oil full of tiny bubbles

[archiboy24]

Hey guys,

I am near completion of my 3B Coupe Quattro conversion, but I seem to have run into an odd problem. The low-mileage donor engine was completely torn down (except crank and pistons) and refreshed with new seals, gaskets, hoses, etc., including a metal head gasket and urS4 windage tray. This past weekend - after sorting out a hall sender problem - I fired it up for the first time since completing its installation in the coupe. It started up first crank and settled nicley into a steady idle. However, almost immediately, the oil pressure warning light came on in the Autocheck. I shut it down and checked the oil, knowing it would be ok because I just filled it! But the oil was a little strange. It was kind of thick and frothy and looking closely at it, it was full of tiny air bubbles. Now this is different than the way oil looks when a head gasket has blown. It's not milky or creamy, just thick and a little frothy. A couple of other bits of background info: the temperature at start-up was about -5 degrees celcius. When I filled the oil, I poured in 4L, however, the dipstick read that it was slightly over-full, even though oil capacity is 4.5L with filter. I figured this would read correctly once the oil circulated through.
So, my questions are, does anyone know what can cause these air bubbles? Has anyone experienced this before? Should I be concerned? What sort of things should I check? Could this have triggered the oil pressure warning?

Thanks in advance!

Ben

[dan_b]

I heard a story once about a chap with an Alfa Romeo which broke down. They had to strip the engine down in the end to work out why the engine was being starved of oil, to find a pair of workman's overalls in the sump...

I know that doesn't help you, but maybe, just maybe

[Glen Chamberlain]

I once put a head on an old 1.8 80 and mistakenly turned the intermiediate shaft backwards. When i reassembled it it started fine but the oil pressure light stayed on and the engine sounded dry! What had happend is i had empted the oil pump and it had "air locked". It was my mates motor so he decided to rev it one to see if he could get the pump spinning quick enough to self bleed but no. Had to remove the oil pump and prime it, reassembled, and everything was ok! Just wondering if you have a similar problem?

Maybe an option is to fit an oil pressure guage and remove the plugs (to minimise load) and crank it over and see if you can get it to clear and/or see what pressure is being produced? Dont burn the start out mind!!

Risky i know, lack of oil pressure is diffcult to work with cos of obvious reasons!

Good luck with it! Maybe someone else can give you a magic answer!!

[porkkis]

Take the plugs and fuel relay out and crank the engine and see what happens. The pressure should rise to about 4 bars just with that.

Bubbles could mean your oil suction pipe seal leaks at the pump end. It's higher than the oil level.

Amount could be explained with a empty oil cooler. I suggest you pre fill it. Otherwise you might have a bearing failure when the oil temp rises and the oil cooler thermostat opens when the engine is under load.

[A6 AVANT]

Check your filter to make sure it is receiving oil and make sure your relief valve is free. Also is your pick up gauze clear?
With the filter, the old RangeRover V8 used to have feed problems and we always half filled the filter prior to fitting to give it a chance to bleed.
Oil problems are tricky one's to sort Don't envy you this one!
When cranking, remove filler cap and see if you see oil at the cam.
Good luck and let us know

[archiboy24]

checked my oil again last night...

Good news! The oil looked completely normal again. No longer frothy or full of bubbles. The other thing is, the dipstick now reads down a half litre, as opposed to over filled by half litre before I started it. This makes sense, since I only filled 4 of its 4.5L capacity. So in the end, I guess what happened is that every drop of oil that I had poured in was sitting in the pan. This caused an over-fill situation, causing the crank shaft to whip the excess oil into a thick foam.
As for the oil pressure warning light, I'm not sure. I haven't had the chance to look into it. But given that the oil pressure gauge reads normal, and that it appears that the oil has circulated to its proper places, I have a feeling that the wires on the sender may be reversed. I won't be taking that lightly though.

Thanks to all of you who offered insight!

[dan_b]

no overalls in the sump then?