Preventing Turbo Hot Side Rust Lockup

[Manateeman]

We’ve seen this on other diesels but our Yanmar 170 hp turbo seems to love not spinning. We have a new stainless elbow and it downturns to a water lift. Out of the water lift into a big gas water seperator designed just like gen sets.
We let the turbo cool off before shut down. It’s not running high rpm a lot.
We had both the inside and outside of the hot side done with Cera-Kote but that didn’t stop the rust at the very bottom of the hot side and rust fused the bottom two tip of the hot fan to the casting. Some soot but no heavy cake. Rust.
Seems one the turbo freezes up engine oil accumulates in the air pipe going to the cooler. Turbo oil lines look fine and so does the antifreeze lines.
Looks as if it’s just rust forming. Condensation alone can do this?
Is there anything that can stop this. Anything you could inject into the turbo?
It’s got to be the salt or water mist...correct? Spray in Marvel Mystery Oil just as we shut down? We really don’t wash the turbo cause the air fan looks clean. Our bad on that? Very low engine hours. Always perfect oil.
Help. There must be an answer.
The Flummoxed and Dumbfounded Manatee crew.

[skipperpete]

How long is the hose up to the siphon breaker? If it’s too long, the drainback can cause water to splash into the turbo at shutdown without back pressure to let it drain peacefully into the Aqualock. On the other hand, maybe too much back pressure will do the same thing, ie blow water vapour back into the stopped or slowing turbo.
Yes it’s a recurring theme for me and I’ve been keeping a photo rogues gallery of the ones I’ve repaired or condemned, mostly caused by lack of use combined with the high humidity in the Aqualock but a few have been caused by bad exhaust design or failed mixers.
I,m always curious how the salt spray or mist can remain in the hot turbo scroll...... but it’s always the cast iron housing that corrodes
and that’s relatively cool. Well at least not beyond jacket water temp if you do a good idle down.

[Manateeman]

There is no siphon breaker. We think after we shut the engine down and close off the seacock the only source of salt water mist is the water which remains in the water lift. We have a small drain but are thinking a larger valve and a pump so we could drain it down completely. The bottom of the water lift is about two feet below the injection elbow. Maybe as the turbo cools it’s sucking water vapor up into it and over time, the casting rust builds up.
Even if we drain the lift, it will still be wet.
Somehow we need to dry inside the hot side of the turbo or maybe just opening it to fresh air will help. We can’t move the injection point without a huge custom exhaust and I’m not sure that would solve the problem.
Mark

[chowdan]

Originally Posted by Manateeman

There is no siphon breaker. We think after we shut the engine down and close off the seacock the only source of salt water mist is the water which remains in the water lift. We have a small drain but are thinking a larger valve and a pump so we could drain it down completely. The bottom of the water lift is about two feet below the injection elbow. Maybe as the turbo cools it’s sucking water vapor up into it and over time, the casting rust builds up.

Even if we drain the lift, it will still be wet.

Somehow we need to dry inside the hot side of the turbo or maybe just opening it to fresh air will help. We can’t move the injection point without a huge custom exhaust and I’m not sure that would solve the problem.

Mark

I can't report on my exhaust yet until end of the season, but I had to move my injection port aft of the engine.

Yanmar 4jh2-ute - 100hp engine had a wet turbo that was seized due to water. That said ideally you want to get that water as far as possible away from your turbo.

I'm betting that the warm water as it cools is rising up to sit in your turbo. I noticed the paint on mine on the inside showing some odd signs of condensation rust weeps. I'm curious what it will look like when I pull the elbow for inspection come this winter. Turbos running fine(200+ hours since having the elbow built)

[skipperpete]

There seems to be a tendency for the corrosion to occur more readily after the initial event and I suspect that the acidic condensate gets into the cast iron, either in the pits created or in the pores ( if cast iron is porous) so maybe a couple of coats of phos acid will pacify the embedded corrosion. The repair is largely dependent on the circumstances and the extent of the corrosion and lockup but generally there are 3 paths to getting the engine running again.
1. Replace the turbo... for the well heeled owner and the safest path to choose.
2. Replace the exhaust scroll only. Ok if the lockup leaves the turbine wheel undamaged.
3. Take off the scroll and polish out the surface corrosion with a suite of die grinder buffs and flap discs. This opens up the turbo tip clearance and probably reduces the efficiency but the effect is not usually obvious.
It’s always option 3 where the corrosion re appears so part of the seasonal layup for 3 is to remove the hose from the mixer elbow and bag the turbo outlet with a “thirsty hippo” or other moisture absorber in the bottom of the bin bag. A section of silicone hump hose (purosil) makes the removal from the mixer less of an ordeal. The other benefit of the desiccant thing is that corrosion in the exhaust valves and the open cylinders is also mitigated.

