Deposit on Dipstick

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Cars was standing for a couple of months while I was away.

Checking the oil before starting I noticed that one side of the dipstick was the reassuring honey-colour of clean oil, but the other was dark grey.

The tissue I wiped the dipstick on has a faintly yellow-gold damp patch that I associate with clean oil, but also a slate-grey "skidmark",wiped off the dipstick, that looks metallic.

I guess there were fine metallic wear particles suspended in the oil, and the long stand has allowed them to settle out. Since the dipstick is at an angle, (i.e. not vertical) it can have an upper and a lower side. I wasn't paying enough attention to know if the upper side was the one with the sediment, though thats what I'd expect.

Is this normal (on a very old car: 1986 Daihatsu Skywing)? Havn't seen it before, but I suppose this combination of circumstances might not have occured/been noticed.

I'd have thought suspended metal would visibly discolor the oil, but I suppose the oil film on a dipstick is rather thin.

I suppose I'd better drain the oil, and maybe drop the sump and look for debris. It had an oil and filter change (Mobil Delvac MX 15/40) about 6 months ago. EDIT but had omly done about 300 miles since then. ENDEDIT) Thats a recent spec oil and, from reading, may not have enough zinc for my flat tappets

There was an intermittant tick when I first bought the car but it went away after I [censored] about with water-cleaning the cylinders, so I was tempted to call it pre-ignition. Maybe something loose just got ground away and/or lodged somewhere.
 
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The picture shows the result of wiping a magnetic pickup tool (that had been in the dipstick hole for 5 days) on a piece of printer paper.

The contrast between the (presumed ferrous) tip deposit and the relatively clean oil from the rest of the tool is, I think, quite clear.



Magnetic pickup on printer paper by ed_lithgow, on Flickr

The Question arises : Is this normal? (On such low mileage oil)

The Answer arises : I don't know.

But I'd guess not. I think I've got a problem.
 
A darker stain on the dipstick is to be expected for an engine that sits for a couple of months. The stain is from contaminants in the oil reactive with the metal on the dipstick.

How many miles on the oil?

Driving the vehicle for an extended period at full operating temperature OR changing oil and filter will remove most of the stain from the dipstick.
 
Originally Posted By: 147_Grain
A darker stain on the dipstick is to be expected for an engine that sits for a couple of months. The stain is from contaminants in the oil reactive with the metal on the dipstick.

How many miles on the oil?

Driving the vehicle for an extended period at full operating temperature OR changing oil and filter will remove most of the stain from the dipstick.


Thanks for your reply. As above, about 300 miles on the oil.

Not to be argumentative, but I don't think your diagnosis is a very good fit with my description. It wiped off easily on a paper tissue, it was probably only on the upper side of the dipstick, and the above picture strongly suggests it is suspended ferrous metal.

To me, ferrous metal in the oil suggests cam, crank or oil pump wear, probably in that order of probability.

My first suspicion was that maybe using modern "low zinc" oil (Mobil Delvac MX 15/40) had caused the cams to wear excessively, The cams don't look too bad to me, but I'm no expert. I suppose if it wears evenly/smoothly but excessively you wouldn't necessarily be able to tell until it rounded off.


Anyone care to comment on these cams?



 
Thanks. I'll cop a feel the next chance I get.

Meanwhile, here's what the sump looked like. Lots of (presumably metallic) sludge, gasket and varnish fragments. I've never had it off before, (since its a bit of a pain to remove), and it looks to me as if the radially-cut captive nut that holds the sump plug might be preventing free drainage.




Maybe the metal in the oil has gradually built up despite oil changes, in which case the wear rate might not be as high as the low oil miles last change seem to indicate.

Cleaned the sump out, New ACDelco filter and the rest of my (now a bit suspect) Mobil MX 15/40, so I'll see what happens with that. I have some rather old Mobil Special 20/50 that meets the reassuringly obsolete API SG spec, so I might try that next.
 
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Too often. Previous owners had it dealer serviced by the book, on fairly low mileage. I've changed it twice in the 18 months I've had it, on very low miles.

The last-but-one owner, however, was a surfer dude, so his maintenance may have been limited to an occaisional soak in sea water.
 
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Thanks for your reply.

No, its a timing belt. First rubber-band engine I've had, since I've deliberately avoided them before.

