acem Posted October 28 Posted October 28 I am working on a Volvo MD3B marine diesel in a sailboat I bought and need a little advice. It is a three cylinder four stroke mechanical diesel. It's has valves sticking I need to get freed up.. Below is the rest of the story. The sailboat has sat for a few years and the engine has not been started during that time. When I got the boat the engine didn't want to turn but that is not unusual for marine engines. I got my friend, a retired diesel mechanic, to come help me. After a little effort we got it to turn but not a full rotation. It stopped in the same place both directions. We pulled the valve covers off (each cylinder has it's own head) and found one cylinder had both pushrods broken. We removed the broken pushrods. We removed the injectors to make sure it wasn't hydro locked. We lubed the top end with ATF. After working it some, we heard a valve pop up then it turned properly. When it turned, the valves would go down but would stick then pop up later than they should??? We added ATF to the cylinders to soak. Removed the remaining rockers and pushrods. Then rotated the engine several rotations to lube the cylinders. Obviously I need two pushrods. But the sticking valves are concerning. We believe they are what caused the broken pushrods. I have never had a problem with sticking valves. What causes sticking valves? What is the fix for sticking valves? What else do I need to consider? Quote
dale560 Posted October 28 Posted October 28 43 minutes ago, acem said: I am working on a Volvo MD3B marine diesel in a sailboat I bought and need a little advice. It is a three cylinder four stroke mechanical diesel. It's has valves sticking I need to get freed up.. Below is the rest of the story. The sailboat has sat for a few years and the engine has not been started during that time. When I got the boat the engine didn't want to turn but that is not unusual for marine engines. I got my friend, a retired diesel mechanic, to come help me. After a little effort we got it to turn but not a full rotation. It stopped in the same place both directions. We pulled the valve covers off (each cylinder has it's own head) and found one cylinder had both pushrods broken. We removed the broken pushrods. We removed the injectors to make sure it wasn't hydro locked. We lubed the top end with ATF. After working it some, we heard a valve pop up then it turned properly. When it turned, the valves would go down but would stick then pop up later than they should??? We added ATF to the cylinders to soak. Removed the remaining rockers and pushrods. Then rotated the engine several rotations to lube the cylinders. Obviously I need two pushrods. But the sticking valves are concerning. We believe they are what caused the broken pushrods. I have never had a problem with sticking valves. What causes sticking valves? What is the fix for sticking valves? What else do I need to consider? You are going to have to work that valve up and down a bunch. Sometimes they loosen from the rust if you have injector out you can turn engine up to that piston tdc and down a bit this will keep valve from dropping in. I would shoot penetrating oil onto stem and tap it with spring hooked up a lot of times. They can gouge the guides though and that would require head removal to machine guides. If piston is up you might take valve spring off for more travel to work rust out but don’t drop it on. 1 Quote
New Englander Posted October 28 Posted October 28 I don't know if there's any way to do this on a diesel. Lycoming aircraft engines develop morning sickness where valves stick a bit when cold but operate okay once warmed up. If not addressed the valves stick farther open until eventually hit by a piston with bad consequences. The fix is to push the valve all the way into the cylinder and grab it with a pickup tool. That lets you run a reamer through, clean up the guide, and get the valve back in. Of course you have two 18mm spark plug holes to work through so I doubt there's any way to do it on a diesel. It's carbon and lead deposits that stick aircraft valves and may just some rust on the boat diesel. Maybe if you can't get them free pull the manifolds and look and maybe do the airplane engine trick but grabbing the valve through the ports. Gasket set can't be that expensive and if it's ugly you'll have it to pull the offending head. I've heard those Volvo auxiliary engines are reliable. Happy sailing! 1 1 Quote
dale560 Posted October 28 Posted October 28 2 hours ago, New Englander said: I don't know if there's any way to do this on a diesel. Lycoming aircraft engines develop morning sickness where valves stick a bit when cold but operate okay once warmed up. If not addressed the valves stick farther open until eventually hit by a piston with bad consequences. The fix is to push the valve all the way into the cylinder and grab it with a pickup tool. That lets you run a reamer through, clean up the guide, and get the valve back in. Of course you have two 18mm spark plug holes to work through so I doubt there's any way to do it on a diesel. It's carbon and lead deposits that stick aircraft valves and may just some rust on the boat diesel. Maybe if you can't get them free pull the manifolds and look and maybe do the airplane engine trick but grabbing the valve through the ports. Gasket set can't be that expensive and if it's ugly you'll have it to pull the offending head. I've heard those Volvo auxiliary engines are reliable. Happy sailing! Never thought about grabbing it through exhaust hole and putting it back in place. Learn something new every day 2 Quote