[skipperpete]

And here’s a few pics. One is a Yanmar on a genset, the next is one of the two on a Detroit 8v71 and the third is damage on a Yanmar 4LH where the crew tried to turn the stuck turbo with the compressor wheel. [ATTACH]264313

[Manateeman]

Thank you for the posts. We have ordered a new turbo and might have the rusted one rebuilt by a pro shop.,
We’ve tried coating the casting. That failed. Maybe there is some way to remove the moisture every time you shut off.
Some way to fog it or dry it.

[skipperpete]

Sadly it’s just a fact of life with a wet exhaust, often made worse by poorly thought out or corroded mixers. The cost of the damage caused by wet exhausts across the yachting community must be quite high and I’d be interested to hear about other cruisers woes with locked turbos and rusted cylinders.

[Manateeman]

Maybe a solution. There might be a company in China that can cast in stainless.
More info to follow as soon as I know.

[Manateeman]

Both Yanmar and Mastry have little in the way of recommendations. Leaving the engine running before shut down just helps a bit but it’s the heat still there in the cast iron that will suck the salt water vapor up and back to the turbo.
Rather than a giant valve between the injection elbow and the water lift we are thinking about the following.
1. A smaller valve that would break the vacuum. We’d put it in the down pipe.
2. Tee off the boost plug in the intake manifold so we could putt a shot of Marvel Mystery Oil mist right as we are shutting off.
3. Weld a 1-1/2 “ tee to the side of the Down pipe with a valve. Shut down then blow air into the boost port to dry out the hot side of the turbo. Not at high velocity so the turbo won’t spin ..it’s got .no oil pressure. Small shot of MM Oil as well.
4. Same as above but low velocity computer fan blowing into the turbo sir inlet and exiting tee on downside pipe.
Comments ?
Thank you. Mark

[Kastaway]

Spraying anything in the compressor side will have to go through the combustion chamber to make it to the turbine. You would have to spray directly into the exhaust to get to the turbine.

[Sailmonkey]

Every time I’ve seen this type of turbo rusting, it’s the design of the mixing elbow that is the cause. Usually the seawater injection is too close to the turbo and the elbow too flat. Not always an easy fix.

[Manateeman]

First, the mixing elbow. We’ve replaced the Yanmar part with an identical injection elbow in stainless. There is little to be gained from any reconfiguration of their design. We’ve asked the DeAngelo Exhaust shop in Lauderdale if changing the position of the injection point would improve things. They looked at the layout and said no. The drop angle is not flat it’s about 40 degrees and the top of the water lift is 2’ lower. The water lift goes into a large water air seperator which is a scale up of the design found in lots of gen set installations.
Good grief we are not idiots. Neither are the guys at the DeAngelo shop.

[Manateeman]

We understand the path air takes if we inject anywhere in the intake post the aftercooled. What’s the worst thing that will occur. You get a little oil in the cylinder or the diesel chugs along for a few turns.
We’re not strong on this idea because it might not work at all but we threw it out there because it was actually from a Ford engineer. Some of the new diesel trucks are having similar problems with turbos.
The race car guys just go stainless.
My bet is the hot side will need to be a stainless casting and today we received a few questions from China.
Mark

[Sailmonkey]

Nobody said you were an idiot. Nor have you said anything up until now about DeAngelo.

The separator isn’t a player in this problem. This is the proximity of the waterlift coupled with the type of mixer. I’d bet dollars to donuts that a mixer with a riser prior to the injection point would cure this problem. Something with a 1’+ dry rise followed by a dry inverted “U” followed by the injection point facing down.

Either that, or run the engine more often and harder, or fog after every use as you’re exploring.