My Yanmar 4JH3-te needs a rebuild?

[jrobert890]

Hi Folks, I'll start by apologizing for the long post.

I'm sure everyone is looking forward to the holidays and the long cold winter . I just bought a new boat (new for me anyway) in July and on my 2 day trip home after she was launched I had to add about a quart of oil every 6 hours. I know I will take a lot of heat for this, and I should, but I didn't have a diesel mechanic look at the engine during the survey. I am trusting and a bit naive sometimes. The engine starts right up and runs well. There is a little smoke while running, but not alot, at least I don't think so. I was advised by a few mechanics that it could be stuck rings from sitting for 1.5 years, or fuel lift pump diaphram failure or turbo seal. I was worried, but I still had hope. I took a few trips in the summer and hoped the engine would improve. I'm still topping up the engine with 1 qt/6 hrs. Well before haul out last week, the yard finally did a diagnostic. The yard said that engine doesn't have a fuel lift pump diaphram, so that is out. The mechanic did a compression test and it was 400 psi across all 4 cylinders. He added oil to the cylinders and compression came up to 420 on one, 470 and 480 on others. I'm don't know what the compression spec is for this engine, but if someone knows and could share, that would be great. The injectors all looked clean, no carbon or discoloration. They still want to look at the turbo. I am now thinking worst case and thinking bad rings, worn cylinders. I bought the boat at a good price, but I didn't steal it and it was a stretch for me. I am thinking that I now need a rebuild, rebuilt short block or something along these lines. I don't want to repower with a new engine, since I don't want that bill, or have to mess with stringers and shaft angles, etc. I think I'm still looking at a $15 - $20K bill....ugh. Anyway, any thoughts? What would you do, if you were me? Btw, the previous owner, by way of the broker said he didn't have an oil consumption problem...hmm. I'm thinking of asking them (broker/previous owner), if they want to do the right thing and split the cost, if it turns out that I need a rebuild. Again, thoughts.

I hope everyone is enjoying the holiday and have a Merry Christmas!

[TreblePlink]

With your initial compression test showing 400 for all cylinders - that sounds like they're OK. I would do the oil in the heads test again to see how repeatable those numbers are AFTER you get some more time on it - maybe the rings just need to re-seat again after prolonged storage.

Added: Are you using full synthetic oil? Sometimes oil consumption or leaks increase with it...

[Jammer]

I am not going to claim I am an expert but I offer these insights.

The first Fact to Consider is that even at a quart every six hours you could, depending on your goals for the boat, just live with the amount of oil it consumes, at least for a while. The compression test shows that there is significant bottom end wear but perhaps not so much that the engine is not usable.

Oil consumption problems are cumulative. Again depending on the goals you have for the boat you could consider just doing the valves and calling that good enough. It would not be unusual for the valves to be at least half of the problem. Likewise a good deal of the problem could be the turbo, maybe if you take care of the turbo and the valves you can get another 1000 hours out of the engine, say, and that might be all you need.

I would be inclined to replace the entire engine rather than replace the short block. If the block is failing due to wear it would be surprising to find that the other components are in good shape. Here's a guy who has a rebuilt 4JH2 in Florida for $7,000. Might be a better deal than fiddling with what you have. I just found it in a web search, I don't know anything about the seller:

Yanmar 4JH2-HTE Diesel Engine - DieselEngineMotor.Com

[jt11791]

That's a lot of oil loss. If you are burning it, the exhaust should be quite smokey (blue). Are you sure it's not a leak?

400psi even across all cylinders is good. IF it is burning the oil, maybe a bad valve stem seal (or two)? Might only need a top end rebuild.

How many hours on it?

[Wotname]

I think you are a long way away from considering a replacement at this time. Keep looking at the simpler things first.

All good suggestions above (valves, turbo etc).

In addition, try using the engine hard for some hours (say 10+); by hard I mean running at near max continuous RPM with an occasional burst of WOT. Running at idle or very low rpm can cause bore glazing and increased oil consumption; hard running can sometimes remove it.

[Hobie_ind]

Originally Posted by Wotname

I think you are a long way away from considering a replacement at this time. Keep looking at the simpler things first.

All good suggestions above (valves, turbo etc).

