4tnv98 questions about internals and head damage

[franka02809]

Mechanically I am not very well versed. This is my first time opening a motor but I am interested and driven to learn about what I am seeing. The reason I started on this journey of removing the head is that I was getting compression out the radiator expansion tank. It would blow the coolant out the tank. I could see what looked like the combining of oil and coolant. I had a head gasket test tool but that thing would also bubble up and overflow almost immediately after starting. So the machine could be cold but it would still blow bubbles like crazy. In looking this up the general consensus was that it had to be a head or gasket issue. The pictures I am posting here are of the piston walls and the head before cleaning in more detail so I can get some help identifying what the problem was. In addition just before all of this the machine was running to hot. I ended up replacing the sensors inside the coolant housing attached to the head. Sorry I do not know the names of things just yet so I may make some mistakes here as I learn. It may be hard to detect what I see in this image that shows the head and one of the cylinders with visible damage to the head itself (missing metal)

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This is the inside of the cylinders and I can make out numbers etched in the top of each one so I think someone has already been inside here.
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I am wondering if the cylinder walls seem normal to have a black ring at the top. I am wondering if the build up I see in the cylinders and pistons is normal for these. I am trying to make sure I identify the issue before I clean more and check the block is flat with a square. There is marks on the block I can see from what looks like someone trying to separate the head from the block with a screwdriver. Another thing I find odd is one of the push rods seems smaller than the others and does not have the same marking the others do (the yellow ring) Once removed it looks like its a bit rusty on the bottom like it may be from another motor. Its the one on the far right of this image View attachment 20251126_161040796_iOS.jpg

 

[bmaverick]

Looking at the head images, has this engine ever used starting fluid? It has some telling signs starting fluid has been used before. This is why the pitting is seen.

For diesel engines, never use starting fluid or ether fluid. This does extreme damage to the metals in the head and pistons in diesel engines.

Clean all of this up per the Service Manual. Then re-assemble with a new head gasket per the Service Manual.

YANMAR YANMAR 3TNV82A 3TNV84 3TNV84T 3TNV88 4TNV84 4TNV84T 4TNV88 4TNV94L 4TNV98 4TNV98T 4TNV106 4TNV106T SERVICE MANUAL 0BTNV0-U0000.pdf

Found on the YTOG for free.

 

[bmaverick]

All of the carbon soot build up relates to,

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How to keep the soot away and ways to prevent having the head warp and crack on these Yanmar engines.

- Do not let the engine idle below 1200rpms for longer than 10mins max at a time. And the time is with 20mins between.
- Do use 10W30 summer and 5W30 winter for engine oil. Do not use the heavy thicker 15W40 as it will hold the heat longer in the engine. Yanmar makes engines to JIS standards, not SAE. So the cooling oil passages are narrower in metric.
- Do keep the air intake filter clean. A clogged filter makes the engine work harder and heat builds up within the engine.
- Do keep the radiator and the screen clean.
- Do check the coolant. Do not use extended life coolants in these vintage machines.
- Do start the tractor slightly above idle.
- Do not race the engine from slow to fast and fast to slow.
- Do slow the engine speed down gradually, idle for 15 seconds then turn the engine off.
- When parking and doing the engine shut-off, be on level ground, take and place the gear in neutral and if equipped, the PowerShift in neutral.
- Diesel engines, especially the 2-clyliner types will cause a lurch-back on the last 2 piston firings. To prevent the energy going to the drivetrain, be in neutral.

Some of these tips are from Deere, some are in the Yanmar USA bulletins and some came from the Yanmar JP website before 2018.
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[bmaverick]

Here is a 2TNV90 head damaged and with a crack due to starting fluid.

I didn't see a crack in yours.

 

[mrmikey]

.....visible damage to the head itself (missing metal)

Probably cause by pre-ignition or more than likely as was said starting fluid. It's odd tho, usually it's the piston that'll melt.
Definitely a head gasket fail. You can see where the cylinders are connected and it looks as if the water jacket and oil passages are connected too. Got a pic of the head gasket?

I am wondering if the cylinder walls seem normal to have a black ring at the top.

Yup, totally normal. That's the distance from the top of the block, head surface, to the top of the first combustion ring on the piston. Basically it's as far as the combustion gasses get to before they hit the first ring.

Cylinders look good, it would have been better if there was a bit of cross hatch left but there's no gouges or marks. Purpose of the cross hatch is pretty much to hold oil to lube the rings as the piston moves up and down.

