep an eye on that. I also checked the PCV and it's not clogged.I'm not using any additive either.

Is there any way to prevent this (other than changing driving habits, :))? Guess I could switching cars with him from time to time. But I really don't want him to drive the new car, you know, :).

LOL! Kinda sad, huh. Tomorrow will be busy - brake jobs on the Sequoia and Avalon, brake fluid flush on the Avalon, coach daughter's soccer game, and dinner at #1 son's house for his birthday.

Yes, now, sit DOWN, Andrew!

Oooooh....Screw that! I'm going to bed EARLY!

A drummer from one band I'm in called me up...an Open Mic on Thursday, the regular drummer broke his hand. Ok, I'll go for a couple hours...his wife, our singer stops in...played for about 90 minutes or so, two Crown and Cokes and a Guiness, and a dozen songs later, I stumbled in at 12:45...

Friday...nothing to do...I'm going to bed EARLY! 8:35...hey, the bass player can't come, wanna sit in...uh..SURE! The place thinned out around

12:00 so we played until 12:30...a Crown and Coke, a Long Island Iced Tea, a Guiness and a double shot on Ouzo later...

Then, practice with the other band today...no drinks...

tomorrow...nothing...THANK GOD!!!

Sure do!

I change oil at around 3000 miles and occationally take a drive of 10-20 miles down the freeway at speed with OD off to get the engine revs up and warm things. Most of my normal driving is stop and go city type slow speed, 45 MPH ect.. 04 Sienna.

Most likely is coolant in the oil. Simple test is pull the dip stick on a hot engine, and drip some on the exhause manifold. Just oil will smoke, any coolant /water will bubble. If so, you have a head gasket on the way out. For a 1990, this means polling the head off and getting it reconned (valve lap, check all valve guide, new stem seals and surface grind).

SD

As has been said there a several possible causes. I had the problem with a 63 Chev II that had piston ring blow by. A ring job cleared up the problem.