Re: [Amel Yacht Owners] Re: 4JH4-HTE TURBO MALFUNCTION

David Pawley
 

What happens is there is often residual heat in the turbine end, and when the Engine has stopped without the Exhaust cooling down adequately, and no oil circulating to take heat away. The heat will migrate from turbine end to the bearings and raise the temperature of the oil, till the oil "cracks" leaving a tiny deposit, perhaps blocking oil passages. Would think your bearings are roller type. At minimum your bearings need to be replaced and a good clean out of the labyrinths and Turbine. I'd say subsequent damage may have been done, more so because combustion hasn't been clean so Exhaust temperatures have been elevated, possible distortion of shaft. But still worth a go. Considering the highly balanced sensitive components suggest you get specialist dismantling. But you could save a few dollars by taking off the engine yourself. Good luck.


On 23 June 2014 15:00, amelliahona <no_reply@...> wrote:
 

Alex:  All my turbo maintenance experience is on aircraft and may not completely translate to failure modes on marine turbochargers, but here goes.  


Turbochargers are extremely simple items.  They consist of a center section with bearings and oil lubrication channels with seals to prevent the oil from going to the turbine or compressor sides of the turbocharger.  A simple shaft passes thru the center section bearing and seals.  On one side of the center section is a turbine (the exhaust side) and on the other side is the compressor blades and the scroll.  Since these things can spin at 30,000 rpm, balance and tight tolerances are imperative.  That is their most common failure mode.

If you can't turn the compressor blades by hand there are several possibilities:
1. Oil can coke on the shaft and bearings in the center housing from high oil temps (a good reason to allow the engine to cool at low RPM prior to shutting down).
2. Damaged or worn bearings
3. Binding of the turbine or compressor blades on their housings from some foreign object damage or overheating resulting in blade creep in the turbine side. Stainless steel melts at 1650 degrees F and in aircraft it is very possible to exceed those temps.  We have TIT (turbine inlet temp gauges on most turbocharged aircraft to keep at least 100 degrees F away from that melting point).  I don't know if marine turbochargers reach those types of temps or not.
4.  Exhaust deposits along with perhaps salt reflux caking on the turbine side.  In any event, if you can't turn this unit then an overhaul is most likely in order.  Usually an aircraft turbocharger can be overhauled for about $1,000, not sure what a marine engine turbo overhaul goes for.

Best of luck, 

Gary Silver
s/v Liahona
Amel SM #335


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