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Yanmar Diesel Service Marathon Generator Post 1
This will be first post of two.
I had two freeze/casting plugs weeping on Yanmar 4 cylinder. I contacted Yanmar and order all parts from the manuals which were provided by me and posted to the PC site. I hired BCI Equipment out of San Antonio to come out to the house and do several critical things on Yanmar motor while I did several other things to cooling system installed by Marathon.
The generator has 3900 hours on it and I have all the service records from previous two owners. There were no services other then oil changes and filters by any owner until now. One service that is in the books is to check valve lash at 2000 hrs and torque head bolts down.Never done….
A key sign your going to have problems is when you see coolant weeping from casting plugs and water pump. What a mess once we drained coolant and pulled the plugs. One of the water pump parts had started to show signs of galvanic corrosion and broke during re-installation. Had new part overnighted in by Yanmar and is here …more on that in next post.
The engine coolant had color but looked used when we drained the block. But the coolant in the Marathon installed radiator looked like mud. Flush the radiator four time with garden house until clear. The Thermoid 7910 1 -1/4 Bellowsflex lines did not come off easy they were 1999 vintage and hardened. I order thirty feet of new Thermoid Bellowsflex from company in Kentucky with date code 2019.
I had to carefully cut the old hoses off with die grinder. To put the new hoses on Marathon radiator in center mof coach I needed to run a wheel with 60 grit sandpaper on the inside of hose to get it to slip on (with grease) without a struggle. Between BCI Equipment working the motor and me working the hoses and cleaning up radiator parts we started a 7:30 and finished at 2:30.
More to come….
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4 Replies
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Great article and good information. Looking forward to your update.
PJ
PS Howdy fellow Texan
2000 Featherlite H3-45
2024 Jeep Grand Cherokee
Leesburg, FL -
Agree – Very Good Post, Ed, and hope you have since made final progress.
How far off was the valve lash?
Please let us know what all you replaced, etc.
Also, any idea what caused the leaking freeze plugs?
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Update:
Valve lash was per specification in Yanmar Maintenance Manual. Motor has 4000 hours on it now. This should have been done at 2000 hours.
The corrosion was caused by not flushing the cooling system and keeping up on SCA’s. The steel Yanmar freeze plugs on 1 and2 cylinders were extremely corroded.
The generator had no service records on it from previous two owners other then oil changes and belts. I had put this off until this year after purchase in 2018.
When we change the casting/freeze plugs we used brass….that turn out to be a problem. The brass plugs are very good but your installation technique has to be spot on. Steel is more forgiving. So we went back to the steel Yanmar casting plugs.
Drove to jobsite here in St Charles Louisanna and had generator temps 155 to 158 F.
Moral of story if you have a 20 year old generator and no history of critical maintenance. Be prepared to spend some money to
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Thank you for that update, Ed.
Glad all is back up and running. Everything is a learning experience. Definitely appreciate all the photos you posted!
Am I correct in understanding that valve lash was still proper despite never having been checked / adjusted in 4,000 hours of operation?
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