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Naiad pump leaking into 12V71 block

Discussion in 'Technical Discussion' started by Tom H, Aug 30, 2011.

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  1. Tom H

    Tom H New Member

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    I'm loosing oil slowly out of my Naiad system when not in use and when I checked the oil level on the Starboard engine it does appear higher. Is it possible that the pump may have an end seal leak that would bleed back into the engine? It's mounted above the gearbox next to the raw water pump. I had recently blown the pressure line out of the Naiad pump which when replaced and the oil refilled worked perfectly.
    This is in a 1979 Broward. Any help appreciated.
  2. K1W1

    K1W1 Senior Member

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    Hi,

    Get the engine oil sampled and analysed, if there is Hydraulic Oil in your engine it will show up straight away often as a high copper reading.

    You could also take the pump off the back of the engine and leave it over a bucket with the hoses connected at the same height as it would normally be mounted, this will soon tell you if the oil is leaking or not.
  3. Tom H

    Tom H New Member

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    I suspect this is the leak

    Thanks for the reply. The oil used in the Naiad is 10W40 engine oil and to be honest the oil level definately looks like thats where it's gone, just hoping someone may have had the same problem to confirm it. If so not having a manual I'm looking for a guide to the disassembly and repair. With a lot of these things it's never as easy as you usually would expect it to be.
  4. K1W1

    K1W1 Senior Member

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    Hi,

    Are you saying you are using 10W40 as the oil in your Stabilizer System?
  5. C4ENG

    C4ENG Senior Member

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    The Niads call for a straight 40 weight oil if I remember correctly.

    A Trinity yacht out there had a PTO for a Quantum system on the gear box. The PTO seals leaked and the hydro oil found it's way in the gear box. Fortunately no damage occurred to the gear box and the situation was corrected.
  6. K1W1

    K1W1 Senior Member

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    Hi,

    A straight 40 wt motor oil ?
  7. Capt J

    Capt J Senior Member

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    The older NAIAD system that was on the 75' Hatteras used 10w-40. This is what NAIAD told me to use in it. The system would have been installed around 1989 +/-. On that boat the hydraulic pump for the system was mounted on the front of the engine and belt driven.

    As for Detroit Diesels, 12v71's will show a different oil on the dipstick if for example the angle of the boat changes 5 degrees. On that Hatteras it had an extension and if I scullied fuel fore and aft, (or filled/drained the 600 gallon water tank) the dipstick would show up to a 1/2" difference in oil level.

    I would check the actuaters for the fins and see if the seals are leaking there. If not remove the pump from the engine and set it in a bucket with the lines attached and see if it's leaking. I'm not familiar with the pump, and cannot tell you if it could leak into the engine.
  8. dennismc

    dennismc Senior Member

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    Niads

    WOW !!! that sounds way too wrong, on my Vospers the pump and oil are totally separate, the oil is 32 W hydraulic and the pump outputs at 2200 psi, why would someone integrate and engine oil reservoir with an external system, sure sounds suspicious to me.
  9. Capt J

    Capt J Senior Member

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    The oil goes through your pump, that is how it pumps the oil to 2200 psi. There is no resevoir on his pump, but the pump is mounted to the engine. It has an oil supply line going to the pump, and then a high pressure oil discharge line that the oil goes out of. He thinks that the oil is leaking through the shaft seals, and into the crankcase of the engine through the shaft seal of the pump.
  10. dennismc

    dennismc Senior Member

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    Niads

    Well, lets hope the high pressure side of his system never gets to the crankcase of his propulsion engine, DD's don't do well with real high pressure oil.

    Interesting that DD would allow that installation when they don't recommend using the engine water as a heating source for external equipment even when protected with a HEX.
  11. Capt J

    Capt J Senior Member

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    Part of that I believe is that Detroit Diesels don't do a very good job at maintaining proper operating temperature at under 1000 rpms, so taking part of the heat out of the coolant and using it for heating your freshwater, would even further contribute to the problem of not maintaining operating temperature. DD's are very similar to Cat 3208s and you can let most DD's idle in neutral at the dock all day if you'd like and the coolant temp will never reach the thermostat temperature.

