DIY rebuilding of diesel engine Yanmar 6LY

Genuine vs OEM

Just an update on this rebuild.

The camshaft is in the shop, waiting to be polished.

The crankshaft had a couple of main channels damaged by the corrosion. The shop suggested grinding 0.5mm out to remove those imperfections. There are just a few dips, and one option was to polish and use them as is, but the machinist said those dips would eat new main bearings much faster than a perfectly smooth surface, so i opted for grinding and ordered a new 0.5 US main bearings. It's kind of scary. What if they grind too much? i guess i have to trust other people with my things at some point. There is one more size for main bearings (1.00 US) but i really do not want to order another set.

New sleeves are in the cylinders. I cleaned the sleeves and cylinders with Varsol and brake cleaner until the towels came out clean. I put the sleeves into the freezer overnight and installed them the next morning without much force. I will measure the inside diameters and protrusion to see if they match the specs in the next few days.

Assembled, tested and adjusted injectors came from the shop. At first, they scared me, claiming many Yanmar parts from Asia are fake even if they appear in the original packaging and are sealed. It would be a huge bummer, but later they confirmed new nozzles are genuine Yanmar, so this is good news.

I compared Genuine and "OEM" exhaust valves to see if OEM is truly the same part from the same factory but without Yanmar packaging.
.. short answer - they are not.

Price from this supplier:
119593-11110, EXHAUST VALVE
Genuine from US supplier: $123
Genuine from Asian supplier: $70
OEM from Asian supplier: $20

And there are 6 of them in each engine.
The similar difference for intake valves so, if OEM is usable, it will save a few $$ on the rebuild.

Packaging:


Original:


OEM:


Genuine:


Original:


OEM:


Genuine:


Side view (genuine is on the right):


Front view (genuine is on the right):


so, the OEM is not the same as genuine, and the difference is enough for me not to mess with OEM, but it may work fine with significant cost savings.

I hope it helps someone.

When it comes to valves, metallurgy is just as important as dimension, IMO.
I would trust the Yanmars most for that reason.

I dated a metallurgical engineer. My view of these things is much different than before. It matters.

The crankshaft had a couple of main channels damaged by the corrosion. The shop suggested grinding 0.5mm out to remove those imperfections. There are just a few dips, and one option was to polish and use them as is, but the machinist said those dips would eat new main bearings much faster than a perfectly smooth surface, so i opted for grinding and ordered a new 0.5 US main bearings. It's kind of scary. What if they grind too much? i guess i have to trust other people with my things at some point. There is one more size for main bearings (1.00 US) but i really do not want to order another set.

Click to expand...

I'd be concerned and would question them regarding heat treat. Not from getting the crankshaft too hot but from them grinding into the transition zone.
I have seen a couple of failures in older Perkins diesels from this. All were around 100 ish hours.
I have considerable experience with heat treating automotive camshaft journals and this is similar depending upon how it was originally heat treated.

jleonard said:

I'd be concerned and would question them regarding heat treat. Not from getting the crankshaft too hot but from them grinding into the transition zone.
I have seen a couple of failures in older Perkins diesels from this. All were around 100 ish hours.
I have considerable experience with heat treating automotive camshaft journals and this is similar depending upon how it was originally heat treated.

Click to expand...

Isn't this sort of re-grind routinely done on crankshafts? I know I've had it done numerous times.

Hopefully the shop does a hardness test to determine if the journals are hardened or not before machining.

Hardened cranks in the past were typically found on high performance engines.

It is much more common on modern engines nowadays.

Northern Spy said:

It is much more common on modern engines nowadays.

Click to expand...

Modern engines are all high performance! 100 HP/litre displacement is common now in cars. That was unimaginable not that long ago.

I would never save money on knock off internal parts unless forced to do so. Dropped valve has taken out many engines . Some beyond repair

You're not going to find a crank where the journals aren't hardened

Cast iron cranks found in older engines work harden from the machining and grinding of journals, so were not commonly hardened in the production process.