Cattech Posted October 28 Posted October 28 I'm guessing corrosion as well as others above eluded to. The dropping a valve into the cylinder and then refitting it in place is an interesting concept. I have accidentally lost a valve down the guide and have had the end of a borescope fall off down an injector hole. Retrieving said items easier said than done. In your case, put the piston of the offending cylinder at TDC. Remove the valve springs and valve seals. Get the valves somewhat free, then grab the stem with a drill - spin the valve in the guide while spraying some penetrating oil down the guide. Now, it's completely possible that you can free the valves in their guides, but I would be concerned that one or both had been stuck open and have been hit by the piston while getting the engine free. Depending on piston crown shape and/or carbon buildup, this could have bent the stems on these valves. So after freeing them up and getting the seals and springs back on, you should pressurize the cylinder with a rubber tipped blow gun down the injector hole to make sure they are sealing. 1 1 Quote
CIHTECH Posted October 28 Posted October 28 Added heavy exhaust valve springs to an 8.3 Cummins in preparation for an exhaust brake. Done the job with overhead spring compressor by firing order. Due to whatever interruption I forgot to turn engine for the next cylinder. Dropped a valve down in the cylinder, was able to "find" end of valve with a magnet and pull back up thru guide. Couldn't pull it all the way up thru without overcoming the magnet, so next try once I got it started was able to "push" it up thru with piston. 2 Quote
New Englander Posted October 29 Posted October 29 17 hours ago, Cattech said: spin the valve in the guide Here's some spinning I've done on Continental engines. Lycoming exhaust valves are sodium filled and run cooler as they transfer heat up through the guide while Continental valves are not sodium filled and transfer heat solely through the seat. Lycomings stick due deposits, Continentals tend to burn. Continental requires a borescope inspection at each inspection and, if an asymmetrical heat signature is caught early enough, the valve can be lapped in place and continued in service. I've done it both successfully and unsuccessfully. The successful ones saved a lot of time and money. Of course with a diesel there's no nice big spark plug holes like an aircraft engine. Mike Bush sort of pioneered the procedure and filmed it here. He used a rope to hold the valve up to remove the keepers but I found out years ago that shop air pressure would do it. Back in the '70s Continental had a procedure to ream valve guides in place and we did it on the affected batch of engines that were on new Barons and Bonanzas that were delivered. 1 Quote
searcyfarms Posted October 30 Posted October 30 ive got a 6.7 cummins sitting on a pallet in my shop if you dont get that running you can put it in there - its def free its a 2011/12 😁 Quote
acem Posted October 30 Author Posted October 30 56 minutes ago, searcyfarms said: ive got a 6.7 cummins sitting on a pallet in my shop if you dont get that running you can put it in there - its def free its a 2011/12 😁 That probably won't fit but thanks! 3 cylinder 100 cubic inches 30 hp vs 6 cylinder turbo 409 cubic inches. What could go wrong!?!? 2 Quote
Powered by IH Posted October 30 Posted October 30 1 hour ago, searcyfarms said: ive got a 6.7 cummins sitting on a pallet in my shop if you dont get that running you can put it in there - its def free its a 2011/12 😁 Have you ever considered buying a P-pump conversion kit for it? Quote
searcyfarms Posted October 30 Posted October 30 32 minutes ago, Powered by IH said: Have you ever considered buying a P-pump conversion kit for it? i didnt know that was possible with all the electronics on a 6.7 Quote
Powered by IH Posted October 30 Posted October 30 1 hour ago, searcyfarms said: i didnt know that was possible with all the electronics on a 6.7 It was also a suprise to me when I first heard about it, but yes it is possible. Google Search Quote
New Englander Posted October 30 Posted October 30 8 hours ago, acem said: That probably won't fit but thanks! 3 cylinder 100 cubic inches 30 hp vs 6 cylinder turbo 409 cubic inches. What could go wrong!?!? Tim the Tool Man Taylor! 1 Quote
searcyfarms Posted October 30 Posted October 30 8 hours ago, Powered by IH said: It was also a suprise to me when I first heard about it, but yes it is possible. Google Search i do not see the benefit, cost is in the 15 to 20K range for conversion from what i am seeing - i will get rid of it the way it sits im not smart enough to figure out how to get it to work in a non dodge project and finding a 2011/12 that has a body that is worth a toot with a bad engine has not been very findable Quote
Powered by IH Posted October 31 Posted October 31 13 hours ago, searcyfarms said: i do not see the benefit, cost is in the 15 to 20K range for conversion from what i am seeing - i will get rid of it the way it sits im not smart enough to figure out how to get it to work in a non dodge project and finding a 2011/12 that has a body that is worth a toot with a bad engine has not been very findable I know, it's not even worth it unless you are looking to make big ponies out of a Cummins. On the flip side, I did find this on a quick Google search if you were interested, it's in TX and it supposedly has a clean title, selling because of "Mechanical Damage". Maybe it ate the grid heater bolt? It's definitely a project though. https://www.copart.com/lot/74450056/clean-title-2012-dodge-ram-3500-st-tx-lufkin I don't blame you though if you're not interested, was just curious to see if there actually was anything on Google with a bad motor for sale. I also think the KBB value is a little generous. Quote
