Checking my oil yesterday I saw some brown foam-like stuff on the dipstick. I have noticed this on other cars in the past. Is it caused by water in the oil or possibly condensation in the sump? Is it a warning of impending trouble? Any thoughts are appreciated.
RagJag

 

A white-ish mousse like gunk is evidence of coolant in the oil. Worst case is you could have a head gasket on the way out. Usually it appears on the oil filler cap, and on the cam cover interiors.

I suggest you give the car a good hours fast run and then see what evidence there is of any foamy mousse anywhere you can look.

Greg

 

As Greg says, foaming of the oil is not unheard-of, and is generally caused by condensation or, occasionally, a bad head-gasket. The fact that you describe it as "brown" makes me ask - I suppose the engine isn't over-full of oil, which is getting "churned" and foamed by the crankshaft dipping into it??

 

if it looks like coffee, its probably water. ive never seen the classic "white milky" stuff after ive gotten coolant in the oil. it always looks like coffee to me. other things will cause it to foam up as well including things like the oil being overfilled causing it to be churned up by the crank, or on an engine that lacks a windage tray, you can get some foam after a WOT pull or some hard corners.

 

AJ16 engines such as yours are not known for blowing head gaskets, even in higher mileage examples, but it does occasionally happen.

What is common is a condensation on the oil dipstick tube (cant remember why) Look in the X300 (same engine as yours) archives and you will see what I am talking about .

Good luck

 

Thanks to all. I am hoping it is condensatoion because it hasn't been there all this summer but now we have had some cool nights. The sump is not over filled. I changed the oil in July and all was well since then. It may be short runs around town with the coolant barely getting up to full temp. I will monitor it and hope it isn't too serious.
RagJag

 

The weather is cooler and condensation in the engine more common after short runs where the engine doesn't get hot enough long enough to evaporate (proper word?) all of the water vapor in the engine. My XJS diven daily 50 miles doesn't have the goo, whereas my VDP does because of the short trips it's used for. Watch the coolant level in the overflow tank for disappearing coolant. My guess is that you're using your car for short trips in cool weather.

 

Same here, always in cooler months this happens.

Was mighty worried the first time I saw it.

Also happens in the older models with an Oil Fill tube, remove the cap and see mayonnaise.

 

I had an XJ40 with the AJ6 engine, never any problems and always ran like a dream but the dipstick went rusty for some reason.
You'd figure that being dipped in oil would prevent that.
Steve

 

Roger95, exactly right, I do take short runs in the XJS.
RagJag

 

You should take for some good hot runs and burn all of that crap out.
I do that with the VDP at least once a week.