Yanmar engine 4HJ3-E 1997 8600 hours is blocked

[Fletcher7]

Hello there. My SO 42.2 with Yanmar 4HJ3-E , has the engine blocked. The front dumper can be moved by hand, clockwise and counterclockwise for half way a turn in each direction, and then get blocked. Would anyone had this kind of problem ? Thank you to all of you folks. Fletcher.

[skipperpete]

Originally Posted by Fletcher7

Hello there. My SO 42.2 with Yanmar 4HJ3-E , has the engine blocked. The front dumper can be moved by hand, clockwise and counterclockwise for half way a turn in each direction, and then get blocked. Would anyone had this kind of problem ? Thank you to all of you folks. Fletcher.

Hi Fletcher, my best guess is a dropped or bent valve or valve seat, that would explain the ½ turn rotation and then locked. It could also be a number of other things depending on the events leading up to the partial lockup so a bit more information would be helpful.

[Fletcher7]

Your message is really clear. I was thinking about other possibilities, as timing gear broken teeth, but the sound I heard when this happened was so hard-hitting, I'm quite sure you are right. This happened when I start the engine, usually, it starts at once, but this time, when I turned the key, it did not start, it was turning too slow, then I put more gaz, and it starts making a terrible noise. I stopped straight ahead. Should more infos help you, I will be please to inform you. Thank you so much Skipperpete. Paul.

[skipperpete]

Ok, that changes the possibilities, it might have been a hydrolock resulting in a bent conrod. Is there any chance that water was able to get into the cylinders? I thought about maybe the starter motor being jammed but the amount of free rotation would be way less than ½ turn either way. Same with the timing gears ...... and I’ve never actually seen a stripped gear on any of the Yanmar’s. Timing belts on other engines ( Volvo MD22, Perkins M50 ) do break,usually with considerable damage.
If your engine has hydrolocked it’s important to stop any corrosion from damaging the other cylinders.
Pete.

[Fletcher7]

Let me explain you how things did happen. The heat exchanger, 25 years old, both round aluminum front and rear taps where almost getting corroded, so I bought a new Yanmar unit. I was planning to install it. In the morning, I did start the engine, no problem, and let it warmed up about one hour, to be confortable in unscrewing the unit. The engine started and worked perfect .I removed all cooling and see water, disconnect exhaust elbow and pipe, no water in exhaust .I did removed old exchanger and did installed new one, then refilled cooling and open engine sea water valve. Cylinder head is about 60 cm higher than exhaust elbow and pipe .Hydrolock is in his right position and is always operational . First I also thought about water in cylinder, then I switch on something else than water that could have avoid exhaust valve to close properly and than be hit by piston. I also unscrewed all rocker arms and all the valves are on the same level. The noise I heard when I started the engine was a full cling-cling metal against metal.
Ok, thank's again Pete, Paul.

[Celestialsailor]

I had this happen to my Westerbeke W-46, in my prior boat (Hallberg Rassy 35). Accept it rotated about 350 degrees before doing that. Turned out the boat had sat from the prior owner in the slip and the engine started once a month for 5 minutes and never warmed up. Carbon accumulated in the cylinder head. Then the owner passed away and the boat sat for another couple of years. With moisture in the air, the carbon swelled and since there is very little clearance between the piston and head, it caused a lock up when cylinder 4 tried to achieve TDC.

[Fletcher7]

Hello Celestialsailor.
Thank you for your message.
Nice Hallberg Rassy 35, my best friend has one.
I have my SO 42.2 in a port in Bastia Corsica for almost 4 years. During winter, I usually make the engine run at least once a month, and let it warm up for about 3/4 of hour.
Temperature does stabilize at 75 celsius.
This time, I had to replace heat exchanger by a new one. In the early morning I started the engine and let it run for about one hour, I wanted it to be warm so I could unscred exchanger bolts easily . And it when I restart it that the mess happened.
Thank you, Paul.

[skipperpete]

Celestialsailor definitely has a point, I once saw this happen with a small diesel generator and the space between the piston and the head was full of carbon. I’m very interested in what caused this lockup and I think the next step might be to lift off the cylinder head.

[Celestialsailor]

Fletcher7 stated that the engine rotates a 1/2 a turn. So I don't think it is the same problem I had with my Westerbeke unless he is mistaken about how far it turns. That said, it is something simple but where to start?

Many moons ago, I was a motorcycle mechanic. When a customer brought his broken bike in, I would ask what the last thing he had done to the bike. Most of the time, what was previously worked on was incorrect and easily repaired. So I am wondering if the heat exchanger was removed if the engine would turn over indicating a fastening bolt in the wrong place perhaps.

[Stewie12]

I would agree that the next step is to take the head off and take a look

[bil56]

valve spring broken ? broken or bent valve?

first, take the head cover off >???
then take the head off > ???

:-(

[Boatyarddog]

Originally Posted by Fletcher7

Hello there. My SO 42.2 with Yanmar 4HJ3-E , has the engine blocked. The front dumper can be moved by hand, clockwise and counterclockwise for half way a turn in each direction, and then get blocked. Would anyone had this kind of problem ? Thank you to all of you folks. Fletcher.

A lot of guessing going on here,
You sure it's even engine related?
Broken damper plate can interfere with rotation as well.
We should try to avoid all the worst case senerios.
Focus on the simpler problems first, rule them out.
The rotational issues should be straight forward.
Broken Flywheel teeth, bolt let loose is blocking rotation in the flywheel housing.
I'd remove the injectors first to look for Hydroloc.
Then the starter, look for damage attempt to rotate by hand.
If there's not anything visible here, digging deeper will be a commitment.
Boatyarddog

[Boatyarddog]

Originally Posted by bil56

valve spring broken ? broken or bent valve?

first, take the head cover off >???
then take the head off > ???

:-(

I don't think there's valve to piston contact.
If you removed the valve train at the top and they all looked even, your good there.
I'd continue with the valve train removed, and rotate by hand.
Remove the starter, look for problems here.
Internal problems would be last.
Boatyarddog

[Boatyarddog]

Originally Posted by Stewie12

I would agree that the next step is to take the head off and take a look

Nope, a boroscope, will save you lotsa time and un nessessary work.
It's worth a rental for one.
Boatyarddog

[skipperpete]

Originally Posted by Fletcher7

Hello Celestialsailor.
Thank you for your message.
Nice Hallberg Rassy 35, my best friend has one.
I have my SO 42.2 in a port in Bastia Corsica for almost 4 years. During winter, I usually make the engine run at least once a month, and let it warm up for about 3/4 of hour.
Temperature does stabilize at 75 celsius.
This time, I had to replace heat exchanger by a new one. In the early morning I started the engine and let it run for about one hour, I wanted it to be warm so I could unscred exchanger bolts easily . And it when I restart it that the mess happened.
Thank you, Paul.

Hi again Paul, I suggest that this problem is related to the changing of the heat exchanger. The hydraulic lock seems to me to be the prime suspect BUT if seawater didn’t come from the exhaust aqualock via siphon past a faulty vent loop or overcranking then the only other point of entry is from the fresh/ coolant side via a faulty or porous casting or a crack in the tubestack housing through to the exhaust ports ( 4mm thick in this area)
Also the possibility of carbon buildup in the exhaust ports and valve stems being dislodged and falling into the cylinder via an open valve is still something to consider.
Pete.