There is a chain driving the oil pump, and I suppose some of the wear metal could be coming from that, though it's tiny.





I thought the chain looked a bit loose, but this vid, apparently of a new one looks about the same, so perhaps its OK.

http://www.youtube.com/watch?v=lyAxH12Avmk

I think the big lumps are varnish, with a few small bits of old gasket thrown in. There were some loosely adherent sheets of varnish in the cylinder head which I hadn't wanted to disturb before, but since I had the sump off (after I'd cleaned it out) I removed them with a knife and forceps, then I washed the head down with petroil. I don't THINK much of that will have been retained in the engine after an overnight drain-down and mop-out, and it shouldn't have got into the oilways.

From the previous owners description this engine had a head gasket failure just after they bought it off the surfer dude. 3-cyl engines seem to be rather prone to them.
 
Sump was leaking where the crank pulley emerges. That's the lowest point and will get sloshed on LH turns, so I took it off again with the intention of trying some silicon sealant on the gasket, and maybe having a look at the crankshaft bearings/journals.

Had probably done about 50 miles since the last oil and filter change.

Hard to be sure but there still seems to be a lot of metal in the oil considering the low mileage. Picture below shows the result of wiping the magnetic drain plug on printer paper.



Other picture is of the sump, but its rather unclear.



next picture is of the last bit of oil from the sump drained into a bottle. Looks dark to me for such low mileage.

 
I think the goo is from the HG failure settling out. I would just clean it up and do a couple of short oil change intervals with a HD diesel oil like a 15w40 shell or chevron.
 
Thanks for your reply.

The head gasket failure is a long time ago. Not sure how long offhand, but IIRC the previous owners had it for several years.

I've got some scans of service records (in Chinese) with some translations that MIGHT allow me to give it a date, but I havn't bothered, since its a bit of a chore. It'll be many oil changes, though.

I also wouldn't have thought that a head gasket failure would be especially likely to put ferrous metal (not really "goo" as I understand the term) in the oil, hence the wish to have a look at the main/big end bearings/journals. I got the bolts off one of the mains but working under the car I couldn't get the cap off, and now rather wish I hadn't tried.


Hopefully I havn't put it too badly out of alignment.

I have been using a diesel oil (Delvac 15/40) but intend changing to old spec Mobil Special in case zinc levels are relevant.
 
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I took the oil pump off and dismantled it. Since the sprocket has to come off to dismantle the pump I ended up using a gear puller on it. Seemed to be glued on with oil varnish and took quite a lot of force to shift. Dont think I bent it. but it was becoming a concern before it let go.

Thinking about it further I seem to recall traces of what looked like RTV silicon around the sprocket bolt, and there's also something visible in the above pictures.

Perhaps the bolt had a thread - locker on it? Which raises the question - should I put some on when I re-assemble it?

I don't remember anything about it in the Daihatsu manuals I have, and Loctite etc will be hard, perhaps impossible, to find here, though I have some RTV silicone.

Bit of Googling suggests that this type of sprocket is known to come loose, at least on Porsches and Landrovers.

Description of the Landrover issue

http://www.web-rover.co.uk/nav.php?p=td5kb/oilpumpbolt

I suppose I'd better try and find some Loctite.

Pump internals seem OK, from what I can see (not that I've seen one before) and measure with feeler guages.

Casting void behind the pump body was, however, full of sludge, as were the pump body bolt-holes.

Havn't taken the bypass valve apart yet because the split pin is supposed to be a non-re-usable item, and I don't have one. Wouldn't normally worry about re-using a split pin but oil pumps make me nervous.
 
Fascinating thread!

Did you properly torque the main bolt when you put it back in? Wherever you have seen thread locker, it definitely needs it. It may be available under another brand name other than Loctite in Taiwan, look for it at fastener stores, parts jobbers, &c. A Honda dealer might have some kind of Hondabond that is a thread locker. I wager more damage was done to the engine with its dis-assembly and re-assembly than the probable non-problem of oil condition.

Mobil Delvac MX has way more zinc in it than Mobil Special, besides flat tappet wear from using oil with insufficient zinc additives would take around 100,000 miles to manifest itself, not 300 miles. Mobil Special is designed to compete with non A.P.I. 3rd world budget brand oils, and being SF makes it about 15 or 20 years behind the times. Use the Delvac MX or put some modern name brand oil in your engine.

