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Gummed up or seized


Fuzzy-Felt Bloke
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Good morning

 

I came by a small diesel engine (DC Merlin) which appears to me gummed up. I've soaked in Glow fuel for two day without any luck and placed in an oven (220) for 15 mins, again without any luck. I assume the engine is seized. What are your thoughts and is there anything more that I could try?

 

Thank you for reading this

 

Kind regards

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Welcome to the forum fuzzy.
 

I would try stripping the engine carefully - start by removing the backplate. Try to establish if it’s the crankshaft, piston or both which are stopping rotation - very carefully starting to unscrew the cylinder barrel would reveal if the piston has seized but beware of damaging the con rod. If seized, carefully tapping the piston crown with a brass drift as close to bore size as possible might free it.  
 

I would heat the engine again before trying to free any parts but it might be worth soaking in kerosene (paraffin) rather than glow fuel before you start. 

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i would try soaking it in some model diesel fuel if you have any. The Ether should really help soften it all up. 

 

If that fails then Martin's suggestion is the next logical step. If you can avoid stripping it completely that is good as the piston/liner have run in their current position for years and are well mated to each other. Moving them may result in a loss of performance. Whipping off the backplate is a good idea though to help get some juice inside the engine 

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I'm gonna have the same job on my hands next week when I pick up 2 Diesel Powered gliders from a fellow club member which both diesel engines haven't run for around 20 - 25 years... But I know a man that loves playing with engines and he will get them running almost like new again.. Both engines are 1 & 1/2cc PAW's

 

 

WhatsApp Image 2023-09-25 at 20.22.49.jpg

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With the through screws removed it should pull off but you may need to give it a twist given how gummed up everything is and you might even need to make a small tool with two pegs that will give the leverage required. Its a faff having to make it, but better than shredding the backplate with mole grips. 

 

Before all that and as a starter for 10, sling the thing in a pot of model diesel fuel and leave it for a week. Dont muck about, just drown it in a jam jar for at least a week. 

 

Once you fish it out fit a prop and see if you can get it to budge at all. I would do this cold on the basis that it will still be wet with the fuel and once the castor seal is broken fuel will flow into these 'dry' areas and help free them up. Once you get it to move 99% of the job is done. 

 

I had to go through this little adventure with my Dads AM10 a little while ago and it did take a while to get things moving. 

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DC merlin, nice little engine...

 

Find jam jar so whole engine minus prop can be submerged in ordinary car petrol and allow to soak for 2 days or so.

 

You realise the FIRE risk ?

 

With lid on the jar can be shaken, see castor "gum' floating about and resting on jar bottom.

 

The back plate is held on by the two thru crank case bolts/nuts.

 

With those bolts out you can turn the back plate to free it but gasket will be mangled.

 

With back plate off you can use screw the cylinder head and remove the cylinder leaving the piston and rod in place 

 

The prop driver plate is a taper fit on crank. No "oil way" in crank case nose to clean.

 

If a soak in petrol fails, try old small sauce pan ( or a new cheapo small sauce pan ) and car engine old. Submerge engine in oil and heat gently on a camping stove  OUTSIDE on a gaurantee dry day. Once you see the nearest hint of the oil smoking, turn off the heat !

 

Hot oil is a very great FIRE and SKIN BURN risk, a very great risk !!!  So no pets, kids ( or dumbasses ) anywhere near the hot oil !!!!!!!!!!!!!!

 

 

Spectre.com iirc will have a report etc. on this little gem of an engine.

 

Take note about rod/piston/cylinder alignment.....

 

Try soaking in petrol to see if  it will "free off and turn" but be gentle...

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I know someone who makes 80 percent alcohol which works really well but is dangerous stuff and gives me a splitting headache.

 

Shifts burnt on carbon and everything but absorb moisture like mad and evaporates quickly.....as said, dangerous stuff...

 

My d1000 is how much a litre these days ?

 

Modern petrol had "additives" these days...easily available and is a fire risk, but what of glow and model diesel fuels ?

 

This hobby is full of risk as we know......so act accordingly.

 

Take care out there...

 

 

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Fit a prop, "borrow" the wife's hair dryer, apply gentle heat and GENTLY  rock the prop back and forth gradually increasing the arc of movement back and forth over time. As the castor heats up the motor should free up. When you can turn the prop through 360 add after run oil and turn the prop to distribute in the engine. Works for me every time, a word of caution, ware gardening gloves as the motor will get hot. 

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Think good quality " geometry/engineering drawing set"  and thickish brown envelope for the new gaskets...

 

No real need to remove the prop driver plate ( taper fit ) as no crank case " oil way"......

 

Enjoy this little gem of an engine.

 

Ps is your back plate central spigot hole threaded by chance ?

 

 😀

Edited by Rich Griff
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If you intend cleaning the crank then the prop driver plate will need to come off.

 

Remove the finned cylinder head then the cylinder ( if it free of the piston that is ) then the piston/rod off the big end journal noting which way round the rod is.....

 

Then the prop driver plate can be removed. It's alloy so will expand more quickly than the crank.

 

 

Threaded spigot, for alternative tank, or use the "squarish " plastic tank. Alternatively a "remote tin tank ".

 

You have some dc advertising of the era ?

Edited by Rich Griff
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With the conrod in the position it is i would favour turning the engine backwards (clockwise viewed from the front, anti clock viewed from the rear) as this will put the conrod under tension and not compression meaning you are far less likely to bend it. There may also be accumulated debris on top of the piston which will be incompressible so once its at bottom dead centre and moving freely make sure you can see through the exhaust ports across the engine. If you have an air line handy a quick blast through the exhaust port wouldnt hurt. 

 

When it comes to turning the engine right over make sure the combustion chamber is not full of fuel to prevent hydraulic lock. Turn the engine over slowly and gently. If it seems like its hitting something solid stop and find out what it is. 

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5 hours ago, Fuzzy-Felt Bloke said:

Hi Rich

 

Yes, the spigot is threaded. What is this for?

 

Later versions of the Merlin had plastic then metal tanks retained by a single central screw.

 

PICT1342.thumb.JPG.551b066bebeef92f3cb50f5ff18e055b.JPG

 

Early Merlins had smaller plastic tanks retained by the same backplate screws.

 

PICT1344.thumb.JPG.15738439f430ddf760b9870d90c3fd76.JPG

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