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How much liquid is needed to hydrolock an engine? #4674266
02/22/18 11:14 AM
02/22/18 11:14 AM
Joined: Jan 2011
Posts: 664
Anaheim, CA
zorobabel Offline OP
zorobabel  Offline OP
Joined: Jan 2011
Posts: 664
Anaheim, CA
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.


1997 Maxima 192k, QSGB 5w30+QSUD 5w30 (2:1), PL14477
2004 Corolla 195k, VWB 5w20 + SSS 10w40, MGL4967
Re: How much liquid is needed to hydrolock an engine? [Re: zorobabel] #4674272
02/22/18 11:20 AM
02/22/18 11:20 AM
Joined: Jan 2013
Posts: 2,265
Texas
WyrTwister Offline
WyrTwister  Offline
Joined: Jan 2013
Posts: 2,265
Texas
Do not know if it is necessary , but that is pretty much what I would do .


Wyr
God bless
Re: How much liquid is needed to hydrolock an engine? [Re: zorobabel] #4674277
02/22/18 11:23 AM
02/22/18 11:23 AM
Joined: Dec 2006
Posts: 8,464
Illinois
mrsilv04 Offline
mrsilv04  Offline
Joined: Dec 2006
Posts: 8,464
Illinois
I'd crank it with the plugs out, just for the peace of mind. Then you know.


2004 Silverado - on its 3rd Jasper engine in less than one year.
Re: How much liquid is needed to hydrolock an engine? [Re: zorobabel] #4674278
02/22/18 11:23 AM
02/22/18 11:23 AM
Joined: May 2009
Posts: 12,304
N.H, U.S.A.
ARCOgraphite Offline
ARCOgraphite  Offline
Joined: May 2009
Posts: 12,304
N.H, U.S.A.
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.

Last edited by ARCOgraphite; 02/22/18 11:24 AM.

2019 VW Jetta S,6M OCI#0 62mi-Castrol Edge Prof VW508+OE Filter; '17 Subaru Crosstrek CVT OC#5 37K mi-SOA/Idemitsu 0w20 + SOA Filter
Re: How much liquid is needed to hydrolock an engine? [Re: zorobabel] #4674289
02/22/18 11:26 AM
02/22/18 11:26 AM
Joined: Feb 2017
Posts: 27
Tennessee
RLS Offline
RLS  Offline
Joined: Feb 2017
Posts: 27
Tennessee
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.


Robert - Retired Fleet supervisor and x-drag racer
Current Competitive shooter and trainer.
Re: How much liquid is needed to hydrolock an engine? [Re: zorobabel] #4674323
02/22/18 11:45 AM
02/22/18 11:45 AM
Joined: Jun 2002
Posts: 19,611
Iowegia - USA
MolaKule Offline
MolaKule  Offline
Joined: Jun 2002
Posts: 19,611
Iowegia - USA
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.


Scars remind us of where we have been, but do not have to dictate where we are going.
Re: How much liquid is needed to hydrolock an engine? [Re: zorobabel] #4674582
02/22/18 03:07 PM
02/22/18 03:07 PM
Joined: Feb 2011
Posts: 6,845
Hudson, NH
LeakySeals Online content
LeakySeals  Online Content
Joined: Feb 2011
Posts: 6,845
Hudson, NH
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.


06 Escalade 6.0L LQ9 AWD 165k M1 0w40
03 Maxima 3.5L POS 152k ST HM 10w30
Re: How much liquid is needed to hydrolock an engine? [Re: zorobabel] #4675442
02/23/18 12:12 PM
02/23/18 12:12 PM
Joined: Jan 2011
Posts: 664
Anaheim, CA
zorobabel Offline OP
zorobabel  Offline OP
Joined: Jan 2011
Posts: 664
Anaheim, CA
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.

Last edited by zorobabel; 02/23/18 12:23 PM.

1997 Maxima 192k, QSGB 5w30+QSUD 5w30 (2:1), PL14477
2004 Corolla 195k, VWB 5w20 + SSS 10w40, MGL4967

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