In addition, try using the engine hard for some hours (say 10+); by hard I mean running at near max continuous RPM with an occasional burst of WOT. Running at idle or very low rpm can cause bore glazing and increased oil consumption; hard running can sometimes remove it.

I'd agree.. you're a long way from deciding on replacement yet. As others have already suggested, a good mechanic would confirm a number of things before suggesting replacement. ie.
- Exhaust smoke / colour if any?
- When you remove the oil fill cap on the tappet cover, while running are you seeing a lot of venting? Are you seeing lots of oil in the breather where the crankcase vent runs to?
- Is it a clean engine bay with clean absorbent pads underneath so that you can see whether there's any leaks?
- Oil pressure?
- Abnormal metal in the oil filter? Oil analysis indicating extreme deterioration/contamination of any kind?

My 4JH3-HTE wasn't using as much as yours when I got it, but I did notice a reduction in consumption and my exhaust was cleaner after I ran it hard for an extended period which leads me to believe there was some glazing. As suggested above, you may have the same. I also tended to notice that mine seemed to drop about 1/2 quart on the stick and then 'stabilize' there. Are you 'topping' up with 1/4 or 1/2 quarts at a time, or when it gets to the bottom of the xxxx hatching on the dipstick? Might be worth some experimentation before jumping to expensive conclusions. Especially if the engine is still running well other than oil consumption. I've got an airplane that if you put more than 5.5 quarts in (it's designed for 6), you might as well dump the extra on the ground. It blows anything over 5.5 out within a 1/2 hr. Completely different design I know, but still worth checking before ordering a new engine.

Another friend with a 4JH3-HTE had a Yanmar rep in Australia convince him he needed to replace his engine when he bought his boat. Another mechanic had a short list of questions for him: Does it start right away every time you hit the starter? Excessive smoke? Runs smooth? Able to make full rpm with the correct prop on the boat? Coolant clean and stable? Oil pressure good? His answers were Yes, No, Yes, Yes, Yes, Yes ..... The second mechanic suggested he just adjust the tappets, rebuild the injectors, clean the fuel tanks, and head out on his circumnavigation. 4 years later he rolled back into Australia with the same engine, 1200 hrs more on the Hobbs, and virtually no issues in the interim.

No guarantee yours is the same, but I think you're too early to be writing cheques for a new engine.

Good luck.

PS> Again, its a completely different engine, and I can't find Yanmars recommendations anywhere, but it can be surprising what 'allowable' oil consumption is for some engines. My Lycoming is over 0.5 qt / hour as long as the oil pressure is within limits. That's for a certified aircraft engine!

[Hobie_ind]

Originally Posted by jt11791

That's a lot of oil loss. If you are burning it, the exhaust should be quite smokey (blue). Are you sure it's not a leak?

400psi even across all cylinders is good. IF it is burning the oil, maybe a bad valve stem seal (or two)? Might only need a top end rebuild.

How many hours on it?

I forgot to add. I also looked for compression specs for my 4JH3-HTE and couldn't find them anywhere from Yanmar. That they're all even though to me is a good sign and in the absence of excessive blowby, I'd also be less likely to expect broken rings or a bad valve/guide as all cylinders are pretty even.

I did find this on another thread though:

The engine is a Yanmar 4JH2-TE 1993 vintage. The surveyor did a simple test and determined there was excessive blow by. His findings started my inquiry. Manufacture specs for compression for this engine are 412psi with a lower limit of 341."

Again, different model....

[jrobert890]

Wow, some good replies, thank you everyone, where do I start:

So picked up the boat at the end of July with 2900 hours on engine. I added another 120 before she was hauled this week. I didn't baby her and ran WOT occassionally, but it would begin to overheat after a few 2 - 3 mins, so I would back off. I wanted to run Barnacle Buster through engine, but didn't find an opportunity to do that.

- standard oil in the engine, not synthetic. Rotella 15w 40
- I'd like to get full use out of the engine. NJ to Florida, Bahamas, further South at some point
- no excessive oil in engine bay, but some, but that is from breather hose going to turbo. there is some puffing out of the oil filler hole. Did not do an oil analysis
- some light blue smoke, but not alot
- worn valve guides is usually indicated by puff of smoke on startup, I don't have that, just steady light blue smoke as she runs, but not too heavy

[Wotname]

Originally Posted by jrobert890

Wow, some good replies, thank you everyone, where do I start:

So picked up the boat at the end of July with 2900 hours on engine. I added another 120 before she was hauled this week. I didn't baby her and ran WOT occassionally, but it would begin to overheat after a few 2 - 3 mins, so I would back off. I wanted to run Barnacle Buster through engine, but didn't find an opportunity to do that.

