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.