DIY rebuilding of diesel engine Yanmar 6LY

[twistedtree]

Pistons come with the rings but not the liners. Have to order lines separately.

Why would this be if you MUST always replace pistons and liners together? I'm not buying that it's a must, especially on such a low hours engine. If the clearances all meet spec, then shouldn't it be fine?



Are all the liners damaged, or just some of them?


No doubt that replacing everything is the safest thing to do, so I don't mean to discourage you if that's your preferred path. But also keep in mind that replacing everything is certainly the lowest risk for a hired mechanic who is spending your money on the parts, not his.... So of course they will lean that way.

 

[Waterant]

Are all the liners damaged, or just some of them?

I tried to hone the best and the worst of the liners. The worst is hopeless with a deep round area where the rings rusted to it and after a lot of honing to get the rest more or less smooth, it's out of specs now.

The worst liner before cleaning:

The worst liner after:

The best of them does not have big unevenness, which i can feel with a finger but is still not as smooth as I want it to be. removing the rust at the top, which is still there, will require more honing and will probably get that liner out of specs as well.

The best liner after cleaning

The unevenness is horizontal, not vertical. i think there is a chance the flexibility of the piston rings would still compensate for it and provide enough compression at low diesel's RPMs but the new liners are not that expensive so replacing all seems like a safer bet.

No doubt that replacing everything is the safest thing to do, so I don't mean to discourage you if that's your preferred path. But also keep in mind that replacing everything is certainly the lowest risk for a hired mechanic who is spending your money on the parts, not his.... So of course they will lean that way.

i guess lowering risks here is worth an extra 2k to me to get all the new pistons. but each situation is different. I'll go to another shop today to see what they will say.

 

[pacopico]

I hear you on buying a lot of new parts, but in the case you have here the rust is your enemy and all that pitting is really the driver of your costs.

As for all new pistons, these are relatively high-horsepower light duty diesel engines (hence cast aluminum pistons) and even if you run them conservatively there's a lot higher thermal loading on these parts than the old, N/A diesel or gas engines the youtubers you might see are playing with.

For reference, one of our boats at my day job just failed a main engine due to improper injection timing and the operator not stopping the engine "in time" - scoring on 10 of 12 cylinders, two pistons totally stuck (thrown rods) two with broken wrist pin bosses on the cast aluminum pistons, two more with stretched wrist pin bosses. All this on a 38L/1,000HP diesel. Very similar design and performance-per-displacement as what you have and it went wrong before they could notice. Piston/Ring/Liner fitup is critical!

I'm certain you'll have another shot at the caviar and champagne next year.

 

[Waterant]

in the case you have here the rust is your enemy and all that pitting is really the driver of your costs.

One thing that bothers me is that all that pitting was under a thick and hard layer of carbon - you can still see the black rings around all the pits.

The engine was not run after it got seized by the rust, so how does the rust damage gets covered by the hard carbon?

Also, the worst rust damage is in cylinder 4, but the worst pitting is on pistons 2 and 5. the rest of the pistons do not have any pitting or just small imperfections, which can probably be polished.
It's possible the pits are melted aluminum from too much fuel and not the rust damage. I will get my injectors tested for sure and maybe even test the high-pressure fuel pump.

I just came back from another rebuild shop. Classic-looking old-timer with at least 50 years of experience looked at my pistons and told me to replace the two with the pits and keep the other 4. He measured them and did not find any issues - they just need cleaning and polishing.
I left them with him to soda blast and will confirm again next week to see if his opinion change. this shop will also be polishing the crankshaft and camshaft.

so, there is a hope to reduce this major expense from 6 pistons to 2.

I'm certain you'll have another shot at the caviar and champagne next year.

if keeping 4 pistons will work out, I may even see a gram or two of black caviar this year

 

[Gdavid]

One thing that bothers me is that all that pitting was under a thick and hard layer of carbon - you can still see the black rings around all the pits.

The engine was not run after it got seized by the rust, so how does the rust damage gets covered by the hard carbon?

The water ingress was due to a poor exhaust configuration, the environment in which the boat was docked (stern to a large fetch) or most likely both. The cylinders probably incurred much smaller amounts of water and damaged the internals but drained past the piston rings prior to being started and thus avoided becoming hydro-locked and the boat was run after this. It could have occurred multiple times.

It seems on this final occasion, the boat sat exposed for a longer period of time and sufficient time for the rust to lock everything in place.

 

[Waterant]

The cylinders probably incurred much smaller amounts of water and damaged the internals but drained past the piston rings prior to being started and thus avoided becoming hydro-locked and the boat was run after this. It could have occurred multiple times.

It seems on this final occasion, the boat sat exposed for a longer period of time and sufficient time for the rust to lock everything in place.

