Water in a cylinder

R

Rick_D

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Jul 10, 2022
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34740
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Hi all.

Last season when I pulled to do a compression check I noted that one of my cylinders ejected some water. Not a lot but more than none which is a problem. Ran the engines and they seemed ok. When winterizing that cylinder again ejected a bit of water. Thought it was gas at first but it had no smell.

Theses engines are less than 10 hours old. Compression check revealed every cylinder right around 165lbs including the suspect one. So I assumed the head gasket was no the issue. So what does that leave?…manifolds and elbows are new but I pulled them yesterday to look for any indication of leakage and I saw none.

Anyone have thoughts on possible causes and best way to troubleshoot this?

—Rick
 
Cracked head? In any case don’t let any water stand in there as it will damage the rings, cylinder etc. at least put some diesel in the cylinder to keep it lubricated until you can do more
 
Just looked at the exhaust manifold and two of the exhaust ports that would correspond to cylinders 6 and 8 show rust discoloration in the manifold while 2 and 4 cylinders are just the usual black exhaust soot
 
PascalG said:
Cracked head? In any case don’t let any water stand in there as it will damage the rings, cylinder etc. at least put some diesel in the cylinder to keep it lubricated until you can do more
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When I winterized it I poured a decent amount of mm oil in all the cylinders and then circulated it. Cracked head…wouldn’t that affect compression? Compression matched the other cylinders just fine.
 
Rick_D said:
Just looked at the exhaust manifold and two of the exhaust ports that would correspond to cylinders 6 and 8 show rust discoloration in the manifold while 2 and 4 cylinders are just the usual black exhaust soot
Click to expand...
Which cyl was ejecting water?
Believe it or not you can have normal compression test readings, and have a head gasket leak that lets water in a cyl especially after the engine runs and it cools off a bit. Sometimes the leak is not at the point that will cause it to leak under compression but as the engine cools off, it allows water from a water passage into a cylinder. I had this on my old 4.3 a few years after a bad overheat. While this was confusing to me, when I took the heads off and inspected the head gaskets the cause was obvious. When you say the engines are less then 10 hrs old, are they brand new, or remans? If reman, who did them?
Does the exhaust system have a wet joint design (like older Mercs and all Volvos) or dry joint like late model Mercs? If it is dry joint then leaks from the exhaust are very unlikely.
 
Cylinder 6... 3rd from the front on the right hand side.
Engines are remans from 800RunsNew.
Exhaust type...I think it's wet....the coolant water is forced up from the bottom of the manifold up into the elbow where it mixes with the exhaust. Is there any test that can be performed now to further isolate the issue before the intake manifold and head come off? The fact that the exhaust manifold had only 2 ports with rust in them makes me lean towards thinking that it's not the elbow that's faulty or all the exhaust ports would show water. So that narrows it to the manifold or as suggested, the head itself.
 
What happened to the previous motor, which made you replace it? Reman short block, long block, or entire motor? This is a sea water cooled motor, right?

I believe it has to be either water from the cooling circuit - via crack in the head, block, intake manifold, or gaskets - or exhaust water getting sucked back through the valves because of defect on the exhaust side - manifolds, risers or gaskets. Also possible that whoever assembled the motor did not properly seal a bolt that goes into the water jacket - several of the head bolts, and I believe some or all of the exhaust & intake bolts (depending on which size & generation block you have) require thread sealant.

I suggest a leak down test, on the wet cylinder, and each side of it. That may reveal the problem.
 
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What you could do is remove the exhaust manifold and elbow together in one piece (careful, heavy). Then prop it up level and hook up a water hose to the feed hose. Run water through the hose, and watch what happens inside the exhaust ports that mate up with the cyl head. If you find a trail of water right at the exhaust port for that #6 cyl then you got lucky. It can depend on the angle of the engine as it sits in the boat.
Back in September 2021 I had the exhaust manifolds off of my engine to get clearance for replacing the power steering actuator (not a fun job). Since they were off I tested them that way and they were fine. Normally here in salt water we change the elbows at least every 5-7 seasons.

If that's not it, then what I'd do next is replace the hoses feeding the manifolds with clear hose temporarily. Run the boat in the water til the engine warms up and the thermostat is open. If you see bubbles in the water exiting the thermostat housing, that is a sign that exhaust gas is getting into the cooling water, and conversely, that will also allow water into a cylinder depending on where the problem is. If you find that, I'd be calling the place you got the engines from (warrantee)?
 
I did in fact test the manifold and elbow for 24 hours but they did not leak. The problem ended up being the rocker cover gasket was not in place along the top edge from when I last took the cover off. With the intake manifold already off I decided to pull the head anyway to be safe. Gasket appeared fine and the head is at a machine now getting checked.
 
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