It sounds like you purchased a car that was treated as being disposable. Too late now, better to take good care of it, but not overdo or over think it, and always keep in mind that once it has been treated as disposable, it is disposable.
 
Thanks for your reply.

I havn’t put it back together yet but I will torque to spec when I do. I’m not sure it had threadlock (manual doesn’t mention it) but I’m glad you agree that it’d be a worthwhile precaution.

I think its fair to say that the issue (or non-issue, depending on your take on it) of zinc in old engines is controversial. I certainly don't know where the truth lies, but I don't discount it as a possibility.

I havn't been able to get a figure for zinc in Mobil Delvac MX, though I posted a query on the Mobil website. Since its a recent spec oil, I'd expect it to be relatively low. Re Mobil Special, in general terms I'd expect it to be lower performance, but in this context being 20 years behind the times may not be all bad. My engine is 26 years behind the times.

I agree there may not be an actual issue with the engine. It seems to be putting a lot of metal in its oil on fairly short timescales, but I don’t have any quantification of that, or anything to compare it to.

The car was used/abused by a surfer dude, so had bad body corrosion and may not have been maintained very well. The people I bought it from rather surprisingly seem to have dealer maintained it by the book, but did nothing about the corrosion, which I think I caught in the nick of time.

It’s a disposable car, sure, but so are most cars (and all drivers). I prefer manual transmission non-cat cars which are hard to find here, so I’d like to keep it going as long as possible. I agree this might have better been achieved by leaving it the **** alone, but I’m in now.

If you can’t fiddle with a disposable car, what can you fiddle with?
 
Ducked:

I looked up Delvac MX (silly me, I previously thought MX meant it was a special oil for Mexico and I always ignored it even though it has always been in my sales catalog). It is a high SAPS high speed marine & trucking oil, not friendly to after treatment systems. It has a starting TBN of 12 while Delvac 1300 Super has a TBN of 10.5. It probably has higher zinc levels than just about any other product in Mobil's line. However, it doesn't carry the mixed fleet diesel/gasoline rating like 1300 Super, it seems it is intended for diesel applications only. Delvac MX is probably one of the oils that the poster from Bolivia, Widman, is recommending for flat tappet engines.

Sorry to get on your case about taking it apart, I love to take apart and put together my machines just because, too.

I always enjoy reading posts by other expats on BITOG, especially in regards to automotive topics in far away countries. I'm going to assume you are American or Canadian by your writing style?
 
Thanks for the reply and for taking the trouble to look up the Delvac. Encouraging as far as it goes, but I note you say "It probably has higher zinc levels than just about any other product in Mobil's line." That seems to imply that your source document doesn't give the zinc content, which seems to be irritatingly common. I'd like to be convinced to continue using the stuff, since its not very expensive on retail here (I bought it at a Carrefour supermarket), but I'd like to see a number.

Re diesel only, I don't have the empty container handy, but I'm pretty sure it had an S rating (SJ I think). Carrefour would be unlikely to carry a diesel-only oil deliberately, though they might screw-up.

It dawns on me that I've been taking the AP classification as a guide to the zinc content, but since, as I understand it, that specifies the upper limit, the actual amounts could be much less, so AP is actually pretty useless as a guide to zinc content. I don’t know where could one find that information.

Re “I'm going to assume you are American or Canadian by your writing style?" Oh Dear! I (guess) suppose it must have rubbed off. I’m from Scotland
 
Been thinking about the implications of the sludge-filled casting void in the mounting face of the oil pump. Since oil can evidently get in to such spaces, I have to assume that sludge could also be washed out, especially with the (presumed) highly dispersant oil I've started using.

This implies that an increase in circulating metal/dirt in the oil after an oil change can't necessarily be related to ongoing wear/oil deterioration/blowby, even if you quantified it. In fact it seems to make it nigh on inpossible to work out what is going on.

I'd guess this void was about 10-20ml (havn't measured it). I could perhaps fill it to stop it sludging up again (say with crumpled aluminium foil?) but it probably isn't the only one in the engine.

I wonder how widespread/significant this effect is?

Might be worth a separate thread?
 
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