- standard oil in the engine, not synthetic. Rotella 15w 40
- I'd like to get full use out of the engine. NJ to Florida, Bahamas, further South at some point
- no excessive oil in engine bay, but some, but that is from breather hose going to turbo. there is some puffing out of the oil filler hole. Did not do an oil analysis
- some light blue smoke, but not alot
- worn valve guides is usually indicated by puff of smoke on startup, I don't have that, just steady light blue smoke as she runs, but not too heavy

IMO, this is where you oil is going - being burnt and then out the exhaust. There should be no blue smoke - as in none.

I have no experience with turbos but I would be getting it checked.

[geoleo]

Originally Posted by Wotname

I think you are a long way away from considering a replacement at this time. Keep looking at the simpler things first.

All good suggestions above (valves, turbo etc).

In addition, try using the engine hard for some hours (say 10+); by hard I mean running at near max continuous RPM with an occasional burst of WOT. Running at idle or very low rpm can cause bore glazing and increased oil consumption; hard running can sometimes remove it.

I have had 2 of these 4JH3-TE engines in 2 sailboats . Never burned excess oil and oil even stayed somewhat clean. The above is great advice -- also 30weight oil diesel grade and run it above 2000 rpm to keep it cleaned out. The Turbo is not your problem. Also put a pint of Marvels Mystery oil in the oil !

[Hobie_ind]

Originally Posted by jrobert890

I didn't baby her and ran WOT occassionally, but it would begin to overheat after a few 2 - 3 mins, so I would back off. I wanted to run Barnacle Buster through engine, but didn't find an opportunity to do that.

If the previous owner was having overheating issues, it probably hasn't been run hard for a while. Coupled with sitting for an extended period..... you need to figure out what's happening with the cooling, then run if hard for a bit to see if glazing might have been the issue.

I'm assuming you've checked the raw water impeller, intake hoses for blockage already? After two years (?) of sitting, the impeller may have set or even hardened and be missing blades now after running a bit.

Regards,
Mark

[Rick Williams]

I have a 4JH without the turbo and found out after the survey and my purchase check cleared that the boat had "sunk" at the dock, the engine had partially filled with water and the PO had tried to start it. The engine ran well enough during the in-water tests and getting her home but the first time we did a compression test it was decided we needed to rebuild.
Taking the engine in and out and rebuilding ran about $8,500.

[oleman]

A quart of oil in 6 hours is NOT enough oil to cause a panic. More important does the engine start easily and run under load to the max RPM it is rated for. So she has a little smoke and blow-by MORE important is the oil pressure correct for the engine. You absolutely do not want a bearing failure at sea.
I would service the cooling system, overheating is BAD for any engine especially a well used diesel.
My rule is if the engine is reliable and produces enough power to get the work done run it until it is no longer reliable or useful then do the expensive repairs and only as required.

[kenbo]

Forget Barnacle Buster, it's very easy to pull the heat exchanger core out of that engine. It will give you the opportunity to check for galvanic corrosion on the heat exchanger end caps and renew the O-rings as well.

Also make sure that the correct thermostat is installed and that there isn't an air lock on the hoses to the hot water heater.

If you're pushing that much oil it would be wise to pull the mixing elbow and look for carbon build up on the dry side and corrosion/blockage on the water inlet.

[captlloyd]

Originally Posted by oleman

A quart of oil in 6 hours is NOT enough oil to cause a panic. More important does the engine start easily and run under load to the max RPM it is rated for. So she has a little smoke and blow-by MORE important is the oil pressure correct for the engine. You absolutely do not want a bearing failure at sea.
I would service the cooling system, overheating is BAD for any engine especially a well used diesel.
My rule is if the engine is reliable and produces enough power to get the work done run it until it is no longer reliable or useful then do the expensive repairs and only as required.

Agreed. And I would never let a marina do my engine work. Unless of course you don’t mind paying a lot extra.