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I checked my oil level today and decided to top it up with around half a litre.
When I removed the oil filler cap I noticed some white gunge in the filler cap and some froth down the filler tube itself.
Years ago I remember this actually meant something but I've completely forgot.
Any ideas?

I'm guessing it won't be anything good

I might be wrong but , I think that generally means you have water in your oil!
Not a good mixture I am lead to believe.
Hopefully just a head gasket maybe?
Or possibly blown/distorted head, hopefully and probably not.

Gordon,

It's generally agreed that white gunge is caused by water mixing with oil and, therefore, typical of head gasket failure. However, you can get moisture caused by rapid cool-down of an engine. For example if you've done a recent number of short journeys after the car has been started from cold. Does this sound likley? Try cleaning out as much of the gunge as you can and do a couple of long runs. You might find the problem has gone!

If unfortunately you have got head problems and you've got water coming from the cooling system, you might also have oil getting into the coolant. Take off the header cap (when the engine is cold) and see if you've got a rainbow-like effect on the surface of the coolant, which indicates oil contamination. Also, try starting the engine with the cap removed and see if you get small bubbles rising to the surface of the coolant soon after starting, as the head gasket leaks allows pressurisation of the coolant.

Good luck, Gordon, let's hope it's not bad news.

Paul

I usually do trips of 15 miles at a time for work (main roads out of town), but have to admit yesterday I did a lot of small trips of say 1 or 2 miles around town running errands.
Maybe this set it off?
However last summer the car was using water and I never did find out where it was going too. (about a pint every 1,000 miles) but this has now stopped for good.
Thanks for the info guys I'll check the water and the oil filler during the week.

Fingers crossed!!

Gordon

I had the mayonnaise problem on both my present and previous XJSs. The latter right after a head gasket job. In my case the 12 mile trip to and from work was definitely the cause, the oil didn't make temperature for about 20 minutes. Condensation would form in the filler neck and associated pipework and wasn't being driven off.

You may find that if enough of this goo accumulates it can actually migrate as far as the elbow from the airflow meter. I had to take the pipes off and clean them with paper towel.

Now the car only tends to come out for long journeys the problem has gone away.

Cleaned out the gunk and started her up first thing this morning to see if there was any oil on top of the water and to see if any bubbles appeared in the header tank.
All OK up to now.

Went for a trip out of town today as well and had a look in the oil filler before the return journey and seems to be OK up to now.

I think I'm going to monitor the situation for a bit longer though

Gordon

"I think I'm going to monitor the situation for a bit longer though"

Good Thinking

My 3.6 used to develop a bit of mayonaise in the oil filler neck, especially in the winter and it never had any head (or other) engine problems. So I would definately monitor and let it develop for the moment.

If it really bugs you buy one of those spiral wrap on twisted wire nylon alloy wheel cleaners and screw it down into the oil filler neck and then withdraw it, still screwing it (clockwise?) - it will remove all the gunge and you will have a clean filler neck to monitor! Beware that the bristle diameter is not TOO great or it may become a little jammed............. (Local South Glos. Bodge)

Regards

DH Dove

Well up to now all seems to be well but after almcl mentioned the mayonise migrating as far down as the air flow meter I decided to take the air pipe leading to this off mine and have a look.
Below are some photos!

http://www.razey.karoo.net/images/gunge.1.jpg

http://www.razey.karoo.net/images/gunge.2.jpg

All clean and back to normal now