Powered by IH Posted October 31 Posted October 31 38 minutes ago, searcyfarms said: Awwwww nutz its an auto That doesn't mean anything...😄 https://www.facebook.com/share/1Do9jVVoz1/ Sorry @acemfor hijacking your thread. Quote
Binderoid Posted October 31 Posted October 31 On 10/30/2026 at 8:01 AM, searcyfarms said: i do not see the benefit, cost is in the 15 to 20K range for conversion from what i am seeing - i will get rid of it the way it sits im not smart enough to figure out how to get it to work in a non dodge project and finding a 2011/12 that has a body that is worth a toot with a bad engine has not been very findable It is every penny of that..... just did that on R62 Gleaner.... with the added benefit of the combine monitors not being able to read the engine functions and beeps and 'fails' constantly. On our own trying to work this out as Cummins and Gleaner have parted ways and no tech support is available. 1 Quote
acem Posted October 31 Author Posted October 31 I'm having trouble finding used pushrods this side of the pond. New ones are available but will be about $150 each delivered. I have a hard time spending that on an engine I have never heard run. They are solid pushrods. I'm considering making a pair in my lathe to get her running. Anyone ever make a pushrod? Quote
CIHTECH Posted October 31 Posted October 31 Just now, acem said: Anyone ever make a pushrod? I needed a set for a little 2022 NH tractor a guy ran in creek. Not available thru CNH, had some custom built and ordered thru Summit IIRC.... 1 Quote
Cattech Posted October 31 Posted October 31 2 hours ago, acem said: I'm having trouble finding used pushrods this side of the pond. New ones are available but will be about $150 each delivered. I have a hard time spending that on an engine I have never heard run. They are solid pushrods. I'm considering making a pair in my lathe to get her running. Anyone ever make a pushrod? Being solid and not gun drilled, and since it is to get the engine running and verify that the thing isn't shot in other ways, I don't see why not. Or maybe a person could take a good rod to a equipment salvage yard and match it up to something that would be close enough? I would consider any substitute push tubes temporary, once you know the engine is good, I would consider it prudent to bite the bullet on the proper parts. 2 Quote
jeeper61 Posted October 31 Posted October 31 2 hours ago, acem said: I'm having trouble finding used pushrods this side of the pond. New ones are available but will be about $150 each delivered. I have a hard time spending that on an engine I have never heard run. They are solid pushrods. I'm considering making a pair in my lathe to get her running. Anyone ever make a pushrod? Might be possible if they a spherical at both ends if it has a cupped end then not so easy What's the part number? I see some on E-bay 1 Quote
New Englander Posted October 31 Posted October 31 On 10/27/2026 at 9:25 PM, acem said: I am working on a Volvo MD3B marine diesel in a sailboat I bought and need a little advice. It is a three cylinder four stroke mechanical diesel. It's has valves sticking I need to get freed up.. Below is the rest of the story. The sailboat has sat for a few years and the engine has not been started during that time. When I got the boat the engine didn't want to turn but that is not unusual for marine engines. I got my friend, a retired diesel mechanic, to come help me. After a little effort we got it to turn but not a full rotation. It stopped in the same place both directions. We pulled the valve covers off (each cylinder has it's own head) and found one cylinder had both pushrods broken. We removed the broken pushrods. We removed the injectors to make sure it wasn't hydro locked. We lubed the top end with ATF. After working it some, we heard a valve pop up then it turned properly. When it turned, the valves would go down but would stick then pop up later than they should??? We added ATF to the cylinders to soak. Removed the remaining rockers and pushrods. Then rotated the engine several rotations to lube the cylinders. Obviously I need two pushrods. But the sticking valves are concerning. We believe they are what caused the broken pushrods. I have never had a problem with sticking valves. What causes sticking valves? What is the fix for sticking valves? What else do I need to consider? A little googling says it’s not uncommon. I think if you get the sticking valves to move I would straighten the pushrods out, see if it runs, then pull the head and fix it right. No sense in running out of wind and having an inoperative aux or trying to dock with no engine. 1 Quote
iowaboy1965 Posted October 31 Posted October 31 There are places that custom make pushrods. I know in the ford fe world I see mention of measuring to have new made, and several places are talked about that make them. How pricey they are I would have no idea 1 Quote
just Dave Posted October 31 Posted October 31 I would think they are similar in column strength to a shock absorber rod. The are a very good source of chrome rod in metric sizes, and often just thrown out. 1 Quote
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