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Why would Auto Oil turn into yellow sludge?

kookbreaker

Evil Fokker
kookbreaker
Joined
Aug 23, 2001
Messages
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OK, odd science problem here. My car has ahd an oil change lately, and the past couple of times the oil changer has pointed out that the cap had a yellow sludge on it. From what I don't know. I had them do an engine purge. Fast foward a little bit, I was checking my oil today and found that the cap, the pipe leading to the oil resevoir and the dipstick all hav the same yellow sludge. I am using synthetic oil and my car is a 2000 VW Golf if that matters at all.
 
Water in the crankcase. If you're lucky it is condensation. If you're less lucky it could be a torn head gasket. If you're luckless it could be a cracked block or head. Good luck...
 
It's moisture in the oil making a frothy emulsion, could be condensation or it could be a leaky head gasket.

Are you losing antifreeze?
 
I don't think I am losing antifreeze. The pan was leaking before and had to be replaced, and I am not certain they did the job right (my last oil change required a top-off return trip, and it is synthetic oil). Could water be getting in from there?
 
Sludge is an inevitbality of synthetic oils. This article is quite helpful and suggests changing the oil at appropriate intervals.
 
If you're in a cold climate, when you shut off your engine water condenses inside the cylinders. This is the foundation of that sludge (I worked at a quick-lube place many moons ago). I'm guessing your commutes are fairly short? Over a longer drive, this moisture should evaporate and be released by the crankcase ventilation system. If you don't have a cracked head (no offense :)) or a torn head gasket, try replacing your PCV valve, maybe $3, and take a good, long drive to get the engine up to temp for a while. IMO, they bent you over doing that engine 'purge'.

(ETA) Using synthetic is a good idea, but you'll see the same sludge-y buildup using conventional oil, take my word for it.
 
Yellow oil (synthetic or otherwise) is water as the first poster said.

If you drive it a while on the freeway (until the oil temperature gets up as well as the water temperature, at least an hour) and it's still yellow, you have a serious problem and need to find out where the water is coming from.

If you see ANY hint of oil pressure or operation issues, STOP. STOP STOP STOP.

It is possible, but only just, to create this problem with condensation with consistant short-drive usage that never gets things warmed up. That's bad for your car in lots of ways, btw.
 
My commutes are very short. 12 miles to work and 12 miles back, so that fits. I'll have to resist their selling of the purges, since they seem to do more harm than good. I have had no signs of oil pressure problems, though.

I can't really do too much about it. My commutes are short. Back in the day, when I was driving the museum cars I would drive them 2 hours there and 2 hours back all the time. But that is not what I do anymore.
 
Once, when working on an old Ford Pinto I used to own, I managed to crack the head gasket between a coolant channel and a cylinder. Within about 3 miles, the contents of the oil pan had turned into something almost exactly the colour and consistency of chocolate mousse.

Cleaning that out was one of my least favorite auto repair jobs, ever.
 
Old mechanic that I am, I'd say to get your crankcase ventilation system checked out. 12 miles ought to be far enough to get things up to temp, but without good flow through ventilation the vapors won't get pulled out. Stuff like PCV valve, filter, plugged hoses.....
 
casebro said:
Old mechanic that I am, I'd say to get your crankcase ventilation system checked out. 12 miles ought to be far enough to get things up to temp, but without good flow through ventilation the vapors won't get pulled out. Stuff like PCV valve, filter, plugged hoses.....
Click to expand...

Agreed 100% with casebro.

12 miles each way might collect a bit of moisture, but not very much, and certainly not enough to be strikingly obvious.
 
kookbreaker said:
OK, odd science problem here. My car has ahd an oil change lately, and the past couple of times the oil changer has pointed out that the cap had a yellow sludge on it. From what I don't know. I had them do an engine purge. Fast foward a little bit, I was checking my oil today and found that the cap, the pipe leading to the oil resevoir and the dipstick all hav the same yellow sludge. I am using synthetic oil and my car is a 2000 VW Golf if that matters at all.
Click to expand...
I think you've received some pretty good advice here from others.

I'll add to that the recommendation that you do some digging to see if any applicable make/model/year-specific information might be available. There are some fairly supportive on-line communities based on enthusiasm for different sorts of cars, and I imagine that this would apply to VW as well. It's often the case that certain specific issues with particular cars, engines, transmissions, etc. are very well known in such communities.

Search before posting a question. If you can't find anything, it's usually a good policy to preface the question with something like, "OK, I've searched the archives for information on (yellow sludge, goo, whatever), and I couldn't turn up anything..."

I did a little searching at http://forums.vwvortex.com, and saw some posts describing observations very similar to yours. In some cases, suggestions were offered regarding specific things for which to check - possibly cracked dipstick tubes, leaky seals on oil filler caps, etc.
 
In my experience, VeeDubs and Hondas seemed to show this more than other makes.
 
Water + oil + mix = yellowish emulsion

I know this was said a bamillion times already, but I'd just thought I'd say my peace. My old job involved testing oils in different ways and the emulsion test was one.

Tests have been performed in a lab. Skeptical feelings may be put to rest. :D
 
I have just a five mile trip to work, so I make an effort to drive my car for longer periods once in a while to avoid condensation/sludge trouble. Once in a while I just take a really long route to get everything up to temperature for a while.

12 miles should really be enough though, I would think.

Maybe you could start taking a bit longer trip each weekend?
 
KingMerv00 said:
Water + oil + mix = yellowish emulsion

I know this was said a bamillion times already, but I'd just thought I'd say my peace. My old job involved testing oils in different ways and the emulsion test was one.

Tests have been performed in a lab. Skeptical feelings may be put to rest. :D
Click to expand...

Oh, indeed, I'm quite confident of what it means, myself, having seen the experiment made by at least a half-dozen head gaskets, a couple of cracked heads, a busted GM intake manifold or three :)
 
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