How much liquid is needed to hydrolock an engine?

[zorobabel]

Lets say you do a piston soak on a 2L 4 cylinder engine.
After the soak is done (assuming liquid is still pooling on top the pistons), the engine is slanted so the liquid pools to one side and the liquid is vacuumed out using 1/4" tubing. Little liquid is left pooling on the slated piston tops. Do you think this is enough to hydrolock the engine?
I've seen it mentioned to crank the engine after the soak with plugs, coils and injectors removed/disconnected; I've done that once and I got some mist out, but I wonder if it is really necessary.

 

[WyrTwister]

Do not know if it is necessary , but that is pretty much what I would do .

 

[mrsilv04]

I'd crank it with the plugs out, just for the peace of mind. Then you know.

 

[ARCOgraphite]

Depends on CC size, ring tension, valve overlap.

I wouldn't worry with a slow starting crank. More an issue of ingesting junk like "seafoam" at 2500 rpm too quickly.

If you are doing a soak you SHOULD pull the plugs. You don't want to force crusty junk down past the ringlands or trash your plugs.

 

[RLS]

When the the volume of the liquid exceeds the volume of the combustion chamber at top dead center you may have hydro lock. Now since pure liquid cannot be compressed other weaker parts may give way. A head gasket may push out, a rod may bend, the crankshaft may bend, a main bearing may compress. I have seen the crankshaft pushed out the bottom of the engine, splitting the block in the progress. It all depends on the amount of torque applied. If you are turning it over by hand and you feel it lock, rotate it backward and the fluid should be expelled out the exhaust. I have had my mechanics bend rods on Cummins engines after injector replacement because they got in a hurry. take your time and you should be ok.

 

[MolaKule]

Originally Posted By: zorobabel
Lets say you do a piston soak on a 2L 4 cylinder engine.
After the soak is done (assuming liquid is still pooling on top the pistons), the engine is slanted so the liquid pools to one side and the liquid is vacuumed out using 1/4" tubing. Little liquid is left pooling on the slated piston tops. Do you think this is enough to hydrolock the engine?
I've seen it mentioned to crank the engine after the soak with plugs, coils and injectors removed/disconnected; I've done that once and I got some mist out, but I wonder if it is really necessary.


Always clean the plug wells to remove any crud before removing plugs.

Always remove all the plugs when doing a soak (preferably overnight, and moving the crank by hand a couple of times).

After a soak, it is always a good idea to siphon out as much liquid as possible.

Cranking the engine with plugs still removed helps to expel any liquid not siphoned and avoids hydrolock.

LCD's, LC20 is still my favorite piston soak liquid.

 

[LeakySeals]

Whatever you put in is going to seep past the rings over time. If you are concerned just wait a day. Most if not all will be gone.

 

[zorobabel]

Thanks for the replies and tips!
I was hoping for a clear answer or at least a post from someone that started the engine after a soak and vacuum without cranking the plugless engine first.