Thick black sludge in oil

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T25Convert
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Thick black sludge in oil

Post by T25Convert »

Hi all,

Not the van this one, but a 1971 beetle (my other car) - asking on here as the beetle forums seem pretty clueless on mechanicals...

Changed the oil last night for the first time in my ownership, and it had a good half inch of thick black sludge at the base of the filter plate. At first it seemed gritty, but it rubbed down to nothing in my fingers. Genuinely rancid stinking stuff.

So, it was well overdue a change, but what is this sludge? Never seen anything like it.

Would people recommend any flush products, or simply change the oil in a couple hundred miles to flush out any other bits that are floating around?

Cheers all,

Alex
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Re: Thick black sludge in oil

Post by CovKid »

Its likely that in the past, only the drain plug was removed and therefore strainer built up gunge. As theres no filter really in a bug, all the thick deposits settle on bottom of crankcase. You COULD flush it if its that grimey (think I would). Not sure best way in your case as you need to break up that thick layer (leave flushing agent in crankcase overnight to dilute it?) then drain again. Few oil changes after that should remove it all.
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T25Convert
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Re: Thick black sludge in oil

Post by T25Convert »

CovKid wrote:Its likely that in the past, only the drain plug was removed and therefore strainer built up gunge.

That was my reading of the situation - glad I caught it though as the sludge was going to totally block oil flow in the not too distant future. Worryingly it was owned by a professional mechanic for three years before me, makes me wonder what else he didn't bother doing!

It has the requisite 2.5l of oil back in it now, so will run this through for a couple hundred miles, then flush and refill.

Amazing how crusty oil can get!

Cheers,

Alex
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Re: Thick black sludge in oil

Post by bigherb »

As Cov says a lack of maintenance, also using a SAE 30 mono grade oil that was not a HD (high detergent) oil. As there is no oil filter the HD oil is supposed to hold the crap in suspension until it is drained at 3000 miles intervals or yearly whichever occurs first.
Has it got a G as the middle registration letter? I might have done the PDI and worked on it when it was new.
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T25Convert
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Re: Thick black sludge in oil

Post by T25Convert »

bigherb wrote:Has it got a G as the middle registration letter? I might have done the PDI and worked on it when it was new.

Nope, this one has an 'N' as the middle letter, previously had one with a 'B'.

Last beetle I had didn't have a drain plug, so you were forced to take the mesh 'filter' out every change just to get the oil out. This one though has all mod-cons and is complete with drain plug, but seems this led to sloppy maintenance. Tonight's job is tappet check and grease front beam as I suspect these may also have been 'overlooked'.

Forgotten what a pain it is getting under a car - used to the van now that I don't have to jack up!!

Cheers,

Alex
RIP - George - 1.9DG '85 AutoSleeper Trident - rusted away

George Second - 1.9DG '89 Caravelle

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Re: Thick black sludge in oil

Post by mark »

don't flush it...............you'll kill it. take the strainer out and clean it with petrol, soak the rest and clean. put some cheap oil in it run it to warm and drop it, repeat until you loose the silvery haze.

only a word of warning, been there done it and paid the price

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T25Convert
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Re: Thick black sludge in oil

Post by T25Convert »

Mark,

Thanks for the warning, I will abstain from the flush then!

Cheers,

Alex
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Re: Thick black sludge in oil

Post by bigherb »

Yes defiantly don't flush it. Use a good SAE HD30 oil (Comma do one easily available). Run it for 500 miles then change again. If you want to use a multi grade then use one for Diesel engines.
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Re: Thick black sludge in oil

Post by CovKid »

Aye, no harm in using a diesel oil. Its detergent properties should help break up the crud and a few runs through with fresh oil changes should remove whats left. I used Shell Rimula for quite a few years in a bug but to keep your costs down, alternate with cans of low-cost LIDL brand as they're about a tenner a can and a good multigrade without the hefty price tag.
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Re: Thick black sludge in oil

Post by Theclash »

Not up on beetles or air cooled but if it was me I would also be dropping the sump and cleaning in there

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Re: Thick black sludge in oil

Post by CovKid »

Theres no sump to drop. Just the strainer plate and theres no access inside due to oil pickup pipe.

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