Engine flushing?

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Engine flushing?

Postby Ducked » 13 May 2012, 15:08

While re doing the valve clearances ("hot", like you're supposed to) yesterday, I carelessly "parked" the two rocker-cover bolts in the wrong (air cleaner hold-down) bolt holes, which were dirty.

Didn't realise what I'd done until after a freeway run into Tainan and back (maybe 40-ish k). Nasty streak of "silt" from the bolt holes, inside the rocker cover.

Damage limitation would suggest taking it for another run to stir up the oil (though this'll probably cause more wear) then doing an oil and filter change, annoying because I did it very recently (Delvac MX 15-40).

Is it likely to be worth doing an engine flush as well? Don't remember seeing flushing oil here, but then I havn't looked.

I've got a lot of hydraulic oil and some 2-stroke, so perhaps I could make my own?
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Re: Engine flushing?

Postby sulavaca » 23 May 2012, 21:46

What vehicle is this?
Am I reading your post correctly? You screwed into and through the rocker cover, releasing dirt into the engine?
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Re: Engine flushing?

Postby Ducked » 23 May 2012, 23:13

sulavaca wrote:What vehicle is this?
Am I reading your post correctly? You screwed into and through the rocker cover, releasing dirt into the engine?


Well almost that bad.

I got dirt on and in the rocker cover bolt threads, was interrupted, then, short of time, put it back together in a hurry without remembering to clean up the threads, releasing dirt into the engine.

Of course some damage will already have been done, and there'll be some abrasive that won't be removed by anything short of a full strip-down (embedded in the soft metal bearing shells, for example) so the best I can expect is to limit rather than eliminate it.
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Re: Engine flushing?

Postby sulavaca » 24 May 2012, 12:47

I can't picture how bolts screwed down into the rocker cover, somehow protruded to the inner side of it. :eh:
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Re: Engine flushing?

Postby Ducked » 24 May 2012, 17:42

Uh? How could a rocker-cover hold-down bolt do its thing if it didn't go through?

Funnily enough I can't actually remember the precise arrangement on all previous cars, getting old, but the Daihatsu arrangement didn't strike me as particularly unusual.

It has 2 long bolts that go through bronze-looking washers backed by gaskets that seal the (unthreaded) entry holes in the cover, and then screw into the head. (Actually into the camshaft pedestal IIRC)

I think the Marina 1800 B series engine had a similar 2-bolt arrangement. The Lada had a lot of small bolts and washers around the perimeter of the rocker cover that were a bit of a pain but would avoid this problem (as would a modicum of care :oops: ) since they were in or outside the rocker cover gasket. Ford Pinto...um, not sure, like the Lada I think, Sierra DOHC likewise. Triumph 1300, 2-bolt, I think. No recollection at all of any of the others, but from that sample it is the less common (BL only) arrangement.

Anyway, there's a gap between the rocker cover and the head, where the bolt threads (and any dirt they contain) are exposed to oil splash, plus the threads get scraped cleanish entering the head and the excess gunge gets deposited on the head surface, where it is also exposed to oil splash. This puts the dirt in the oil.
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Re: Engine flushing?

Postby sulavaca » 24 May 2012, 19:40

I can't build a picture in my head of what you're talking about I'm afraid. I know there are a host of different ways of securing a rocker cover, but I thought you were talking about air pipe/cleaner retaining bolt threads in the rocker cover, not screw threads in the head. I'm totally confused. I need a photo.
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Re: Engine flushing?

Postby Ducked » 28 May 2012, 18:55

sulavaca wrote:I can't build a picture in my head of what you're talking about I'm afraid. I know there are a host of different ways of securing a rocker cover, but I thought you were talking about air pipe/cleaner retaining bolt threads in the rocker cover, not screw threads in the head. I'm totally confused. I need a photo.


Cut-away schematic might be better?

Image
rocker cover hold-down bolts by ed_lithgow, on Flickr

My recollection is that more of the bolt than is shown here (perhaps all of it) is threaded, (giving it more dirt-trapping capacity) but I might be remembering that wrong.
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Re: Engine flushing?

Postby sulavaca » 28 May 2012, 21:02

Ohhhhhh! Now I get it!

That's a very old design indeed. Not too many rocker screws go through the open breather space in the rocker cover any more. The cover tends to flex too much with these designs, which often leads to early leakage around the rocker cover gasket area.

I wouldn't worry too much about it though. They couldn't have been that dirty could they?
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Re: Engine flushing?

Postby Ducked » 28 May 2012, 23:45

sulavaca wrote:Ohhhhhh! Now I get it!

That's a very old design indeed. Not too many rocker screws go through the open breather space in the rocker cover any more. The cover tends to flex too much with these designs, which often leads to early leakage around the rocker cover gasket area.

I wouldn't worry too much about it though. They couldn't have been that dirty could they?


Yeh, well, its a very old car, so it would be. Doesn't seem to flex or leak though.

The rocker cover is cast aluminium and has a central baffle box, all of which probably makes it quite rigid, at least as compared to the pressed-steel two-bolt BL designs I mention having had, above.

I think it was pretty dirty, judging by the streak of muck from the bolt holes. :doh: :doh:

After the last freeway run the oil film on the camshaft lobes seemed to have a greyish appearance, suggestive of very rapid wear, :doh: :doh: :doh: though it could be (at least partly) imagination.

No time at the moment so I won't drive it any more until I can attempt some damage limitation.

I'd like to fit an oil accumulator anyway so if I can get some of the fittings I might be able to use them to flush out the oilways before I start it up again.
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Re: Engine flushing?

Postby Ducked » 27 Jul 2012, 21:17

Since I havn't made any progress with the oil accumulator idea, and will be busy with a sodding summer school next month, I'm thinking I might just do a DIY engine flush to remove as much of the silt as I can.

Heres "THE PLAN" (or at least A plan)

The basic idea is to use 3 changes of 30% 2-stroke as a flush while turning the non-firing engine over with the plugs out, then, after changing the oil filter, do a couple of close-succession changes (say 100 miles or so) with Delvac 15W/40 and (very old) Mobil Special 20W/50, before resuming normal oil change intervals. I'd have to watch the very old Mobil Special for signs of short-term instability.

I'm assuming that, while 30% 2-stroke is probably a relatively poor lubricant, it won't be too damaging in a non-firing engine, and may flush out grit that would be retained by thicker oil. 30% is still a high oil % compared to a typical 2-stroke engine running at, what, 2-5 % ?

Seals are presumably made to withstand some petrol contamination of the oil, (though of course not that much) and they won't be exposed for long or at very high temperature.

Possibly, perhaps after filtration/settling, the 30% petroil mix could be diluted further and burned in a 2 or 4 stroke engine.

Comments? Safe-ish or guaranteed fatal?

A possible alternative would be to use a commercial engine flushing machine service, but I'm not sure what that'd cost, or that it'd necessarily be better.
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