Forged (and fabricated cranks) require hardening. Most are done with induction treatment. Generally, induction hardening has adequate depth for regrinding and polishing journals. Under 0.020" probably not a concern.

I've never rebuilt an engine with a forged crank. Nodular cast was the fanciest I've seen (Old English sports cars). But have overseen regrinding of journals (not crankshafts) and subsequent hardness testing in industrial environments. Have a pretty good understanding of heat treating and spent a fair amount of money annealing metal (PWHT), but that said, not near as much hardening metal.

jleonard said:

I'd be concerned and would question them regarding heat treat. Not from getting the crankshaft too hot but from them grinding into the transition zone.

Click to expand...

I'll ask the shop about this. They seem to be experienced with hundreds of crankshafts waiting to be worked on in the shop and have very good reviews. Hopefully, they know what they are doing.

This is the only thing I'm waiting for to start assembling the engine.
all other parts were received.

it's going to get as low as -25C/-13F here in a few days and will be pretty refreshing in the garage where I work on the engine. hopefully, the heater will be able to keep it at least above freezing.

Crankshaft and camshaft are still not ready. They promised the end of the week now but showed me a crank which was waiting to be worked on for 18 months so end of the week maybe too optimistic.

Working with the shops was the most frustrating thing in this project so far. I can not imagine what a cluster*uck it would be to have a local shop do this whole rebuild. No competition is the problem.

Anyway, cylinder sleeves are in, all freeze plugs are installed in the head and the block.



Fun fact - some freeze plugs I got are stainless and some are steel - the same 40 mm plugs from the same US supplier. Not sure if you can request ss specifically.

I also did the "valve job", or whatever kids call it nova days.
The valve seats looked fine at first but with some light and magnification, you can see the imperfections.

Before:



A cheap wooden valve tool with rubber suction caps did not work for me - it kept getting unstuck from the new valves even after cleaning everything with alcohol.

I used a drill with a short flexible hose method - 2 seconds clockwise / 2 seconds another way. it does not take much. There are a few youtube videos on how to do that.
I would prefer a manual tool because you can feel exactly when it's done so you do not take out too much material, but we have to work with what we have.

After:

Hallelujah! Engine gods had finally smiled at me, and I got my crank back from the shop.

Check out that forest of cranks in that shop. The owner is a very nice guy; he told me some cranks have been waiting for over 18 months. I got super lucky to get mine in just 3 months





His prices are from 90s. he charged me for polishing my camshaft and grinding the crankshaft less than I was quoted just to polish my crankshaft in another shop. no wonder he has a gazillion of cranks waiting.

I suggested him double the prices, hoping I never had to use his service again (but if I had to, I would gladly pay more to get it done faster). He'll make more money, have less work, and have happier customers who will get this done in a more reasonable time.

Crank just removed from the block:



And here is my beautiful shiny, refurbished crank:



Now, the fun part of getting the beast back together.
Wish me luck.

I congratulate you on starting and doing a job which is well beyond the average shade tree mechanic. It appears to me you are doing everything right.

However..when I had my engine rebuilt by a professional shop they told me the crank met specs but the cam did not. They replaced the cam and gave me the old one, and all the replaced parts. I could not discern the damage on the cam. They must use some pretty sophisticated equipment to determine it was bad. I trust them. There is no way I would have been able to tell it was bad had I done the work myself.

As you near the end of the project it would be nice to see exactly what you have invested in the job. I understand that buying certain tools was expensive but that is part of the job. Also replacing the V-belt pulley was expensive and a professional shop probably would not have broken the original one, but again, it's part of the job.

From what I have seen, you will be near the cost of a professional rebuild. Mine was about $17,000.

pete

Just a thought:
Are you aware that valves are typically ground with a different angle than seats?
This is to provide a superior seal - particularly good in high compression diesels.
The suction cup and grinding paste method is intended for small, cheap engines.
I didn't use that method on my 60 year old 7.5 to 1 C.R. Landcruiser engine and
wouldn't on any diesel.
Before the head goes on talk to the shop that is resurfacing the head (you're
hopefully getting that done) and see what they charge to properly do the valves.