It could be, but it does not explain why the worst pitting by far is on piston 5, which is almost the farthest from the turbo (water intrusion point).
and piston 1 is the cleanest with no pitting at all.
in case of smaller water intrusions happening on many occasions, I'd expect piston 1 to have the worst rust damage because it's the closest to the water entry point.

i thought it might be related to the final position of the pistons in the seized engine, but i do not see the correlation.

unless the pitting was caused by incorrect fuel pressure because piston 2 and 5 seems to be on the same stroke and those are the only pistons with severe pitting.

The final position of the pistons in the seized engine:

 

[Gdavid]

Good questions, beyond my ability to answer but it would be a good idea to scope the cylinders of the other engine once you are done putting this one together.

 

[KnotYet]

It could be, but it does not explain why the worst pitting by far is on piston 5, which is almost the farthest from the turbo (water intrusion point).
and piston 1 is the cleanest with no pitting at all.
in case of smaller water intrusions happening on many occasions, I'd expect piston 1 to have the worst rust damage because it's the closest to the water entry point.

i thought it might be related to the final position of the pistons in the seized engine, but i do not see the correlation.

unless the pitting was caused by incorrect fuel pressure because piston 2 and 5 seems to be on the same stroke and those are the only pistons with severe pitting.

The final position of the pistons in the seized engine:

Since we can be sure that the water ingress happened when the engine wasn't
running, what mattered is whether the exhaust valve remained open or not. Two did.
It would be good to regrind the valves and seats to make sure they start out fresh.

The tiny water molecules would have no problem penetrating the porous carbon and
attacking the metal underneath, just as they would inside the injector nozzles. There
would be trace amounts of corrosive compounds present from combustion byproducts.

 

[lipets]

Great story to follow

Question did the injectors come right out or did you need a tool?

I'm asking because I'm thinking about pulling mine to checked

 

[porman]

If it hasn't been mentioned before, on this engine the number one piston is next to the transmission and the number 6 piston is next to the pulleys and belts. For water intrusion to happen an exhaust valve must be open. Looking at the position of piston number 5 it looks like it was probably just on it's way up to expel the gases through the exhaust valve.

 

[KnotYet]

Great story to follow

Question did the injectors come right out or did you need a tool?

I'm asking because I'm thinking about pulling mine to checked

Depending on the engine you sometimes need a slide hammer style puller
that threads onto the fuel fitting on top of each injector body

 

[jleonard]

Question did the injectors come right out or did you need a tool?

Depending on the engine you sometimes need a slide hammer style puller
that threads onto the fuel fitting on top of each injector body

If you look at my post, #61, you can see the rudimentary home-made puller I used to get my VW injectors out.
I used the same one with a different size nut on the end to pull my Cummins injectors.

 

[lipets]

I don't have the room for a slide hammer?

 

[twistedtree]

I tried to hone the best and the worst of the liners. The worst is hopeless with a deep round area where the rings rusted to it and after a lot of honing to get the rest more or less smooth, it's out of specs now.

The worst liner before cleaning:

The worst liner after:

The best of them does not have big unevenness, which i can feel with a finger but is still not as smooth as I want it to be. removing the rust at the top, which is still there, will require more honing and will probably get that liner out of specs as well.

The best liner after cleaning

The unevenness is horizontal, not vertical. i think there is a chance the flexibility of the piston rings would still compensate for it and provide enough compression at low diesel's RPMs but the new liners are not that expensive so replacing all seems like a safer bet.



i guess lowering risks here is worth an extra 2k to me to get all the new pistons. but each situation is different. I'll go to another shop today to see what they will say.

Scrap them all if that last picture is the best liner. Those are all trash.

 

[RT Firefly]

Greetings,
Mr. W. Agreed. Scrap them all.

 

[MVDarlin]

You may want to gain some working room and weight reduction when returning the block to the boat by reassembly of the head in the boat after the block is installed. In my engine rebuild experience that was how it was done.

 

[Waterant]

Great story to follow
Question did the injectors come right out or did you need a tool?
I'm asking because I'm thinking about pulling mine to checked

I did not use a special tool, but they were tight and required some persuasion with the long-nose pliers.

Just label them, so they go back into the same cylinder they came from. I did the mistake of mixing them (i labeled them with a marker which came off after ultrasonic cleaning).

 

[Waterant]

Scrap them all if that last picture is the best liner. Those are all trash.

Right, i know. All liners are getting replaced with new ones. i tried to hone two just to see how that tool works and if existing liners can be cleaned up or not (they can not)
I'm trying to save the pistons - will see how they look after the soda blasting at the shop.

 

[Waterant]

You may want to gain some working room and weight reduction when returning the block to the boat by reassembly of the head in the boat after the block is installed. In my engine rebuild experience that was how it was done.

