My old 2A Diesel Landie is well underpowered and chucks oil out of the oil filler pipe. Previous posts here basically suggest crankcase pressure - rings blowing.
Before I fork out for a re-bore & new pistons - I intend to try a re-hone and new rings. I bought the gadget - basically three long flat stones that are sprung against the cylinder walls. Supposedly they will de-glaze and hone the cylinders, the suggested lubricant being brake fluid.
So - has anyone done this - any suggestions?
The job on the face of it seems straightforward..:
drain oil & remove sump
remove head after disconnecting air filter, plugs and injectors
check what size pistons / rings are in, order new ones
Undo big end bolts, remove caps (keeping good record of order etc.
pull out pistons and conrods.
Hone cylinders, clean up well, smear with oil.
Wait weeks for new rings to arrive :-(
Fit new rings (clean grooves first)
Using ring compressor, re-fit pistons, tighten up big ends, replace cylinder head, injectors, sump etc.
Fill with oil.
Turn key, starts first turn, drive carefully to avoid low-flying pigs.
1: Exhaust and intake manifolds. Have fun with the exhaust manifold bolts.
2: The head is heavy.
3: While you have the head off, check the valves. The valve-stem seals are probably worth replacing.
4: You don't absolutely need to remove the injectors from the head, but as I recall, the nozzles stick out just enough to be vulnerable. And it's easier to turn the engine to check valve clearances with them out.
Not missed a lot and with the other advice should be OK
I did the same with an Armstrong Siddeley .... the hone needs to run at a slow speed .... not the full speed of the drill more like a couple of hundread revs to get the best results ..... I also used a 90 grit flap wheel after honing to get the fine cross hatched finish ... well finish- ish ...as the hone left some deep scores .... but thats maybe my lack of technique ... i used parafin as a lube .... oh and mind the ridge at the bore top if you can remove it with a scraper (from an eng tool suppliers) first it makes the honing easier .... if you dont get rid of it the worst is that the new top ring will hit it and break. the best is that you get an anoying tapping noise as the top ring hits it at every TDC of the piston .... they used to make stepped rings to leave space for the ridge at one time but probably not anymore for a series 2 engine but might be worth asking ... try Brown Brothers or Sutton Rebore Services (Sutton Surrey UK) for rings .... both on the web
On or around Thu, 15 Apr 2004 09:54:06 +0100, "Floatything" enlightened us thusly:
get hernia repaired, buy truss for replacing head later.
having made special tool, spend about a day cleaning ring grooves. Don't be tempted to use a bit of old piston ring. I made a cunning tool from a gash small screwdriver The end is something like this shape:
| | \ ( \_\
and has a tapered cross-section, the right side above is thicker than the left. The bottom pointy bit is sharp. You use it to scrape in left-right direction as shown. The thickest cross-section is slightly under ring groove width.
I'd fit new big-end bearings while you're in there. If you doubt the main bearing condition, you may be able to change them too - the difficult bit there is getting the top shells out.
find that the battery is naff, charge same.
or have another battery and some jump leads handy. sometimes a rebuilt engine is stiff to turn.
METHOD I USE ...... Drop conrods off the crank .....gotta do that to get em out so good !! slacken fan belt ....sounds daft but will become obvious later slacken all the main cap bolts 1/2 turn a bit at a time Remove one cap at a time and change bottom shell then using a thin screwdriver crefully tap the top shell round towards the side with the nib. Now the crank is slack it will drop away from the block housing at all main positions enabling you to ferret the sheel round and remove it Install new top shell by sliding it back in from nib sdie Seat shell and nib in block fit cap hand tight and do next one. The fan belt needs to be slack to allow the crank to drop slightly to create the clearance !!!!!!! thats the trick
Watch out for the cork seals in the back cap ....recover them carefully and refit to the CAP not the block or pref renew them. when you done all of them tighten the caps slowly and torque up ..... it does work with a landy engine as the back and front caps are not side bolted to the engine as they are on say a BMC Bseries engine.
I spoke to a 4X4 specialist yesterday who said that in his experience the improvement gained from a re-hone is short-lived ("a couple of months") and that in the long term I'd be better off having a re-bore.
On or around Sat, 17 Apr 2004 10:05:25 +0100, "Floatything" enlightened us thusly:
depends on the condition of the bores and how worn they are, also how worn the pistons and rings are.
The seal of the pistons in the bores is mostly about ring gap, and somewhat about ring clearance in the groove. When new, the ring, when at operating temperature, is designed to almost-fill the gap between the piston and the cylinder. it has to have a gap, so as it can expand when it gets hot without jamming in the bore. As the ring wears, it gets narrower (the outer circumference wears down) and so the ring gap (between the ends of the ring) gets bigger. Also, the gap between the inner surface of the ring and the bottom of the piston groove gets bigger. Bore wear also causes these effects.
-------------------------------------- | | piston | |_______ ||¯¯¯¯¯¯| | cyl ||______| | Worn ring and worn bore | | plus damaged ring groove | ____'¯¯ | | step in groove
--------------------------------------
somewhat exaggerated, but that's what I'm getting at, and ascii-art has its limitations :-) As well as wearing at the outer edge, the ring also wears on both faces (top and bottom) and so becomes a looser fit in the groove. The ring when new has a small clearance int he groove, for expansion again - if the ring becomes stuck in the groove it stops working.
All the wear on the ring contributes to poor sealing and loos of compression and blow-by on the power stroke. by replacing just the rings, you haven't cured any wear in the bores, nor have you cured any wear in the piston grooves, though IME these don't normally wear much. You need to hone the bores, so that the new rings will bed in properly. Ovality of bores is also a problem.
As to whether it's worth it, well, you have to take it on a case-by-case basis, really, and you'll not know until you lift the head and examine the pistons and bores. If there's a step at the top of the bores that's more than a few thou'[1] tall, then the bores are significantly worn and there's probably not much point in just replacing rings. You can also measure (if you have the kit or can borrow it) the bore below the step. I'd say, off the top of me head, that a step of more'n about 5 thou, i.e. 10 thou on the bore, would be a waste of time as regards replacing rings. Normal rebore sizes are 20 thou and 40 thou oversize, for reference.
If the step is small-to-non-existent, then you have a good chance of getting reasonable results from a ring change. However, you do also have to consider the pistons themselves - these need careful examination, both for excessive skirt wear (which makes 'em loose in the bore) and for any cracks or burning, or damage to the ring grooves.
bearing in mind the price of pistons, it's doubtful whether it's worth replacing pistons *and* rings without doing a rebore as well - if you're getting new pistons, you may as well do the whole job and make it as good as you can.
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