Turbo diesel help

Hey everyone - I’m looking for some help. Or at least looking for someone to point me in the right direction. I’m trying to troubleshoot some turbo diesel problems. I’ve talked to a few people - none of who are mechanics - and it hasn’t helped. Clearly.

A diesel is a diesel right… Even it it’s in a boat. So I’ll take advice from anyone who has some mechanical background. This is a diesel from 1989 and has, to my knowledge, absolutely no electronic components. Everything is mechanical. It’s an 8 liter inline 6 intercooled turbo diesel like the type you would find in a semi-truck.

The clues:

  1. Most obvious synthem is blue smoke on start. Especially bad on cold start… but after 20-25 minutes of idling to temp it will smoke less but will definitely continue.

  2. Turbo compressor fan blades are covered in oil. Air filter had oil in it.

  3. Past 75% throttle you begin to see gray smoke out the exhaust.

  4. I’m unable to reach the 30mph rated speed of the vessel. I can approach 20mph at about 80% throttle but it doesn’t want to go beyond that. (for anyone inclined to ask - the bottom of the boat is completely clean as well as the running gear, props, etc) But I’m missing about 1/3rd of the engine output.

I suppose smoke could be from leaking valve guides. It’s also possible the cylinder walls or rings are shot. That’s a bit of an extreme conclusion… but possible. The engine hour meters only show about 400 hours of run time. I’d test compression if it wasn’t such a pain in the butt on diesels.

My primary suspect right now is the turbo. The turbo fan blades are covered in oil. So it could be that the seal isn’t holding and sending oil right in to the cylinders or in to the exhaust where it’s burning off as smoke. Or it could be that the oil isn’t draining out of the turbo properly and a plumbing issue… so even if I replace the $4000 turbo it will fail again?

Poking at the turbo…

  1. The compressor wheel has basically no play I can detect. Doesn’t wiggle at all.
  2. Seems to spin freely. Doesn’t make a noise when I turn it by hand. But… Feels a little heavy for a rotating assembly and will slow and stop fairly quickly.


  1. No oil in coolant.
  2. Engine starts pretty much instantly.
  3. Two identical engines. Port and starboard. Both have exactly the same problem.
  4. Engine doesn’t seem to have any issues revving up to full throttle in neutral. But… max RPM seem a little low at 2100 when max should be around 2500.
  5. I don’t have a boost gauge and would need to attach one… I’m not sure where, how, or what the normal boost pressure should read.

Any thoughts or ideas on things I should try or investigate? Anything else I should check for clues?

Is the compression test as painful as spending $4000 on a turbo to find out if it was piston rings all along?

If this engine has a crankcase recirculation system, that seems the only way the air filter to the turbo impepeller could be covered in oil. Check to see if there is tube or pipe between the 2. If there is, and I think there should be, I’d say the blowby from bad or stuck rings are flooding the intake with oil. That would explain the smoke and the power loss. A leaky turbo oil seal would not kill the power that much.

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Here’s a photo of the oily turbo compressor blades.

Check if the oil return line from the turbo is restricted.


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Yeah that’s what I’m looking for. There are so many different directions to go I’m getting dizzy :slight_smile: I’m told that it is very uncommon for diesels to have blowby. And given the number of hours on this motor (almost no use) I’ve put lower block issues low on my list. But that could be a bad assumption.

I did try a few simple things:

  1. With the engine running - I removed the oil dip stick and put my finger on the end of it to feel for a pulse of air. Nothing. There’s no “breathing” from the oil dipstick.
  2. With the engine running - I removed the oil cap and covered the filler hole with my palm to feel for a pulse or “breathing”. Nothing. Didn’t feel any pressure.

These quick tests logically came to mind. But I didn’t find anything.

It does have a hose that comes from the top of the crankcase and leads down to the turbo air filter. However, the hose terminates outside of the air filter. The hose does not lead directly in to the intake… it just vents gasses outside of the filter.

If the turbo isn’t properly developing rated boost levels… I’d expect to see the black smoke at 75% throttle. Does that add up or am I making a bad assumption?

This is probably a dumb question but… How do I test if the line is restricted? Simply blow in to it?