I agree . I did not like your valve job. It is a critical mate and should be done at the machine shop. It’s short money for long life.

Thanks, for the suggestion. I did the valve job according to the Yanmar service manual for this engine. There is a separate section detailing how this has to be done. If some shop do it differently, there is no way to say they do it more "properly" than the manufacturer's recommendation.

I did not change any angles and just cleaned up the seats surfaces a bit. This engine does not have any wear because of the very low hours.
If this was a high hours rebuild, I would have a shop to replace the valve seats.

If there was no wear than why touch them at all? Oh, they had rust and pitting.
Same engine that was immersed in water.
Same engine that needed pistons, rings, liners, injectors and many other parts.
Just out of curiosity, how much $ are you saving by doing your own 'valve job'?

KnotYet said:

Just out of curiosity, how much $ are you saving by doing your own 'valve job'?

Click to expand...

if I were good at saving money, I would buy a kayak instead of a power boat with two massive diesel engines.

I want a good shop to do many things on this engine but i did not find a shop i can trust around here. Most i called did not want to take any smaller work except a complete rebuild which they loosely quoted as "starting from 25k" or they did not work with the engines that big.

One shop looked ok with good reviews but they kept my crank for several weeks, avoiding my calls or telling me "it will be ready in a couple of days" until i came and took it from them. I brought it to a specialized crankshaft shop and it took almost 2 months for them to get to it. I do not want to wait another 2 months to get the valve job.

If someone has a good trusted shop in the area, theoretically, you can dissemble the engine yourself and use the shop to do the partial or full re-work and assembly of the block and the head. it should take a shop just a few days. this was my original plan.

Waterant said:

if I were good at saving money, I would buy a kayak instead of a power boat with two massive diesel engines.

I want a good shop to do many things on this engine but i did not find a shop i can trust around here. Most i called did not want to take any smaller work except a complete rebuild which they loosely quoted as "starting from 25k" or they did not work with the engines that big.

One shop looked ok with good reviews but they kept my crank for several weeks, avoiding my calls or telling me "it will be ready in a couple of days" until i came and took it from them. I brought it to a specialized crankshaft shop and it took almost 2 months for them to get to it. I do not want to wait another 2 months to get the valve job.

If someone has a good trusted shop in the area, theoretically, you can dissemble the engine yourself and use the shop to do the partial or full re-work and assembly of the block and the head. it should take a shop just a few days. this was my original plan.

Click to expand...

Great example of the reality of boating (and other things too). How often do you hear "hire a qualified marine electrician", or "take it to a trusted machine shop". Good luck with that. You might as well try to hire a unicorn who has a bag of pixie dust. And if you do know someone who is good, they are booking jobs in 2024.

Exactly. if you find a good mechanic/machine shop, cherish them as you do your lawyer and your accountant.

C&M Auto Machine shop up the road in Alexandria is one of those old-school
shops run by a couple of older guys that might be what you describe above.

More notes: because you have had the crank reground, measuring its fit in
the new bearings is a subtle but important step. Do some reading, watch a
video and maybe talk to people that do this all the time for some pointers.
Having done this recently, I could offer some advice but mainly don't rush.
You may get everything right the first time but if one or more bearings are
'tight' be prepared to have a few ten-thousandths ground from the crank. In
the case of my Landcruiser rebuild, I made 2 trips back to the crank shop.

I have one word for you: Plastigage! OK, two more words: Assembly lube!

twistedtree said:

Great example of the reality of boating (and other things too). How often do you hear "hire a qualified marine electrician", or "take it to a trusted machine shop". Good luck with that. You might as well try to hire a unicorn who has a bag of pixie dust. And if you do know someone who is good, they are booking jobs in 2024.

Click to expand...

Truer words were never written. My wife says, "why don't you just write a check?" and I reply, "that's just the beginning of the problems".

