Freeing a seized engine with compressed air

[09112]

I've seen several items on the web that recommend the use of compressed air to free a seized engine. Can anyone tell me if there is a fitting that can be purchased for such a method? And how about the down side, can there be a danger to life or limb? I would be interested in hearing from anyone that has actually used compressed air.

 

[oldnslo]

I believe that you can purchase a fitting that screws into the spark plug port. Problem is that the valves have to be closed for this work.

Danger is suddenly moving parts and potentially no lubrication on any of the bearings.

 

[George2615]

I've seen a few seized engines and doubt that compressed air would free them up. Usually an engine seizes due to water that got inside and rusted the rings to the cylinder walls or lack of oil that causes the bearings to seize to cam, crank, etc.

oldnslo is correct that compression tester hoses can be adapted to attach a compressed air line but vales must be closed and if air does push the piston down the valves will start to open defeating the purpose.

IMO a seized engine needs to be taken apart to see why it seized and what needs to be done to repair.

 

[RedNeckRacin]

only way I have ever heard to break a seized engine is filling the cylinders with atf + acteone or pb blaster or a light oil. Let it set, and try to roll it over with a socket on the crank.

 

[Egon]

There are some engines designed to start with or compressed air. Tying an air hose to a spark plug access only allows one stroke and that only if the cylinder with closed valves has been chosen.

 

[Rock Crawler]

only way I have ever heard to break a seized engine is filling the cylinders with atf + acteone or pb blaster or a light oil. Let it set, and try to roll it over with a socket on the crank.

My father in law is big into auctions and buys "junk" often. Using the method above, he almost always gets a frozen/old engine to turn over and get running. That is old school, but still works today as always.

 

[Stimw]

I have 2-3 of the fittings that are home made that I used to replace valve seals without removing the cylinder head.
You just knock the guts out of a spark plug then weld/braze an air fitting to it.
With the fitting on a cylinder and air on it you CAREFULLY remove valve keeper, spring and replace the bad seals. The air will hold the valve closed.
That is old school and I haven't done it in years!
The stuck engines I have seen were too far gone for air to do anything.

 

[RickB]

If a shop air supply frees a stuck engine, it wasn't badly stuck to begin with.

 

[bigdeano]

I've seen stuck engines moved with hydraulic pressure applied to the spark plug hole, but air pressure is probably too low if the engine is stuck very badly.

 

[PILOON]

While I don't believe air would free a stuck engine I do know that air will pop a cylinder head once the bolts are removed.
Even well seated gaskets don't resist and I prefer air to using a pry bar.

 

[Sawyer Rob]

Sometimes a steam cleaner will "free up" a motor...

You put steam into the intake, exhaust and into the spark plug holes... The hot steam expands the metal enough, to many times, break it free...

SR

 

[Texasmark]

Let's run some numbers as I have nothing to do this morning.....it just rained on my "down" hay so I can't bale it .

Thinking about force applied, like with a torque wrench in ft-lbs. Force = pressure x area. Pressure (considering the valves are closed which as stated above may not be the case.....tough luck) is say 125 psi; best you can get from a single stage compressor.

For area let's take a single cylinder of a Ford and a Johnny Popper....guessing at the diameters but close enough to see where we are. Ford take 3". Popper take 7".

Area of the piston is 22/7....aka 3.14 x (ｽ the diameter x ｽ the diameter).

Ford: 3.14 x (3"/2 x 3"/2) = 3.14 x 2.25 = 7" surface area.

Force applied to piston is 125 psi x 7" area = 883 ft-lbs.......Yepper that's a sizeable force pushing down on that piston. No need to go to the popper but let's do it anyway.

Popper: 3.14 x (7"/2 x 7"/2) = 3.14 x 12.25 = 38.5" surface area.

125 psi x 38.5" area = 4810 ft-lbs. Yepper that really IS a sizeable force.

Add that to a long stroke for good torque and you see why John decided that a 2 jug, syrup bucket engine would be to a farmer's advantage when needing something to do some serious work.

Course what's missing from the above is the added whammy when the injector squirts a mist of diesel in the compressed air generated by the compression stroke.

So, compare that to you on your pipe wrench on the crank shaft trying to rock the engine back and forth after you soaked it good with some sort of release agent.