I don’t think a leaky turbo seal would affect its ability to spool up. A bad bearing, maybe. If, as tester suggested, the drain tube is clogged, the bearing won’t last too long.

Remove the oil return line from the turbo/oil pan/engine block and try blow compressed air thru it.


I’ll try that tomorrow thanks! It’s a 2hr round trip to check anything so… if there’s anything else I can try while I’m out there to report back here let me know.

Oil on the compressor blades of the turbo and smoke out the exhaust usually indicates a restricted oil return line from the turbo.


Ahhhh I forgot to mention one big mystery! I don’t know if I can trust my instruments here because it seems so absurd but… My oil pressure appears to be way too high… I’m reading around 70+ PSI at idle and higher at at higher rpm. Rev it up and oil pressure can go up to nearly 80. That’s the maximum the gauge can read out.

Both engines show this. 70 or 80 oil pressure. Never less.

When I first saw this… I shut everything down and changed the oil and filters. This engines hold an insane amount of oil and each engine has 2 gigantic oil filters. I put new oil in to spec on the manual… fired it up and…

Again. Had high oil pressure. No change. If there’s a restricted line… That could explain it…

Studying a schematic… Looks like when I fire the pressurized air in to the turbo oil return line tomorrow it will go straight in to the pan. Then probably back out though the dip stick.

8 liters sound a little small for a tractor trailer. The 6 cylinder Macks were 672 cubic inch, the Cummins were 855 or 902, don;t remember what the Cat was but I think if was bigger than the Mack. The GM or Detroits were smaller being a two stroke. The Detrots would turn a lot of RPM but the others would be really overrevving at 2500. The power in a diesel is controlled by the fuel pump and boost. It is possible to change the shims and springs in a pump to get better fuel mileag but it really kills the power.

I think you’re right. The book for the standard “industrial use” engine (only manual I have) says 8.821 liters (538.3 cu. in) with compression of 17:1 and a max 2,200rpm.

However, the rated output for the vessel is 2500 rpm for 30mph burning 37 gallons of diesel per hour in a magazine article that reviewed performance. It may be that the marine variant of the engine is modified for increased output? Or someone fudged a number. I know the marine variant of the engine has a lot of differences since some of the part numbers for it… don’t exist. My understanding is there were only 6 of these engines ever built.

The alternate power plant was twin Caterpillar 3208TA V8 Diesels. I’ve got the Hinos.

I was not familiar with Hino, it came to the US in 1995, the year I retired. Your engine is the largest that was made but did go above class 7 whicc includes tractor trailers but not really heavy duty models which are class 8. The Hino would be suitable for a city pickup and delivery tractor trailed or one limited to light loads. Check your fuel tanks for water, it reall plugs up those fuel filters. I liked the Wix fuel filters for my Mack, they had a drain valve on the bottom to drain water. Don’t empty the filter, a dry diesel is a bear to start.

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30 years old and only 400 hours (if that is correct,) is rough.
I don’t have any experience with Hino’s personally, but make sure the oil, oil filters, and fuel filters have been changed recently. with that much sitting, I would be concerned about sticking rings, but only after checking the oil lines as Tester suggested.

I had a turbo seal go bad on a brand new International mechanical engine once- to where the turbos started pushing oil into the intake, which the engine started running on the oil. They couldn’t shut the truck off, and it was bellowing TONS of smoke. Fire department showed up and cut the fuel lines- but the engine kept running until it ran out of oil. So I’d say don’t run it too long with a leaky oil seal if that is what it ends up being :slight_smile:

Might the valves need adjusting?

Is this a saltwater boat by chance? Have you kept up on your zinc replacement? If not, have you checked the props for corrosion?

Also check for a spun prop, which is when the rubber bushing between the propshaft and the blade breaks. (this can happen no matter what kind of water your boat is in)

Obviously, while you’re checking those things, make sure there isn’t anything wrapped around the prop, and make sure the prop blades aren’t damaged from smacking something.

He’s got twin engines, so I’d guess two props. It’d be odd for both props to have the same problem.

It’d be just as odd for both engines to have the same problem. :wink:

Plus, it only takes partially losing one prop to slow the thing down.