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Old 28-04-09, 08:35 PM   #21
rustyreks
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Default unseizing pistons

I normally find it is a combination of different methods will free an engine an engine that is really seized will need some type of pressure whether thats a hammer and a block or filling the head with grease and pressurising it to move the piston i have tried adding some phosphoric acid in with some auto transmission oil and that broke the rust barrier and allowed the oil to penetrate i also have tried the heated oil which works well i used the auto transmission oil again for that as it has a high boiling point i used that to unseize brake cylinders off morrie minor these can be awkward as they are single sided but heating them in oil worked well once heated you gently tap them from the opposite side of the cylinder and they just pop out.
The toughest engine i did was a lister diesel single cylinder the diesels are much tighter than petrol engines I used
the phosphoric and oil trick plus the hammer and block the vibration plus turning with a large cresent it took about 3 weeks trying to turn it every day to free it up as it turned out it had seized at the bottom of the cylinder and only had some minor pitting to the bore so was able to be salvaged it was quite a challenge not my motor a friend of mine who asked for some help on it.rustyreks
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Old 28-05-09, 08:24 PM   #22
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I heard a good un recently...

Get yourself an old spark plug and an airline nipple. Remove the ceramic bit of the plug, until you have the metal end with a hole through it. Weld the air line fitting to this.
Squirt a load of your favoured freeing agent down the plug hole, and fit your new plug. Attach airline to compressor, and gently pump up the cylinder. The extra pressure forces the freeing agent past the rings better than gravity ever could. Obviously you need to make sure the valves are shut...
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Old 28-05-09, 08:50 PM   #23
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Sorry Greenbat, this is very dangerous...

Add you favourite penetrating agent, say diesel (quite effective). Add air then compress to, say, 260 psi.

Does this sound familiar? Of course it does, its exactly the circumstances inside a diesel engine at ignition. If you don't blow your face off, you will probably bugger the engine.

NEVER mix compressed air with any kind of fluid.

If you fill the cylinder with a fluid (heavy oil or grease is good) then rig up a pump to force more of the same into the cylinder; sometimes it works.

Martin.
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Old 28-05-09, 08:59 PM   #24
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Quote:
Originally Posted by martinpaff View Post
Sorry Greenbat, this is very dangerous...

Add you favourite penetrating agent, say diesel (quite effective). Add air then compress to, say, 260 psi.

Does this sound familiar? Of course it does, its exactly the circumstances inside a diesel engine at ignition. If you don't blow your face off, you will probably bugger the engine.

NEVER mix compressed air with any kind of fluid.

If you fill the cylinder with a fluid (heavy oil or grease is good) then rig up a pump to force more of the same into the cylinder; sometimes it works.

Martin.
Yes, if you went that high. The pressure I heard was around 110, though that is probably a bit high too. The idea is just to force the oil past the rings, so it penetrates and frees up as previously described, not use the whole might of the compressor to blow the lump to bits. Perhaps a footpump up to about 30-50psi might be more suitable, and available?
But yes, good point. Do try not to blow yourself up.
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Old 28-05-09, 09:20 PM   #25
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I realised that you probably intended a lower pressure, BUT, (since you're doing an engineering apprenticeship) this should stand you in good stead... NEVER mix compressed air with any fluid. 99 times out of 100 you'll get away with it - the other time your employer will not thank you for making him liable for the accident you just caused. There are better and safer ways of doing this.

Martin.

Oh, P.S. In case you wondered, I am an aircraft engineer with 30 years experience. We deal routinely with many different compressed gasses and fluids; trust me, they don't mix!

Last edited by martinpaff; 28-05-09 at 09:23 PM. Reason: P.S. added
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Old 04-07-09, 08:02 PM   #26
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Use the cheapest "cola" that you can find .This will have the largest ratio of Phosphoric acid to flavourings and sugars, neither of which you want. Look at the prices of cola, WD40, diesel and releasing oils, you will find cola the cheapest by far. A friend had a piston which had been left outside for more than 40 years, it freed off in 6 months, during which time he restored the rest of the engine.
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Old 07-09-09, 09:36 AM   #27
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Quote:
Originally Posted by martinpaff View Post
I realised that you probably intended a lower pressure, BUT, (since you're doing an engineering apprenticeship) this should stand you in good stead... NEVER mix compressed air with any fluid. 99 times out of 100 you'll get away with it - the other time your employer will not thank you for making him liable for the accident you just caused. There are better and safer ways of doing this.

Martin.

Oh, P.S. In case you wondered, I am an aircraft engineer with 30 years experience. We deal routinely with many different compressed gasses and fluids; trust me, they don't mix!
quite right martin, v.v.v.v.v.v.v. VERY dangerous. even inert gasses wouldnt be considered as foolproof, its just not worth the risk, and what you must remember is, if an engine can make an effective seal at normal compresion levels (someone else can quote these pressures) then combined with rust it will be quite capable of resisting compressed WD40 (for example) going in at pressure, you may as well just let it soak or give it a well calculated bat with a hammer.

i like martin, am an engineer, though not anywhere near as experienced as martin, but i helped my dad with an investigation at electrolux into an explosion on one of their presses, it turned out that the normal gas (nitrogen) had been substitued for oxygen for use on the dicharge blast, the combination of oxygen and a leak of hydraulic fluid left a guy on life support for quite some time.

be very careful

Paul.
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Old 11-12-09, 09:49 PM   #28
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Wink freeing stuck pistons

I have unfrozen pistons with the help of fire.,
with the cylinder head removed i poured a mix of oil / diesel/ petrol into cylinder and placed a bit of lit rag is also , it should burn for about 1/2 hour alowing expansion to occur breaking the rust ring and allowing oil to run down past stuck piston.
I have used this method a few times both on stationary engines and tractors.
works well.
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Old 11-12-09, 10:10 PM   #29
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That sounds a good technique, just don't do it with an alloy block!
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Old 12-12-09, 12:53 AM   #30
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i freed off an international td 18 crawler engine a few years back by filling the bores with diesel and leaving them for a week then getting a block of wood as close to the bore size as possible and giving each piston a reasonable clout in turn till she relented just take your time and be patient and they will usualy give in . got a lister d that will be another exhibit in time and she is solid so has been soaking for at least 15 months all we do is pop the plug out occasionally and top up with sas penetrating oil if needed of all of the penetrating oils i have tried over the years this one seems to work and is half the price of scented wd40 but thats only my opinion some swear by wd 40 but we use a lot of this at work purely on the it works basis and have switched from wurth to this as wurth is very expensive for what it is
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