Oil leak

For the last several years we have had a nuisance oil leak. At first we would loose about 1/2 quart per 100 hours, however over the last two years it has increased to one gallon per 100 hours. It became a pain in the backside to keep clean. I feared it was the rear seal leaking. The engine in question is a Ford Lehman 120 with 7k hours and made in 1980, so this Fall the admiral and I decided to fix the problem. I called Brian at American Diesel and discussed the procedure and possible problem. He indicated that it was highly unlikely that the rear seal was the issue despite the age of the engine. I found a mechanic who willing allowed me to help him with the project. He felt it would not be a difficult job. Day one the transmission, shaft, damper plate and flywheel were removed time 2.2 hours. Pictures to follow. Two 4 X 4’s with come alongs were used, one lifted the transmission out of the way and the other hooked to the lifting eye of the engine supported the back of the engine. It was obvious the leak was from the soft plug in that the red RTV failed. We also employed a mirror to view the underside of the rear seal , bone dry. Parts ordered along with a new damper plate. After parts received another 3 hours to reinstall everything back to original. Total cost $1200 for labor and parts plus express shipping to Alaska.

Someone takes pride in their engine room and machinery. Very nice.

That sure looks like a coolant freeze plug. Fooled me.

Thinking along those lines too.

Soft plug for oil pressures exceeding 80psi? But Im no engine guy.

Thanks for posting. As chronic DIYer I love seeing other people's adventures in maintenance. #EngineRoomGoals

chriscritchett said:

Someone takes pride in their engine room and machinery. Very nice.

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Agreed, I wish everything was clean like that in mine!
One question, is this a common practice to put a sacrificial anode on the shaft inside the boat?

L

What was the condition of the damper plate at 7k hours? Mine on a pair of BW Velvet drives have >6k, so I am curious.

Lou_tribal said:

Agreed, I wish everything was clean like that in mine!
One question, is this a common practice to put a sacrificial anode on the shaft inside the boat?

L

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The anode on the shaft inside the boat is to keep the shaft from sliding completely out in case of shaft or coupler failure.

Ken

A few years ago the shaft released itself from the transmission as I was backing up. The shaft slid back and stopped at the rudder. The zinc is to prevent the shat from slipping to far. Old trick I learned from a fisherman.

The damper plate springs showed wearing as well as being loose compared to the new one.

Gbinterim said:

For the last several years we have had a nuisance oil leak. At first we would loose about 1/2 quart per 100 hours, however over the last two years it has increased to one gallon per 100 hours. It became a pain in the backside to keep clean. I feared it was the rear seal leaking. The engine in question is a Ford Lehman 120 with 7k hours and made in 1980, so this Fall the admiral and I decided to fix the problem. I called Brian at American Diesel and discussed the procedure and possible problem. He indicated that it was highly unlikely that the rear seal was the issue despite the age of the engine. I found a mechanic who willing allowed me to help him with the project. He felt it would not be a difficult job. Day one the transmission, shaft, damper plate and flywheel were removed time 2.2 hours. Pictures to follow. Two 4 X 4’s with come alongs were used, one lifted the transmission out of the way and the other hooked to the lifting eye of the engine supported the back of the engine. It was obvious the leak was from the soft plug in that the red RTV failed. ...

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Like 2 others I see a silver colored metallic looking plug they call a "freeze plug" (here called a "welch plug"). Though I think those plugs usually open into coolant chambers.
What do you mean by "the red RTV failed"? Where is "the soft plug" located?

kchace said:

The anode on the shaft inside the boat is to keep the shaft from sliding completely out in case of shaft or coupler failure.

Ken

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Gbinterim said:

A few years ago the shaft released itself from the transmission as I was backing up. The shaft slid back and stopped at the rudder. The zinc is to prevent the shat from slipping to far. Old trick I learned from a fisherman.

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Clever idea, thank you both for the info

L

The plug closes the end of the camshaft bore. The hole is there from the block machining process, and the plug is installed to keep oil from the rear cam bearing from escaping.

BruceK, av8r explains correctly the function of the silver plug, it does not have anything to do with coolant. RTV is a coating that is placed on the edge of the silver plug which forms a gasket to prevent the oil from leaking out.

Thanks guys, knowing FL potential issues could come in handy one day.

BruceK
Should not be an issue to worry about. The red RTV sealant would indicate a repair or reassembly probably using an incorrect plug, like maybe a NAPA freeze plug in an SAE size instead of the corrrct English Ford size. If yours isn't leaking it probably won't leak in the future.

This is an update to the results of the repairs. First of all the oil drip via the starter motor is nonexistent. I also removed the fuel pump and placed a new gasket with RTV to prevent any oil leaks. This area is a prime offender of oil leaks as the bolts tend to loosen from the vibration of the motor. The damper plate made a huge difference in that the sound of rattling bolts has been eliminated and the shifting action is nice and smooth. Definitely a worthy winter project.

Gbinterim said:

The damper plate springs showed wearing as well as being loose compared to the new one.

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When I rebuilt my two engines, I cleaned them, painted with gray primer, then I dipped those damper plates in gear oil. Then let them drip off. These things have springs and they move around the shaft a little. I have Palmer 392 IH engines and was not sure I could ever replace them, but I found by looking at google images, a detroit diesel uses the same damper plate. Mine were in good condition even as old as they are from 1970. They were greasy which likely helped them survive.

Idle rattle/chatter is a big destroyer of the dampner plates that use springs from my research.

On mine you could clearly see metal fatigue failure ....... rust was present but minor.