Oil fill cap/temperature question

[APXD 30]

Over the weekend, I checked fluids & tire pressures on my cars.    The GTI was half a quart low (not unusual for this car).   When I removed the filler cap, I found what I can only describe as a 1/4-1/2 inch dried foam on the bottom of the cap.   It was a sand colored substance.    The car hadn't been driven long this weekend but moved around once or twice.

The dealer said, over the phone, that this wasn't a big deal and that it was the sign of a hot engine cooling rapidly with the low temperatures.  They didn't see a reason for bringing it in.   The Audi was not this way but had been driven about an hour before checking it.

Obviously, I will keep an eye on it and take a picture of it next time.   Maybe I'm hypersensitive b/c my A4 1.8T had the sludge problem on the first engine.

Any thoughts from someone who might know more about these things would be appreciated.

[michael lang]

Josh, I wouldn't worry about it too much. It's more of a condensation issue than anything. We see that with some of the Benz's here at the shop. One thing that we have added to our service menu on the A or B maintenances is a BG kit which appears to be helping. I can't really comment on what the VW dealer told you. If you're not experiencing any drivability issues and it's not using an excessive amount of oil than  what's considered normal, you probably have nothing to worry about. If it really bothers you, try a couple of oil changes along with an oil additive between now and your next scheduled maintenance. Either route, I believe you'll be fine.

[JoeP]

Back in The Day, I worked a Summer for Mobil in their engine testing lab.  Foam or jelly in the cooler parts of the engine can occur during the winter if you do not get the engine to full operating temperature for 20 minutes or so.  It is a common problem for people who only use their cars to go to the train station.

Water condenses in every engine when it gets cold and mixes physically (not chemically) with oil on the upper parts of the engine.  Extended operation boils the water away, and no damage occurs.    This usually is not a significant problem in the sump that supplies the oil pump.

However, upper-engine gunk can build up after repeated short starts in very cold weather.  It can cause long term trouble if foam progresses to the point where it mixes with crankcase oil and water gets pumped into the bearings. 

Oh, if the foam/jelly smells sweet or looks yellow, the water could be coming from a coolant leak in a water cooled engine.  Look for oil in the radiator.

[APXD 30]

Thanks guys.  You put my mind at ease.   Jenn does have a short commute to work so it sounds like that, along with the cold weather, may be the culprit.

I've see the antifreeze issue along time ago with a bad head gasket (Jeep 2.5L).   This wasn't the slime but more foam/jelly you mentioned.

I think I might have to drive her car from time to time on longer trips and try an additive during the winter.

[APXD 30]

I checked again today, not dried this time....looks like sludge to me.  Radiator fluid bright red, not oil whatsoever.   Car has been driven a little further than usual since last post (at least one long 100+ trip/week).

 Any thoughts before I take her to the dealer?   

[michael lang]

Josh, has anything changed? Are you still experiencing the foam on the oil cap?

[APXD 30]

Michael,

We're in good shape now as it has been a few weeks and no return of the incident.   Thanks to your offline assistance, I've treated the oil and gas system with the BG Products you sent me.   Also, when I changed the oil, I  switched from Mobile 1 to Castrol Syntech.

I considered Royal Purple (surprisingly available at Wal-Mart and not my local parts retailer), but I couldn't find it in 0W-40 the day I changed the oil.

Thanks again for your advice with this!

[Larry Herman]

Years ago someone wrote into Pano asking about "Motor Mayonaise".  He was referring to the creamy goo that you are seeing on your oil cap.  As already stated, it is due to condensation causing the oil to foam and get whipped inot a froth, like mayonaise.  Some oils are more susceptable to this than others.