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MG Midget and Sprite Technical - Stuck Piston Rings NMC

NMC because it's a Sabre Diesel in a boat.

I've finished de-crudding and rebuilding the head but I suspect some of the compression rings are sticking in their grooves. Not confirmed yet - I won't get to see the engine till Thursday to poke a feeler gauge down the bore.

To get the pistons out means removing the engine from the boat and that's a nightmare I'd really don't want to get into. Cutting decks, hiring a crane at £100 an hour........Jeez - just NO.

So my question is......

Who here in this shedful of oldtimers and curmudgeons knows any really good tricks for freeing sticking rings? I'm nearly sure I'm going to have to do it.

:-(

Cheers in advance.
Greybeard

Not a real expert but how about soaking them with penatrating oil or some kind of degreaser or some such.
Martin Washington

The old way used to be to turn the engine so the pistons were at "half mast" and then topping each cylinder up with a 50/50 mix of diesel and paraffin (kerosene for those over the water) And leave for a day or two.

The problem with this would seem to me to be that this is a diesel, so is presumably well soaked in diesel anyway!

Why do you think the rings are stuck in their grooves?
Guy W

Thx Martin. A few people have said smth similar. One idea was Redex - don't know if you get that your side of the pond.

Somebody said pour some fuel on top of the piston and set it alight to get some heat into it but the idea of burning fuel running down into the crankcase rang some alarm bells.

Somebody else suggested turning each piston just below TDC and using a chunk of wood and a hammer to give a good shock.

I just don't know, but I can see a world of pain coming if I can't find a way.
Greybeard

Thx Guy.

What you said seems to be a consensus so far. The head had been off for nearly a year before I got to it and had just been reinstalled. But the bloody thing wouldn't fire.

That where I came in. I did a compression test and found 1 and 2 good. 3 and 4 very low and 5 and 6 pretty so-so.

Then the owner told me what he had done trying to clean the head and block-deck and torqueing the head bolts. He basically scrubbed it with a handful of steel wool and left it at that. Two of the bolts are specials and he didn't have the tool (I've since made one) and they were between 3 and 4 cylinders. They didn't get torqued down properly.

All the exhaust valves were very badly pitted - to the extent I've just lapped in a set of brand-new valves - but I haven't found anything yet in the head to explain the complete compression loss in 3 and 4. So I suspect the rings as I don't think there was any effective measures to prevent them sticking when the engine was opened up. Personally I would have thrown loads of oil into the bores as soon as the head was removed, but the owner is not mechanically sympathetic.

Thanks again for your help.
Greybeard

Well if the head was off for over a year and the thing left open to (presumably) a salt-laden atmosphere, then stuck rings does sound highly likely! ;-)
Guy W

Yep - that's my fear. Although in fairness not completely exposed. It has been covered up with an oil-soaked towel and the engine-space cover keeps the weather off it.

I hope that if I can free the top rings and get enough compression to get the engine to fire and run the heat might free the rest.

I've done one of these engines before. It's basically the same as the engine in the Ford Cargo three-tonner but it's just such a horror show to get it out of the boat. I'll know more when I can get to the boat.

Thanks gents.
Greybeard

Rod,

I think the answer might depend on whether the rings are stuck with rust or with carbon.

I haven't tried it, but you probably recall all the praise that a 50/50 blend of auto trans fluid and acetone has received. I would certainly give that a try. I have also heard people swear by Marvel Mystery Oil for freeing up engines.

But, if it is carbon, then a different solvent is likely needed. I have a vague memory that some carb cleaners dissolve carbon. I remember some product with a slogan on the label that was something like, "The World's Strongest Carbon Digesting ...", but I can't remember what it was. Anybody? I think it might have been the old formula of Gunk carb cleaner, and I think it may have been a chlorinated solvent.

I would think some heat might help, though I once built fires in the bores of an stuck Farmall tractor engine, and failed to free it after burning for several hours.

Then, before the nightmare of pulling the engine, there are lots of products that advertise to free sticking rings on running engines. Some are fuel additives and perhaps some are introduced into the air stream. So, I would put it together and try that before I would pull the engine.

Good luck with it,
Charley
C R Huff

Regarding Charley's comment on ATF and acetone he may be referring to a recipe like Ed's red for cleaning gun barrels, not that we do that in the UK. See http://handloads.com/articles/default.asp?id=9 or search for Ed's red recipe. Apparently it is good for cleaning carbon fouling in guns and is made from fairly available ingredients so it can't do much harm to try and doesn't seem to have anything in it that would be detrimental to bore or pistons, might be worth an oil flush after use just to be sure the oil isn't effected.
David Billington

Id try the ATF trans fluid / Acetone mix.. ive never tried it, but ive heard its really good

can you pull the sump pan off.... that way you can coat the cly and pistons from below also with anti rust fluid

prop
Prop and the Blackhole Midget

Brake fluid is good for freeing rusted bits. I suggest using a small quantity and leaving it for an hour or so before giving it the push.
Glenn Mallory

Tried Plusgas penetrating oil?

