engine oil mayonase

Post by **dalebrignall** » Sat Mar 01, 2008 6:47 pm

hi i changed the oil a couple of weeks ago. i was running on duckhams,wich did make a bit of gunk on the rocker cover. i have put some commer premioum 20/50 and it seems worse. i am not losing or useing any coollant is it just the time of year car not getting hot enough running at 70/80 celcious

Post by **Orkney** » Sat Mar 01, 2008 6:52 pm

Sounds strange? wouldnt have thought condensation would be causing it - but doesnt take a lot of water to cause the emulsifying, youd notice it in the oil if you only had a tablespoon of water in there.
maybe a flush might be an idea? could be youve got some mayo lodged in a throughway thats on its way to clearing?

Post by **MoggyTech** » Sat Mar 01, 2008 7:08 pm

Which crankcase breather system do you have? Cars with the rocker cover to air filter breather seem to be more prone to this. Cars with the breather taken from the tappet cover to vacuum side of carb, seem to get it less often.

Make sure correct oil filler cap is fitted. Vented for tappet cover type breathing. Sealed for Rocker cover to air filter breathing. If vented type, clean out or replace the mess filter in the cap.

Whatever type of breather system is fitted, ensure it is not blocked in any way.

Post by **Judge** » Sat Mar 01, 2008 7:37 pm

You might be very surprised at just how much 'mayonaise' can be caused by using a car for short trips, particularly during cold weather.

Post by **dalebrignall** » Sat Mar 01, 2008 7:48 pm

the breathing system is rocker cover to air filter. i am going to brooklands next weekend so ill give it a good blast round the 25 for a few miles to see if that evaporates out.i dont get this in the summer months when its warmer.i have not used an engine flush on this engine,its done about 5000 miles ill give it a try

Post by **Alec** » Sun Mar 02, 2008 7:36 am

Hello Dale,

yes you do get mayonnaise on cars that are not getting a lot of running.
What can happen if you then do a long run is your oil level will drop due to boiling off the water in the oil, so it's worth keeping a check on it.

Alec

Post by **alex_holden** » Sun Mar 02, 2008 10:39 am

What thermostat do you have? I've got an 88C one in it at the moment and it runs at about 88-90 once it's warmed up properly. I do still get some mayonnaise in the cap though, probably due to the relatively short daily commute.

Post by **bmcecosse** » Sun Mar 02, 2008 10:52 am

This is always caused by short runs - and inadequate engine breathing. I suggest you carefully clean the pipe from rocker cover to air filter - it may be blocked with gunge!

Post by **Willie** » Sun Mar 02, 2008 11:43 am

The Minor is prone to producing mayonnaise even leading to suggestions about mods to prevent it. With two identical Minors which I owned at the same time one would always produce it whilst the other never did despite there being no apparent differences in use. A good high speed blast at regular intervals will usually blow it through. Fortunately,on the Minor it does not usually suggest a blown head gasket which it does on other cars.

Post by **RogerRust** » Tue Mar 04, 2008 10:25 am

I will probably be shot down again, but I think that if you have a vented cap and the 1098 type breather. You get less of a problem than with an un-vented cap as per the 948. In my simple mind the venting is going from the top down in the 1098 and from the bottom up on the 948 so all those moist gasses from the combustion process end up in the rocker box where it is cooler and therefore condense to give the mayonnaise that we often see.

Before I go to the bother of finding a 1098 tappet cover vent and a rockerbox without a vent pipe I'd like to know what other peoples experience is. The question is which is better tappet cover to carburettor or rocker cover to carburetor?

As an aside please see previous posting on this subject.
http://www.mmoc.org.uk/index.php?name=P ... ic&t=18298

Post by **alex_holden** » Tue Mar 04, 2008 12:20 pm

RogerRust wrote:I will probably be shot down again, but I think that if you have a vented cap and the 1098 type breather. You get less of a problem than with an un-vented cap as per the 948.

Incidentally Fenchurch is one of the earliest 1098s and it has the breather pipe from the rocker cover to the air filter housing (and it does have a slight mayonnaise problem).

Post by **MoggyTech** » Tue Mar 04, 2008 1:52 pm

The question is which is better tappet cover to carburettor or rocker cover to carburetor?

Tappet cover to carb everytime.

Post by **bmcecosse** » Tue Mar 04, 2008 2:47 pm

Rocker cover to carb - far better than into the filter which just smothers it in oil fume and blocks the paper element! Breathing from the rocker cover keeps the moisture content in there down - it's the 'coolest' part of the engine.

Post by **Willie** » Tue Mar 04, 2008 7:07 pm

ROGERRUST, the mod I mentioned was a made up deflector plate designed to deflect the incoming air from hitting the rocker box and cooling it which was undesirable. I made up this mod on the Minor I had which always produced mayonnaise. It made no difference whatsover and was a waste of time. I used this minor as my everyday car for ten years with no attention ever needed to the engine

Post by **dalebrignall** » Mon Mar 10, 2008 5:41 pm

finally got rid of the mayo in the rocker cover.it was still there when i went to brooklands.got the car home left it on the drive with the engine running.had a cup of tea drove it back to the lock up mayo gone.i recon it got hot enough on the drive to evap it off

Post by **alanworland** » Mon Mar 10, 2008 8:40 pm

Keep it hot and the mayo will be minimised.