4JH2E teardown report- 8000 hours

[rslifkin]

Originally Posted by markxengineerin

Ok- so it should touch both the raw water and the heat exchanger metal?
The worst corrosion happening is actually in the coolant area, so that threw me off, not having done any research yet.

Yes, needs to be electrically connected to the housing and in contact with the raw water.



If you're getting corrosion in the coolant side, a zinc isn't your issue. That means either the coolant / water concentration is too low, something (like salt water) has contaminated the coolant, or the coolant has been run too long and needed to be changed more frequently (every few years is good, the corrosion inhibiters only last so long and you can get trace amounts of salt in there too over time).

[markxengineerin]

Maybe a dumb question, but, would a zinc on the coolant side not have any benefit?

[Statistical]

Originally Posted by markxengineerin

Maybe a dumb question, but, would a zinc on the coolant side not have any benefit?

Coolant doesn't usually make a good electrolyte. Pure water as a coolant would but that is why pure water isn't used instead mixed with some type of glycol based coolant. That coolant solution improves operating range but also greatly reduces the rate of corrosion. It is why your car doesn't need zincs. Hot water heater usually has a sacrificial anode as plain water can be problematic.

Would it hurt? Probably not however it probably wouldn't help. Regularly changing your coolant and ensuring you don't get raw water intrusion into the coolant side would make a much bigger difference.

We use zincs for raw water well because we can't control the electrolytic properties of it.

[markxengineerin]

Makes sense, thanks. I am not sure about the frequency of coolant change from previous owner, must have not been enough. Now you have me wondering about the fresh water heater..

[Statistical]

Originally Posted by markxengineerin

Makes sense, thanks. I am not sure about the frequency of coolant change from previous owner, must have not been enough. Now you have me wondering about the fresh water heater..

Or as the prior poster pointed out you could have had salt water intrusion into the coolant loop. If that happened then the electrolytic potential of the coolant loop would go way up. If that was combined with insufficient coolant changes it could be even more.

As for hot water heater they aren't technically zincs they are made from magnesium but they are the same thing a sacrificial anode so the heating coils don't get eaten up.

https://www.defender.com/category.js...path=-1|299255

They tend to last a very long time sometimes even longer than the hot water heater so most people don't even realize they are there.

[chrisr]

really interesting thread and fantastic report - thanks for posting

we have a pair of 4JH2TE with 7300hrs so particularly interested. we do oil change every 150hrs and both are running fine (blow a bit of steam if 3000rpm for long, but temp gauge does not get over middle)

we live aboard and engines used frequently and well loaded

question : do you see any special age related concerns relating specifically to the turbos ? (we're aware of potential problems with water getting into the turbos, mixing elbows etc)

cheers,

[markxengineerin]

I would guess that wear is proportional to the power being made and time, so, if you have a heavy boat and use the extra horsepower, likely would wear out quicker than a lighter boat and the non-turbo version of the engine. I have no experience with turbocharged marine engines but a lot of industrial generators are using them for thousands of hours without too many problems. The turbo would not concern me specifically- just monitor oil consumption and shake /look at the impeller now and then to check for damage or extra play compared the the specification. If oil consumption ever goes up, the turbo seals are a possibility along with the other usual items.

[chris95040]

Really neat writeup, thanks!

Curious if any folks have experience to say if parts like ring grooves, halfway through their wear range, are really at 'half life', or does wear typically accelerate as things start to have more room to wobble around? Im sure it depends on the part...

[DougR]

Interesting report.

Any wear on the cam lobes and tappets?

[markxengineerin]

None that I noticed visually, but i did not measure. That's something easy to do, I'll report back.

[markxengineerin]

Doug- no measurable wear on the cam lobes- tappets I never did check but they looked ok.

Finally nearing the end of this, I'm looking for advice on setting the fuel injection timing. The manual doesn't seem to have what I'm looking for, either wrong model or it looks like a procedure for setting the timing when the pump is on a bench tester. I'm guessing that the engine is rotated slowly by hand, while one person observes a pulse of fuel coming out of the pump (hard lines removed) while another looks through the little hole for the flywheel mark, probably with a mirror setup? Is this for cylinder 1, which Yanmar says is the one closest to flywheel?

[markxengineerin]

https://www.cruisersforum.com/forums...ml#post3254915

This thread is the best reference to a procedure I can find, so I'm going to try it.

Other engines seem to require the "delivery valve" for cylinder 1 to be removed, and then fuel is expected to be delivered continuously as engine is rotating by hand until suddenly it stops- this is the point of injection and the point at which to check the flywheel mark. I am not sure both methods would produce the same result- anyone know?

Still other engines use a dial indicator on a reciprocating component in the fuel pump, which seems more precise, but I haven't seen anything like that for any version of this one.

[skipperpete]

Originally Posted by markxengineerin

https://www.cruisersforum.com/forums...ml#post3254915

This thread is the best reference to a procedure I can find, so I'm going to try it.

Other engines seem to require the "delivery valve" for cylinder 1 to be removed, and then fuel is expected to be delivered continuously as engine is rotating by hand until suddenly it stops- this is the point of injection and the point at which to check the flywheel mark. I am not sure both methods would produce the same result- anyone know?

Still other engines use a dial indicator on a reciprocating component in the fuel pump, which seems more precise, but I haven't seen anything like that for any version of this one.

I only use the “delivery valve removal” method. Slowly rotate the engine in direction of rotation until the correct timing mark is in the window..... if you miss it , go back about ½ a turn and try again. then , with the delivery valve out ....operate the priming pump and observe the fuel flow from the delivery valve holder. Loosen the injector pump securing nut and physically turn the pump until the priming flow stops. This is called spill cutoff and is the actual moment injection occurs. ( loosen or remove the 3 other injector pipes).
Tighten the pump up THEN check the accuracy by turning the engine back away from the flywheel pointer and watch for spill cutoff as you then turn the engine back toward the marks.
Some engines have NO timing marks so a piston height or a 360° protractor is used to find crank position.
Also some engines have auto advance so this needs to be considered too.
Yes a dial indicator is used on some types of pump.

[markxengineerin]

Hi Pete, I just spent a couple hours playing with it, then read your message. I used the other method, and after a lot of playing around developed a way that was at least repeatable, if not perfectly accurate (non delivery valve removal method). I used a rag to wick the diesel away from the delivery valve holder until it was at the very bottom of the countersink shape, so I was able to see with a flashlight when the level increased very slightly as I rotated the engine. Then was able to use a mirror to look at the mark on the flywheel, which luckily I had painted yellow during the rebuild. Flywheel was very rusty, I imagine on many of them it's impossible to see the marks at all. It was guess and check from there until it ended up just right.

I might compare to your method when I get a chance, just to see if I get the same timing, but I think what I did will pass for now, too many other projects to do before launching in November. Thanks for writing that up.

[skipperpete]

No worries, both methods work but the presence of the delivery valve makes the timing less accurate due to the unloader collar and a reliance on the spring tension.