    I know with gear driven raw water pumps, there usually is an opening or weep hole in the shaft area between the water pump and the gear driven pump that if a shaft seal fails the saltwater will leak externally and not into the crankcase. I am not sure if the gear driven high pressure oil pump for that Naiad might have used is the same way.

    As for the poster, I'd have your oil anazlyzed on that engine as well to make sure your higher than normal oil level isn't fuel leaking from a bad injector, because that can and will wash out cylinder liners and crankshaft/rod bearings.
  12. dennismc

    dennismc Senior Member

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    Niads

    I was informed by the Service Mgr at DD that they want to keep their systems confined to their engines, warranty is void if adding external heating lines etc.
  13. Capt J

    Capt J Senior Member

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    My comments about DD not maintaining temperature was strictly related to the old 71 and 92 series......I consider the newer ones MTU, since they've pretty much dropped the DD off of most everything branding wise.......

    The MTU's are pain to get things warrantied out, I could see the dealer not wanting to add anything to complicate that process. The dealer has to take pictures, send them to someone, get an ok, then get back to you to schedule the work, but I didn't have any problems getting things warrantied, just time.......
  14. corinthian99

    corinthian99 New Member

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    I think what K1W1 (and what I'm confused by) is getting at is that you're saying your hydraulic system is running on lube oil rather than hydraulic oil. Is that true? I'm not familiar with your system but it just sounds really weird.
  15. Capt Ralph

    Capt Ralph Senior Member

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    The old Niad systems used their own 10/40 or 40w oil. This oil drove the gyro and the fins. There is no other hydraulic fluid used here.
    This oil was cooled by sea water either from a 3/8 hose from the mains sea water pump, or its own electric pump similar to an A/C pump. This heat exchanger is built into the gyro/valve/reservoir unit. Check the H E for oil leaks here.
    The adaptor plate on the back of the 71 was usually supplied by DDA. It has a weep hole like the fuel pump, raw water pump and most other PTO devices.
    I don't believe the Niad oil is going into the main engine.

    I used to run an old Roamer with 12v71 and Niads. We used the same CF-2, 40w oil in the mains, gears (TD514) and the Niad. 20+ years later she’s still running.

    On that same roamer, we did have a heck of a time chasing a low oil problem. It was the cylinder leaking. Had to buy a whole new styled unit and kit from Niad.

    Stay in touch,
  16. K1W1

    K1W1 Senior Member

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    Hi,

    That is what I was getting at, I always understood that Engine oil was not used in Hydraulic Systems owing to its tendencies to foam a lot.
  17. Capt Ralph

    Capt Ralph Senior Member

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    In a closed system, API CF-2 does not foam. Remember, it 2 stroke rated.
    On top of that, Niad at the time required CH-2, now CH-4 for the old systems.
    Were not talking about allot of pressure here. I can not spec the numbers off my head now, but I guess not over 300 psi. That's not much in the big pictures of faster hydraulic systems of todays fast reaction stuff.
    ,
  18. oceaneer

    oceaneer Member

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    something seems wrong here.
    most pumps on engines have a 2 seals and a weephole.
    one seals separates the pumped fluid (keeps it in the pump), then there is a space with a weep hole then another seal to keep the engines lube oil in.

    Oceaneer
  19. Capt J

    Capt J Senior Member

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    No, the NAIAD system ran much higher than that....... I think 1200 psi on the high pressure side.


    To the poster, I would check your heat/exchanger for the fluid loss. It is quite possible it's blowing it out in the cooling water.
  20. Capt Ralph

    Capt Ralph Senior Member

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    Yep

    Pumps and PTO adaptors. Said differently, we are talking about the same thing.