As for the head your best bet would be to get the head surfaced, I'd bet money you're going to find it needs it. That pitted cylinder may give you a problem as far as retaining the valve seats especially around that intake valve, it looks as if there's nothing left.

If you're thinking someone else has been in there, any chance the previous owner slapped a head gasket in it to get rid of it? Or even stuck another ahhhh...less than perfect head on it as it's odd there's no piston damage on that same cylinder.

 

[franka02809]

Thank you for all the replies. I don’t think fluid was used. This is in a Takeuchi tb175 excavator. I have never used fluid in it. Thanks for confirming the black rings. I think they slapped a head in because the head was all rusty and the rest of the motor is painted black still. I will get some images up of the gasket soon. I thought the damage could have been from coolant leaking into the cylinder but I don’t know much about this yet. I do not think I want to risk running this head because I think, like some said, it may cause valve seal issues. I don’t want to do this once never mind twice. Also wondering if it can mess up things because one cylinder has more volume than the rest. What do people recommend for cleaning and prepping the block for the new head? I need to do something in place because I am not pulling the motor.

 

[mrmikey]

I thought the damage could have been from coolant leaking into the cylinder but I don’t know much about this yet.

Unless it causes the cylinder to hydrolock (water fills up the cylinder and being uncompressable, causes damage when trying to turn it over) water leakage into a running engine cylinder will usually clean everything up as it turns to steam effectively steam cleaning everything. Mind you, it'll rust eventually.
It looks as if there's been plain water used in it instead of anti freeze...not a good practice.

Also wondering if it can mess up things because one cylinder has more volume than the rest.

If it was a high performance engine yes, a small one like that I wouldn't be overly concerned about it. Is it perfect, no.

What do people recommend for cleaning and prepping the block for the new head?

A gasket scraper is pretty much all you need for cleaning, get a good carbide edge one being careful to keep it flat and not to gouge the block.
Once you get it cleaned, get a good straightedge, set of feeler gauges and check for warped or wallowed deck. Not that common an occurrence but it does happen. . Make sure you clean all the threaded holes out and that there's no pulled threads and no liquid in the holes. If there is when you put the bolts in and tighten them up it's a good way to, in a best case scenario, throw the torque off, worst case you can crack the block as you're trying to compress the liquid.
Check the pushrods also for straigtness, piece of plate glass works or something you know is flat to roll them across.
Change the oil if you haven't already.
You should get a manual, it'll be a lifesaver in the long run. You're going to need it for your torque values.

 

[bmaverick]

Thank you for all the replies. I don’t think fluid was used. This is in a Takeuchi tb175 excavator. I have never used fluid in it. Thanks for confirming the black rings. I think they slapped a head in because the head was all rusty and the rest of the motor is painted black still. I will get some images up of the gasket soon. I thought the damage could have been from coolant leaking into the cylinder but I don’t know much about this yet. I do not think I want to risk running this head because I think, like some said, it may cause valve seal issues. I don’t want to do this once never mind twice. Also wondering if it can mess up things because one cylinder has more volume than the rest. What do people recommend for cleaning and prepping the block for the new head? I need to do something in place because I am not pulling the motor.

FYI, it's just a re-badge Yanmar excavator for Taeuchi.

 

[bmaverick]

Unless it causes the cylinder to hydrolock (water fills up the cylinder and being uncompressable, causes damage when trying to turn it over) water leakage into a running engine cylinder will usually clean everything up as it turns to steam effectively steam cleaning everything. Mind you, it'll rust eventually.
It looks as if there's been plain water used in it instead of anti freeze...not a good practice.

If it was a high performance engine yes, a small one like that I wouldn't be overly concerned about it. Is it perfect, no.

A gasket scraper is pretty much all you need for cleaning, get a good carbide edge one being careful to keep it flat and not to gouge the block.
Once you get it cleaned, get a good straightedge, set of feeler gauges and check for warped or wallowed deck. Not that common an occurrence but it does happen. . Make sure you clean all the threaded holes out and that there's no pulled threads and no liquid in the holes. If there is when you put the bolts in and tighten them up it's a good way to, in a best case scenario, throw the torque off, worst case you can crack the block as you're trying to compress the liquid.
Check the pushrods also for straigtness, piece of plate glass works or something you know is flat to roll them across.
Change the oil if you haven't already.
You should get a manual, it'll be a lifesaver in the long run. You're going to need it for your torque values.
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The Service Manual is on the YTOG for free. I posted that early on.

