Slight foam or rust on oil dipstick? Try an o-ring.

[SkyVolvo]

Seeing a bit of foam on your dipstick can be terrifying - more than once I've jumped to the conclusion that I had blown a headgasket, when in fact I had no problems at all. I also wasn't making the short trips that sometimes cause condensation to collect on the dipstick though, so I wasn't sure what was causing it.

In addition to the foam, there was a rusty-colored grossness near the top of the dipstick, so I figured it wasn't sealing correctly. I bought a replacement o-ring for a few cents from FCP the next time I placed an order, and replaced the petrified original one on the dipstick. No more foam, no more grossness, no more sudden heart palpitations at the fear of a blown headgasket.

[jblackburn]

Aren't the simple fixes the best?

[pa cockle]

1..are the O rings there to keep pressure in or air out..
2..what are the ramifications of fitting the old style cup to the dipstick (held in by gravity alone) and eliminating the seals.
3..What would be the first car component to suffer,eg Rings or bearings or gaskets?

[dbbotkin]

The crankcase has a negative pressure (vacuum) under normal conditions: the O-rings prevent air from entering. If the PCV system is not working properly, a pressure is created in the crankcase. This is not a good thing because it puts pressure on the crankshaft and camshaft seals. The result is likely the blown seal somewhere and a bad oil leak.

It is normal for there to be some moisture in the crankcase when the vehicle is driven only short distances, particularly cold weather. Moisture plus oil plus agitation equals "whipped cream" or in this case, foam on the dipstick.

[kcodyjr]

Note that a new o-ring might not help much, or for long, on the older one-ring dipsticks.

I haven't seen it come back in a year after swapping the tube and stick for the new style.