Engine oil removal through diptube and others....

[Deltona]

Why?

A few newish European cars now have no sump plug and the oil is sucked out of the dip tube when changing it, I can't think of a more stupid idea, but there must be a reason for it, anyone any ideas?*

I like to look at how things are done on new cars when I get chance (incase there are things to be learned and applied to my own older car), but I just can't get my head around some of the weird things I see sometimes - I had a look at the intake manifold that was removed from a VW turbo diesel, the inlet was at one end, it ran along, did a U-turn, back the other way, another U-turn then went into the plenum, but why? Why make the air go further and round more flow losing U-bends? Noise reduction perhaps?

*It would be too easy to say it is to thwart any keen DIYers as hardly any 'normal' people get their hands dirty these days and for those that want to the tools to do the job are readily available....

Any additions or answers appreaciated.

 

[ivymike]

How does all that lovely sediment in the sump get sucked up?

same way it always does - the oil pump intake tube draws it in and the pump sends it to the filter, where the particles are trapped.

another reason to change your oil while "hot" is that the particles are more likely to be suspended vs deposited.

 

[evelrod]

Actually, Isaac, you have correctly stated the theory of the dip stick oil change. I don't remember the first time I heard about this method, but I had a neighbor many years ago that had a small mechanical pump and changed his oil regularly with it. Years later he wanted to upgrade to bigger, better, faster...whatever and he needed my advice on how to clean the "gunk" from the oil pan. To my amazement, the sludge had built up to about a half inch and was hard enough we had to use a gasket scraper and sand blaster to get it cleaned out. My guess, therefore, is that "...all that lovely sediment in the sump (does not always) get sucked up"!

Rod

 

[ivymike]

perhaps I should clarify (although it may be clear from context) - I was referring to the engine oil pump, not an external oil change pump.

I would have said "what's the sludge matter, as long as it stays put" but I'm aware of at least one example where accumulated sludge (at the end of a crankshaft drilling) came loose and relocated to a less-benign position, resulting in engine failure.

That sounds like a pretty extreme case, Rod. Do you think a modern commuter car with modern lubricants produces/accumulates that much "sludge?" What's the "sludge" made out of, anyway? Soot+oil?

 

[evelrod]

"What's the sludge made of...."?

Good question, Isaac. I don't really know. If memory serves (and, of course it usually does not), the gunk was more like a thick layer of varnish. Quite hard with a black, sludgy, gooey stuff on top.

Rod

 

[patprimmer]

As far as crankcase deposits goes:-

I would call black lumpy deposits carbon. They build up on very hot surfaces like parts of pistons and where oil splashes on exhaust ports. I think they are oil decomposed to the point that they are pretty much carbon.

I would call golden to black thin shiny deposits varnish. this normally builds up in very tin areas that get hot, but due o space get worn and polished. I think this is a mixture of oil molecules that have cross linked and some small particles of carbon from decomposed oil. They are thin and shiny mainly due to polishing action. The cross linked oil is the result of enough heat to start some degradation, but not enough heat to fully degrade most of it to carbon.

I would call the grey pasty stuff that lays in corners and crevices and on the bottom of the sump sludge. I think this is a mixture of fine carbon, some degraded oil additives, some detergent, some fine metal and metal oxides and dust particles and some water.

I have seen the grey sticky toothpaste like deposits 1/2" thick on the bottom of a sump. I have seen it come loose and plug a gallery or pick up screen or both. This has always been on engines from cars that had owners not interested in cars and only use it for local shopping with no highway or high speed long trip use and were long overdue for an oil change.

The change to a new owner who changes the oil and drives longer and faster stirs the sludge up, wella, spun bearing.

Regards
Pat
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[RossABQ]

The classic grey sludge that is really nasty is in old cars that ran on leaded gas, with cool thermostats, and no PCV.

Talk to the kids at Jiffy Lube et al; they all have burns from hot oil getting up their sleeves. They are probably applauding this move.

 

[drwebb]

Well if one wants to call technical things by technical names, CRC Manual no. 20 for rating engine Sequence Test parts has formal definitions for varnish & sludge. In a nutshell, varnish deposits cannot be scraped off with a rubber spatula, and sludge deposits can.