 

[bmaverick]

What do people recommend for cleaning and prepping the block for the new head? I need to do something in place because I am not pulling the motor.

For a good cleaning agent, SEAFOAM and clean shop towels work really good.

 

[dodge man]

Some head bolts are only supposed to be used once. I don’t if yours are or aren’t.

 

[bmaverick]

Some head bolts are only supposed to be used once. I don’t if yours are or aren’t.

On YANMAR engines like he has, they are use only ONCE, then replace.

 

[franka02809]

Interesting I thought they were not torque to yield bolts so they could be reused. Was that bad information? I did find the carbide scrapers on Amazon like in your image, I will get them. I do have the manuals because I did not want to make things worse. I find some people use a long flat sanding block with sandpaper on it. Think that’s a bad plan? I will check it with a straight edge, light, and feelers for sure. I should grab a piece of glass to check the push rods. Not sure I like the idea of one not being the same as the others. It’s the right one in this image.

 

[mrmikey]

I find some people use a long flat sanding block with sandpaper on it. Think that’s a bad plan?

Theories good as long as you get all the abrasive bits out of the engine once you're done. Another good thing too is a sharpening stone either a new one or one that's been flattened.
It's funny, if you watch some of those rebuilding videos from Pakistan they use actual building bricks as a surfacing tool. Saying that, these are the same crew that rebuild a Cat engine in the dirt using rebuilt bearings and cheater bars as torque wrenches.

Not sure I like the idea of one not being the same as the others. It’s the right one in this image.

As long as it's straight and the same length you're good.

On YANMAR engines like he has, they are use only ONCE, then replace.

Didn't know that, I learned something new. I always thought the same as Frank that if they weren't torque to yield they were reusable, wonder what their theory is behind that.

 

[dodge man]

I think the fear is the head bolts stretch.

I’m sure you probably know this but don’t use sandpaper. They make stuff for metal, usually gray in color.

 

[franka02809]

Think the carbide scraper, carb cleaner and shop rags will be enough? I don't care what it looks like as long as its flat, clean, etc. I am not using anything that's not long and flat, I see some people with circular sanding disks and that seems like a very bad idea to me. I can plug all the holes for oil with shop rags (the blue ones) and use a long flat sander or a stone from there if you think it will be worth it. If you think its worth it can you recommend any sand paper for the flat sander or a stone? I am thinking about this because I can see some marks from a screwdriver pry it looks like. I just want to make sure I get a good flat seal and do not do this more than once.

 

[mrmikey]

Think the carbide scraper, carb cleaner and shop rags will be enough?

Should be unless the old gasket has be glued on and even then the carbide scraper should do it.

I can plug all the holes for oil with shop rags

You've also got the water jacket holes as well as the cylinder.

I see some people with circular sanding disks and that seems like a very bad idea to me

The white ones are supposed to be better but you've still got to be careful, although the cast block rather than aluminum is a bit safer. Pay particular attention to the area between the cylinders where the gaskets been blown out. If the engines been run awhile with combustion gasses blowing back and fourth, it may have a path etched....key word may. I'd go with a stone but that's just my preference, something like this, this is just the first pic I came across:

Did you get another head?

 

[franka02809]

I cannot image a round disk would make me happy once the straight edge came out. I have a guy on marketplace with a good head, waiting on a shipping quote for that. If it does not pan out soon I will buy a reconditioned one online, they sell for 6-700. If you went with a stone what grit would you recommend on the block? I can see that stone has 1000 and 6000 so I was curious. When using a stone what should I wet the surface with? Was thinking wd40 but what the hell do I know, lol . I already drained the coolant because it likely has oil in it or combustion gas. If I plan to flush it with water, drain, then fill with new coolant should I still plug the coolant jacket holes? Thanks for all the help!

 

[dodge man]

I’d try and find a local shop that can do the head for you. They can check it for cracks, get the head flat, check the valves and springs etc.

 

[franka02809]

Sorry no can do I'm a DIY guy even if it take me much longer and cost me much more. The engine will be staying in the machine and it will stay where it is till its done. I do not want to pull the motor because the rad and hydraulics do not look like a fun removal, lol. I know it is always better to let a pro at it but I want to be able to fix this one and any other one in the future. I currently have around 5 tractors and tlbs, several trucks etc all diesel.