mayonnaise!!!

[tom]

I\'ve got an 95m FD and recently since we\'ve had this cold weather i\'ve noticed sometimes the smallest bit off mayonnaise (oil and water mixed) in the oil filler cap! i change my oil every chance i get and thats oil filter too, normally every thousand miles! the cars never flooded or let me down once so i asume its a healthy engine but after havin bad experiences with piston engines and mayo its always on the back of my mind!
could it be just condensation?
or should i panic?
theres never any on the dipstick or in the filter when i change it!:confused:

[J4P RX]

I think itll be ok and just the weather.  A few months back there were several threads like this just as it started getting cold.

Cheers
Lee

[Fishy]

Tommy you got it right, its most likely condensation.

The build up is normally due to not being driving hard. Build up is quicker when just normal driving around town.

Dan

[StreetPizza]

I wouldn\'t worry about it, I\'m having the same problem on my Peugeot right now, and that had the head gasket changed just a few thousand miles ago. It\'s just the weather. Short trips seem to be especially bad for \'mayonnaise\' build up. I think it\'s the repeated heating/cooling of the engine that causes it.

[brooksie]

so is the answer to any mayo on the filler cap to give the car a good thrash then

[tom]

i dunno mate cos i thrash the nuts off mine everytime i use it!:D

[JimboRX-7]

Just for some further reassurance, my RX-7 has mayonnaise in the oil filler cap, my peugeot has mayonnaise in the oil cap, and my mates Alfa\'s oil cap looks like a jar of Helmans.  We both do a lot of short journeys, which may add to the effect?

[Martiny]

OK, here goes...

When there is blow by (Gasses leaking past the seals) it gets pumped into the sump, right?  Same on a boinger. The pressure in the sump, therefore rises and falls, so we need to have a vent pipe. This used be a little black rubber pipe, just venting to the atmosphere.

Then the Greenies decided that we should send these gases through the combustion chamber so they get burnt. Ok, so now we have a rubber pipe going to the intake manifold, rather to the ozone! (still with me?)

Now, lets say the manifold is under boost coz your Turbo is pumping, that little pipe would now be pressurising the sump! So there is a little one way valve, called a check valve. The air can go from the sump to the manifold, but not the other way round.
(still with me?)

I think that the sump never see any fresh air, and therefore condensation builds up, forms little droplets on the oil cap, mixed with oil and, hey presto - Mayonnaise.

I wonder if it would go away if we left to oil cap off every time we stopped? ( NOT recommended - you\'re bound to forget it one day, and then Mayonnaise will be the least of your worries)

The above is all speculation on my part, please shoot down my theory/s if I\'m  talking bullshavings again!

[tom]

sounds bloody good to me!
i\'d rather that theory than someone tell me i need a rebuild!!
cheers!:wave