On the assembly lube thing, yes, but also come up with a way to get oil pressure before you start the engine. You probably can't turn the oil pump as you can on some automobile engines. I'd leave the injectors out and crank the engine until I saw oil pressure before starting. I have learned this lesson the hard way. Some engines are pretty tolerant of "dry starts", some are very intolerant. On a rebuilt engine the pump is dry, the filter dry, the oil galleries dry.

I'd not be as concerned doing the valve seats as you did. Lapping the surface is a good last step, even if they were freshly cut by machine. Cutting them at a different angle than the valve is done to let them beat themselves into a good seal, ie., to save the labor of lapping them.

KnotYet said:

C&M Auto Machine shop up the road in Alexandria is one of those old-school
shops run by a couple of older guys that might be what you describe above.

Click to expand...

Thanks. It's too late for this engine because it's now in pieces 500 miles from Virginia, but I'm considering "refreshing" the head on the second engine and will talk to those guys about it - they are just 30 min from my boat.

KnotYet said:

More notes: because you have had the crank reground, measuring its fit in
the new bearings is a subtle but important step. Do some reading
I have one word for you: Plastigage! OK, two more words: Assembly lube!

Click to expand...

Already done. I plastigaged (is this a word?) every main bearing, and all are between 0.051 and 0.076 mm (specs are 0.036~0.093 mm)
Assembly lube and 10x magnifying goggles to check for surface contamination on the bearing surface (How many machine shops do you think would bother with this?)
I'll post an update with photos later.

DDW said:

I'd leave the injectors out and crank the engine until I saw oil pressure before starting.

Click to expand...

Thanks. I was going to check the compression in each cylinder before starting for the first time, so this will serve as a pre-lubrication of the engine. I also got the oil pressure test kit so maybe it's a good idea not to start the engine until I see some oil pressure built in.

DDW said:

I'd not be as concerned doing the valve seats as you did. Lapping the surface is a good last step, even if they were freshly cut by machine. Cutting them at a different angle than the valve is done to let them beat themselves into a good seal, ie., to save the labor of lapping them.

Click to expand...

Thank you. It's one less thing to worry about.

Cooling nozzles, tappets, and main bearings are installed:




* I put a light coat of ATF oil on the back side of the main bearing facing the block and on each journal hole of the block.
Many Youtube mechanics urge about putting oil on the underside of the bearing because it will allegedly cause the bearing to spin later... one of them smartly says: "unless the manufacturer manual says overwise".

The Yanmar service manual says to put the oil there and there is a good Youtube video explaining why putting the light oil behind the bearing will actually help both parts to get seated properly and prevent spinning the bearing.

Thrust bearings are installed with the assembly lube:




* It was unclear to me which way to face the thrust bearing grooves because all Yanmar diagrams show the oil grooves on both sides facing away from the flywheel. On one bearing, the groves are shown facing the shaft and on another, they are shown facing the block - this is not correct.
Grooves on all thrust bearings must be facing outside (the crankshaft).
There is a short note in the manual about that (which I missed at first) and I found a reference to CAT thrust bearings where the block side is clearly marked, and it's opposite side from the oil grooves. This also makes sense because the grooves are there to get the oil between the bearing surface and the moving part (the crankshaft).

The crankshaft is lowered:




The main bearing caps are installed:




Bearing cap bolts are torqued to 24 kgf-m, which is 173 ft-lb or 235 Nm
I had to borrow a bigger torque wrench because mine was able to go only to 150 ft-lb.

If you are buying a torque wrench for that, get a 1/2in torque wrench going to 250 ft-lb - you will also need it for the head bolts.

I installed the bearings caps twice - the first time without an assembly lube but with green Plastigage strip under every cap. Just be careful not to rotate the shaft - it will screw up the measurements.
All my clearances were between 0.051 and 0.076 mm (specs are 0.036~0.093 mm) so I'm a happy camper.

I used a 10x Head Magnifier to check each bearing surface for foreign particles before lowering the crank and before installing each cap.

From what I could find, contaminations under the bearing surfaces and inside the oil passages are responsible for over 80% of rebuild failures.
so, lots of compressed air in every oil passage in the block and crankshaft, a liberal amount of brake cleaner, and lint-free cloth instead of paper towels.