Mike
M Wood

Ive tried all this before with a stuck ring, eventually I had to remove the piston from the engine, drop it into a pan of oil and gently heat that on a camping stove before it would think about moving!

Heat seemed to be the big key. As such, dare i say, you run the engine as is, get some heat cycles through it... or do you see it scoring the bores somehow?
C Mason

Wow Guys, Thanks to all.

Plenty to try in that lot and some great sounding ideas.

Prop, unfortunately there is no clearance under the engine to get the sump off. The engine's right down as low as it can go in the boat's bottom, wedged between two frame stringers.

C Mason - I don't think it would score the bores unless there is a broken ring I don't know about. There's no scoring there at present. The problem is going to be getting enough compression to get the thing to fire at all I reckon.
Greybeard

As a penetrating oil, Plusgas is 10 times better than WD40. I would only use WD40 if I had nothing else and the shops were shut.
Bernie Higginson

I don't know where the original is but apparently a magazine tested various penetrants and tested their effectiveness see http://bbs.homeshopmachinist.net/archive/index.php/t-47279.html WD40 didn't do well and ATF/acetone worked the best.
David Billington

Greybeard
IF the head is off, which I guess it is if you are poking feeler gauges down the bore
The best carbon eater on the planet is diesel EGR valve cleaner sold by Wynns here in a pressure pack but I'm not sure if you have Wynns there---If not,someone else probably has it. Subaru have an upper engine treatment in a p/pack that they use during servicing Either of these will free up them rings for you--just give em a good soak overnight
Don't breath either of them though, they've got stuff in there that isn't at all nice, believe me.
and make sure you clean it out after cos as I'm sure you know , them there diesels will run on whatever you feed em and they really bolt on this stuff
cheers
willy
William Revit

That's an interesting one Willy. Thank you.
I think the local tractor repair guys might have smth like that.

Cheers.
Greybeard

Also Bernie and David - cheers.

I think I know where there is some PlusGas.

This place is in the 19th century. It's hard to get quality stuff here, everyone wants cheap crap. Still - there's always Amazon.
Greybeard

Greybeard

Any of the agricultural machinery, boat repairers or chandlers near you have any suitable penetrating fluid for sale?

Plusgas available from:
http://uk.rs-online.com/web/c/facilities-cleaning-maintenance/greases-oils-lubricants/lubricants//?redirect-relevancy-data=636F3D3126696E3D4931384E5461786F6E6F6D794272616E64266C753D656E266D6D3D6D61746368616C6C26706D3D5E5B5C707B4C7D2D2F5D2B2426706F3D313626736E3D592673723D52656469726563742673743D4B4559574F52445F53494E474C455F414C5048415F4E554D455249432677633D4E4F4E45267573743D506C757367617326&r=f#applied-dimensions=4294966409&sra=oss


Hopefully you can find a more local supplier - my old motor factors and Unipart used to stock Plusgas. I got my local tool and hardware shop, Caldwell Wrights, to order some in for me.

If you want acetone you can get this from grp suppliers (e.g Allscot in Glasgow).

I have found Plusgas got seized MkI/II Sprite combined brake and clutch cylinder pistons out after a long soak.

Cheers
Mike
M Wood

Plusgas available like on Amazon too. Spray can, or 500ml or 1 litre cans - sou nods like you'll want the 500ml or 1litre cans
M Wood

I found two cans of PlusGas and Yes - the tractor repair place 5 minutes walk away has EGR valve cleaner and other stuff in stock.
Now if the dam' rain would stop....
Greybeard

You can send some rain here if you want
It's full on bushfire season here and as dry as
Our electricity here is hydro generated and the dams are down to about 20% capacity, the lowest they've been for years-- There's a power cable from mainland Australia but it's got itself broken somehow about 100klms out to sea and won't be up and running for a couple of months
Our island state here is roughly 300klm x 300 and on the news tonight they said there is roughly 80 fires going and about 50 of those are out of control at the moment
Some of your rain would be real nice if you can spare some
Cheers
willy
William Revit

Crikey Willie.

Help yourself. As much as you like.

Stay safe mate.
Greybeard

This thread was discussed between 19/01/2016 and 22/01/2016

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