Yes sir. Compressed air is a tool. Course with a multi cylinder engine luck would have it that you could have at least one cylinder with the valves closed.

 

[TimberHole]

Let's run some numbers as I have nothing to do this morning.....it just rained on my "down" hay so I can't bale it .

Thinking about force applied, like with a torque wrench in ft-lbs. Force = pressure x area. Pressure (considering the valves are closed which as stated above may not be the case.....tough luck) is say 125 psi; best you can get from a single stage compressor.

For area let's take a single cylinder of a Ford and a Johnny Popper....guessing at the diameters but close enough to see where we are. Ford take 3". Popper take 7".

Area of the piston is 22/7....aka 3.14 x (ｽ the diameter x ｽ the diameter).

Ford: 3.14 x (3"/2 x 3"/2) = 3.14 x 2.25 = 7" surface area.

Force applied to piston is 125 psi x 7" area = 883 ft-lbs.......Yepper that's a sizeable force pushing down on that piston. No need to go to the popper but let's do it anyway.

Popper: 3.14 x (7"/2 x 7"/2) = 3.14 x 12.25 = 38.5" surface area.

125 psi x 38.5" area = 4810 ft-lbs. Yepper that really IS a sizeable force.

Add that to a long stroke for good torque and you see why John decided that a 2 jug, syrup bucket engine would be to a farmer's advantage when needing something to do some serious work.

Course what's missing from the above is the added whammy when the injector squirts a mist of diesel in the compressed air generated by the compression stroke.

So, compare that to you on your pipe wrench on the crank shaft trying to rock the engine back and forth after you soaked it good with some sort of release agent.

Yes sir. Compressed air is a tool. Course with a multi cylinder engine luck would have it that you could have at least one cylinder with the valves closed.

Your calcs don't tell the whole story. The torque applied to the crank is not only function of the pressure but also the arm. When the piston is at TDC the arm is zero and all the pressure in the world will put zero torque on the crank. When doing compression tests on aircraft engines we put the piston at TDC, stand clear of the prop and add 80 psi to the cylinder. I do agree air is a tool but it doesn't seem like an overly effective tool in this case. I do like the idea of popping the head with air pressure.

 

[GLyford]

only way I have ever heard to break a seized engine is filling the cylinders with atf + acteone or pb blaster or a light oil. Let it set, and try to roll it over with a socket on the crank.

The other I have heard of is a whittled down piece of wood, and careful taps with a sledge...

 

[RedNeckRacin]

My father in law is big into auctions and buys "junk" often. Using the method above, he almost always gets a frozen/old engine to turn over and get running. That is old school, but still works today as always.

I learned it from an old school guy as well. I never had to use it, but figured its one of those little tid bits of knowledge thats worth carrying along and passing around when needed.

The other I have heard of is a whittled down piece of wood, and careful taps with a sledge...

Haven't heard of that one but I think it would work well to break that initial hold.

 

[fidowanttobe]

My father in law is big into auctions and buys "junk" often. Using the method above, he almost always gets a frozen/old engine to turn over and get running. That is old school, but still works today as always.

Sounds like a friend of mine. I've seen times he had to pull the head and pan, then jack up the front of the tractor with the jack resting on a rod journal! ATF and acetone and whatever other concoction in the cylinders, a 3' or 4" diameter piece of aluminum setting on the piston with a 5 pound sledge resting beside it. Whenever he walks in, he gives it a whack. I know he has saved WAY more tractors than he has parted out so, . . . must be doing something right.

 

[CincyFlyer]

... Course with a multi cylinder engine luck would have it that you could have at least one cylinder with the valves closed.

Yank the rockers and pushrods and you can have all of the valves closed. Then you can try the pistons that are about halfway through the stroke.

 

[09112]

Thanks for the suggestions guys. I will just have to take my time on this one. The first one I tried I ruined the block. This one I'll save if possible.

 

[Sawyer Rob]

The other I have heard of is a whittled down piece of wood, and careful taps with a sledge...

I've done that...

I turned down a piece of oak to "bore" diameter with a lathe and then got after it, continuing to soak the engine... Every day I give them a few hits in each hole, until they come loose...

SR

 

[ultrarunner]

Soaking and rocking...

If the car can be rolled then rock it.

If a bare engine the big breaker bar with socket.