I did not have time yet to measure the side clearance of the crankshaft, which should be between 0.132 and 0.223 mm
I will do this on the next playdate with this engine

Crankshaft rotates very smoothly - such a nice "buttery" feeling.

This is a long-overdue update as of 02/20/2023:

Pistons are in; idle gear is installed; oil pump, oil pan spacer, and oil pan are installed, sealed, and painted for protection.

Some lessons learned:

- Liners are all the same part number but can be marked in different "sizes": L, M, and S

- Pistons have the same part number but can be marked in 4 different sizes: ML, MS, L, and S

- You have to match pistons to liners according to the service manual. I got lucky to have liners and pistons sizes that matched. If not, I would have to try getting different liners or pistons.
The problem is there is no way to say which size they are until you open the part because they have the same part number on the package.

- Another important thing is to have proper torque wrenches. At least 2: a large one for high torque bolts like bearing caps and head bolts and another smaller 3/8 wrench for low torque bolts. Most are M8 going into aluminum, and the maximum torque is 20 Nm. You do not want under-torque bolts because they can get loose, and over-torque will cause costly damage to the expensive aluminum part.

I had to take a long break due to travel, but yesterday (03/12/2023) was a productive day.

A high-pressure fuel pump was installed, head valves were assembled, and the head was installed and torqued to specs.

Lessons learned:

1) Before you remove the high-pressure fuel pump, note the location of the mark. The service manual "conveniently" mentions this in the assembly section when it's too late.



I found one original engine photo which had the mark shown.

2) Installing the timer gear is a pain. Took me an hour or so. Two small cubes have to match with the pins on the pump while you are inserting the timer gear to mate with the idle gear at the specific mark, and it goes in with slight rotation because the gears are not straight.

At first, I put the cubes on the pins first and tried to align them with the slots while inserting the gear - this was hopeless because the cubes go inside the slots on an angle and there is no any play; plus, the timer gear has to rotate while mating with the idle gear.

I managed to do this by putting the cubes in the slots first a bit higher than the pins, and wiggling them into the pins while pushing and slightly rotating the timer gear.



3) Block and head surfaces have to be cleaned for the head gasket - no oil or sealant is needed.



4) Head bolts must be oiled but not drip oil because too much oil can fill the space under the bolt and hydrolock when you torque the bolt, causing damage to the block or incorrect torque. I put each bolt into the jar of oil and whipped the excess with a rug before installing them in.

The manual explains the torque procedure in 3 steps using the specific pattern to follow. To make it easier, I marked every bolt on the head with its "sorting" position using a paint pen. This way, it's much easier to follow the pattern.

Because of the low hours on the engine, I think the original bolts could be re-used as they did not stretch much, but I used all new bolts.

5) If you have a setup like mine with the engine stang and engine crane rolling on the floor, there is no easy way to get the head on top of the engine because crane's legs interfere with the stand's legs.

The best way I found is a "reverse cowgirl" position, shown below.





At this arm extension, my 2 Ton crane can handle only 0.5 Ton, so it's time to move this engine onto its wooden cradle, or it will be too heavy and unsafe to handle with the crane.

The next step will be doing the cylinders leak-down tests, finishing the head, installing the flywheel and gearbox, putting all the hoses and tubes back, and installing extra units.

"1) Before you remove the high-pressure fuel pump, note the location of the mark. The service manual "conveniently" mentions this in the assembly section when it's too late."

Great lesson-learned to read the entire manual start to finish before getting started. Thanks

Cost to have your engine rebuilt by a shop

By the way, if you are deciding to do a rebuild yourself or to have a shop rebuild your engine, check the video from the guys who had a similar engine rebuilt recently:


.. guess how much the invoice was before you watched the video...

for this kind of money, I would try to find a rebuilt or low-hours used engine from some military surplus to buy outright. It would be hard to find, but, man ...

Greetings,
Mr. W. Holy crapola! That's nice!