By contrast, Shell Gasoline has apparently decided 'deposits' isn't alarming enough to attract consumer attention and so scrupulously refers to them in their marketing by the equally descriptive 'gunk'.

Sludge and varnish form from oxidized components of the oil. Oxidation makes them more polar and hence less soluble in the oil. Anti-oxidants are included in oil to prevent their formation, and dispersant ingredients are incorporated to prevent their precipitation. I think sludge tends to have water present and so tends to form at lower temperatures, while varnish is more of a high T issue, but it's not unusual for them to be observed together. I speculate there may be more cross-linked polymers in varnish, too. But the definitions are practical rather than chemical.

 

[SomptingGuy]

Back to my question...

How much of all this stuff comes out of a sump drain compared with a sump suck?

- Steve

 

[thruthefence]

Tons of airplanes flying around with 'quick drains' installed, never heard of one failing causing oil loss. I would be afraid of such on a car, because of road debris maybe knocking it off. Fram marketed some quick drains for awhile that were pretty flush to the pan, but needed an adapter to drain the oil. ( something else to lose!)

 

[catserveng]

Early in my career I worked as a mechanic on yachts, about 90% of those engines had their oil changed via the dipstick. Based on that experience, engines that were properly maintained and operated did not appear to have excessive deposits in the sump when taken down for major repairs, even though the oil had been pulled from the dipstick for regular changes.

Engines that when torn down had lots of "gunk" in the bottom of the pan usually had irregluar maintenance, lots of idle time or used fuel from Mexico.

Never really saw where doing the oil change via the dipstick caused any additional problems as long as the right equipment was used and the oil was warm when pulled. This experience is mostly based on high speed diesel engines from 35 to 1500 bhp that ran 100 to 2000 hours a year.

Hope that helps.

 

[patprimmer]

The only point I can see is it is important where the oil is drawn from, not by which method it is drawn. Whether by drain plug or suction tube, what counts is how close that point is to the bottom of the sump and how much is left behind when the process is complete. That depends on pan design and drain point placement.

For pans I have made for my boats, I run a slight trough along the bottom of the pan getting deeper at the drain point end and tend to form the pan to direct oil to that trough. At the drain point I drill a hole in the side of the pan at the trough and insert a short steel tube into the hole so it is flush with the grove and weld or braze it in place. I attach a rubber hose to the tube and run it through the transom via a skin fitting. I install a ball valve along that hose in a protected position that is also easy to access. I remove the handle of the ball valve but keep it safely stored in the boat. I also install a plug in the tube so the plug is removed from outside the transom. the plug is a type that can be removed by hand, but will seal in oil if the ball valve is left open. That way I can easily drain oil to outside the boat while it is on the trailer. No risk of spillage or accidental release into the hull or the waterway. It drains to the last drop if the oil is hot.

Regards
Pat
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[izzmus]

patprimmer said:

"Some late 80s onward Hondas and Toyotas had a plastic underbelly under the engine compartment. It had to be removed to change oil. After ten or so years of removal and replacement, the attachment points become so damaged that they cannot be refitted."

Ten years? Here where they lay down lots of salt in the wintertime, the bolts usually snap off after one or two years, to be replaced by sheetmetal screws or cable ties, assuming the undertray isn't just discarded.

I assume the reason why they still continue to use 6mm thread bolts is because the issue is isolated to this region. Vehicles that use 8mm thread bolts generally have no issue.

 

[patprimmer]

Here the bolts never fail, it's the plastic that ends up tearing away from the bolt holes that deform with time and miss handling.

Regards
Pat
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[PEW]

I look at the old oil in the drain can. I like to reassure myself that it has no lumps of metal in it or other signs of impending failure. If I was to suck up the oil through the dipstick tube, directly into a can, I couldn't do this and in any event, those lumps might still be in the sump pan.

I'm the sort who goes for lunch while the sump drains out; I don't like leaving even a drop of dirty oil in there and I take care to jack up the car so the sump plug is sitting at the low point. Hopefully, draining this way, the old oil pulls all the loose gunk and debris out with it.

PW