This is how we removed it. i have a plan in mind to get it back with the head because i want to start and test the engine before i put it into the boat.
As i know, removing the head again will require replacing the head gasket ($300) and the head bolts because they are the stretching type ($17 x26 = $442)
i can probably reuse both but I'm not supposed to so, I will try to get it in one piece without doing that.

 

[Waterant]

I measured injector shims today (which i mixed up) and 4 are the same at 0.25mm, one is 0.15mm, and another one 0.35mm and i do not know which goes into which injector.
so, 6 shim sets are added to the part order, and all injectors will go to the shop for testing and assembly. if the shop will say i need the new nozzles, I'll get them on the next order.

Do not be like this guy!
keep every little part pared and labeled, so everything goes back to the same place even if they all look the same:

 

[Mako]

As I read the posts and the prices for parts, I'm again blown away by the expenses for this Yanmar. Since everyone is always lamenting Volvo parts prices, would they be similar to what the OP is experiencing?

 

[LN-RTP]

As I read the posts and the prices for parts, I'm again blown away by the expenses for this Yanmar. Since everyone is always lamenting Volvo parts prices, would they be similar to what the OP is experiencing?

Yanmar parts are ridiculous expensive.
Until I realized my Yanmar 6LP-STE are similar to a Toyota diesel used in the Land Cruiser: Toyota parts are a lot cheaper, but are the same parts and the same quality.
(The cooling system is obviously different but still lots of Toyota parts for 1/3 price)

 

[Waterant]

Yanmar parts are ridiculous expensive.
Until I realized my Yanmar 6LP-STE are similar to a Toyota diesel used in the Land Cruiser: Toyota parts are a lot cheaper, but are the same parts and the same quality.
(The cooling system is obviously different but still lots of Toyota parts for 1/3 price)

That's new. So you have some cross-reference table or Toyota engine model which is compatible?
I know your engine is different from my 6LYA but maybe I'll find something similar.

 

[LN-RTP]

That's new. So you have some cross-reference table or Toyota engine model which is compatible?
I know your engine is different from my 6LYA but maybe I'll find something similar.

Sold the boat 2 months ago: Yes I had websites showing Toyota parts, then
used those part numbers to search on ebay and Google.
Typical examples would be the timing belt, $200 Yanmar, $50 Toyota, belt tensioner $280 Yanmar, $45 Toyota.
The problem was that the diesel Land Cruiser is not sold in the US, only gas.
Hence I had to get som parts from overseas, but there is also a Land Cruiser parts guy in the US that can get any part for the diesel.
Also had luck with the 6LP-STE water pump including manifold and drive from Sweden of all places for $200 less than the US Yanmar unit and shipping was only $25: It was the real deal with Yanmar packaging and labels, etc.
There is a company in Vancouver WA who makes SS exhaust parts for the 6LP, excellent quality and cheaper than the Yanmar cast iron parts:

https://hdimarine.net/product/gm-stainless-steel-mixing-elbow/

Maybe they have stuff for your engine too?

 

[av8r]

HDI Marine is located in Vancouver, WA, down by Portland.

 

[LN-RTP]

HDI Marine is located in Vancouver, WA, down by Portland.

Thx.
Updated

 

[Waterant]

.SS exhaust parts for the 6LP, excellent quality and cheaper than the Yanmar cast iron parts:

https://hdimarine.net/product/gm-stainless-steel-mixing-elbow/

Maybe they have stuff for your engine too?

Great, thanks. I'll check with them because I'm redesigning the exhaust path as well to prevent the same issue in the future.
Having the original exhaust raised just a few inches above the waterline in the muffler is the sure way to get the engine flooded again.

 

[LN-RTP]

Great, thanks. I'll check with them because I'm redesigning the exhaust path as well to prevent the same issue in the future.
Having the original exhaust raised just a few inches above the waterline in the muffler is the sure way to get the engine flooded again.

Great, hope they have something you can use.
Here is ebay seller I bought Yanmar water pumps from:

 

[DDW]

I have owned a few diesels, currently a Cummins, Volvo, Yanmar, and Ford. Despite the internet mythology about Volvo being way overpriced, the fact is that the parts for any of the engines are expensive, and not much different between brands. There is more difference between markets: for example Volvo parts are cheaper in Europe than North America, and any of the parts are cheaper if found in agriculture or industrial markets than marine. For example the IHI turbocharger used on my Volvo is about $3500 from Volvo marine, exact same part from IHI for a front end loader is $800.

 

[Juggerknot]

Can you elaborate what you mean by the rings must be fitted?

To fit rings correctly, you need to measure the bore and using a tool, gap the rings according to the specifications. it isn't rocket science but is a crucial step in a good performing engine.