Yanmar 3gmd Head Gasket Bolt Torque

[F10]

Just replaced the head gasket on my 30 year old Yanmar 3gmd. She is running good. The manual says to re-torque the head bolts after 50 hours of operation. Is this necessary? I am sure it was not done in 1980 when the engine was new. Afraid that if I start messing with the bolts, I could create a problem.

[RTB]

Originally Posted by F10

Just replaced the head gasket on my 30 year old Yanmar 3gmd. She is running good. The manual says to re-torque the head bolts after 50 hours of operation. Is this necessary? I am sure it was not done in 1980 when the engine was new. Afraid that if I start messing with the bolts, I could create a problem.

I have the same (great) engine. Why would you not follow the service manual directions? You can't screw up anything by re-torquing the bolts. Why not make the effort, since I'm sure the engine is pretty important to you? Not sure what they did when the engine was new. Maybe a scheduled maintenance was required back then? Just like with new automobiles....

Ralph

[sailorchic34]

If the head was properly torqued to begin with, it does not need to be retorqued. I have not retorqued my head on my 3gm30f and and have almost 400 hours on it since the rebuild in 2013 during my summer of discontent.

[F10]

Originally Posted by RTB

I have the same (great) engine. Why would you not follow the service manual directions? You can't screw up anything by re-torquing the bolts. Why not make the effort, since I'm sure the engine is pretty important to you? Not sure what they did when the engine was new. Maybe a scheduled maintenance was required back then? Just like with new automobiles....

Ralph

To re-torque the bolts is not extremely difficult, but not easy either. Need to remove the rocker arms and rocker arm shaft (then also need to do a valve adjustment). There are caps on the valve stems so always a chance they could drop down into the block and then that could be a major job to retrieve. The rockers and shaft need to come off as some of the bolt heads are located under this gear. No way to get a socket on the bolt head without removal. My other concern is that by re-torqueing, I could actually break the seal between the head gasket and head and block. The service manual may not always be correct, or may not always give good advice. Now if I re-torque, everything might go well with no problems, or I could wind up damaging something or breaking a head bolt or stud. I could also find that when I tighten the head bolts, no additional torque is needed (maybe others could chime in and tell me what they have found if they did re-torque the head bolts). Just trying to follow the saying "if it ain't broke don't fix it", as with some of my past experiences, I have broken perfectly good gear trying to make it "better".

[F10]

Originally Posted by sailorchic34

If the head was properly torqued to begin with, it does not need to be retorqued. I have not retorqued my head on my 3gm30f and and have almost 400 hours on it since the rebuild in 2013 during my summer of discontent.

Thanks Sailorchic. I did look at your thread on your engine rebuild and it helped me out a lot. My engine had sat for 9 months and even though I had laid it up well on shut down, when I went to start it I said "I better turn the crank by hand to make sure everything is free". Well the engine was seized. Took the head off and found two of the 3 cylinder with rust. Exhaust valves all rusted. Apparently the exhaust head had leaked from its cooling jacket and allowed water to run into the cylinders thru the open exhaust valves. I was able to free the pistons and clean up the cylinders. Had the head machined with new exhaust valve and seals. Put it back together and amazingly she runs better than ever. Seeing how well she runs, I am sure the exhaust valves had corrosion on them for a long time, as before I did the work, starting would take much longer, now she starts in a second. I was very careful torque the head (and cleaning the mating surfaces). Followed the manual exactly on torque values and the 3 stage sequence.