New water pump overwhelming raw water system

Discussion in 'Downeast Engine Room' started by dnauhei, Sep 6, 2018.

  1. dnauhei

    dnauhei Senior Member

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    I have a belt driven impeller raw water pump. The bearing was shot and it was in poor shape so I had to replace it. The new pump is identical theoretically, but it seems to be pumping more water. All the hoses were leaking and the endplate for the heat exchanger are all leaking. I can tightened the hose clamps and that took care of most of it, but I can't get the heat exchanger endplate to stop leaking. The boats has only been run a few times in the last several months because a house repair project has stolen the summer from us.

    What's going on? Is it possible I have a clog in the raw water system building up the pressure? How do I find/get rid of it?
     
  2. c1steve

    c1steve Senior Member

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    The most pressure a raw water pump will produce is about 10 psi. I suspect that there may be a restriction somewhere, limiting flow. This could be in an oil cooler or the heat exchanger. I would take the caps of the heat exchanger, and look through the small tubes. There may be build up inside the tubes.

    You can clean with Rydlyme or Barnacle Buster, or some muriatic acid if you are careful.
     
  3. dnauhei

    dnauhei Senior Member

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    I'll give that a shot. Cleaned up the heat exchanger about a year ago, but maybe it is clogged again. I check the zinc and that is intact, so it's not the zinc corroding. But maybe it is something else.
     
  4. mike@mpi

    mike@mpi Senior Member

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    It's very possible it's a restriction causing your leaks. I've had a few customers that have leaks due to restrictions but no overheating issues. In the last case, a Cummins 450 C just last month the hoses to the aftercooler leaked and the engine ran at normal temperature all the way up to wide open. I put a pressure gauge in the pump outlet test port in the sherwood 1730 pump and revved the engine to 2000 rpm, showed 40 psi, and the hoses swelled alot. Cummins max allowed is 12 psi. Checked at top zinc on the aftercooler and had only 2 psi. Clogged aftercooler from marine growth. Normally its the trans cooler due to its small diameter. The fact that your heat exchanger is leaking now makes me think its after that, possibly your wet elbow or anything else after the exchanger . You can get a cheap gauge and some pipe fittings and start looking. These are some pressures I've found over the years. A sherwood pump can make almost 50 psi.fighting a clog. A serck aftercooler easily takes 100 without leaking , I test them at that, and a sendure cylindrical heat ex blows out the end seals at 25. And I stay away from acid, It destroys cast aluminum cooler housings. Just clean them mechanically.
     
    Last edited: Sep 6, 2018
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  5. mike@mpi

    mike@mpi Senior Member

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    Start at or as close to the pump outlet side as you can. If the pressure is low you know the system is clear and you need hoses, clamps and endcap seals. If the pressure is high keep moving along the flow path until it drops and then you've found your problem. A gauge and results is much better than just guessing.
     
    Last edited: Sep 6, 2018
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  6. Captinlon

    Captinlon Member

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    Just went threw a very similar situation with my 265 deere. I didn't have any leaks but had coolant issues. Found my gear cooler and my hydraulic cooler partially blocked off by old pieces of broken off zincs and marine growth. I played leap frog so to speak with a pressure gauge. Buy after seeing that, I went threw whole system. cleaned and flushed as the boat is new to me this season and have no clue when it was last done. Good luck to you
     
  7. dnauhei

    dnauhei Senior Member

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    I have heard "flush" and "don't flush because it can hurt stuff."

    What did you use to flush?
     
  8. Captinlon

    Captinlon Member

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    I drained old antifreeze, pulled and cleaned engine heat exchanger and aftercooler. Be carefully as to what you use on these. Some can handle different chemicals and some can't. Mine are copper and being a plumbing I used a product we use at work to clean coils and rinsed well with fresh water. Pulled all hoses and inspected. Flushed system with fresh water till it ran clear, replaced both thermostats and replaced impella on raw water pump. Replaced all zincs Replaced serpentine belt. Replaced engine coolant with new. Removed gear and hydraulic cooler, cleaned and changed zincs. Changed oil, learned hard way oil change pump, pumps faster that one would think. Pay attention, lol. It was a long weekend and well boat run 15 degrees cooler now.
     
  9. mike@mpi

    mike@mpi Senior Member

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    I haven't flushed the sea water side of any engine closed circuit cooling system in almost 40 years. I've heard people have good results with Barnacle Buster and Rydlyme. I remove whatever I think needs repair and if it can come apart, disassemble it, clean and reseal it. Things like heat exchangers and aftercoolers need to be inspected and resealed periodically. End zincs sometimes break off, bounce around in the water stream and then peen the water tubes closed. Aftercooler O-rings leak over time corroding the housings and then can put seawater into the engine intake air stream. The charge air side of the aftercoolers clog with oil residue from the CCV's and the cores should be cleaned by a radiator shop and then the assembled unit needs to be pressure tested. None of this gets done by running a cleaning flush. These parts are simple to take apart and live a tough life.
     
  10. BillD

    BillD Captain

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    I did some background checking on your Chrysler Nissan SD33.
    If I'm not mistaken the engine is 30+ yrs old ? Lots of marine age.

    When was the last time you took apart and cleaned the "entire" salt water cooling circuit including checking the mixing elbow.

    I'd follow Mike's lead. If the cap on the heat exchanger (HE) is leaking due to high pressure...the blockage must be distal to the HE. (mixing elbow could be partially blocked due to corrosion)
    30 yrs of marine age...plenty of small passages to get blocked over time with hard deposits, slime you name it.
    Regards, Bill D
     
  11. dnauhei

    dnauhei Senior Member

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    Yes, this all makes perfect sense now. I can see my fall project is going to be going through the saltwater cooling circuit piece by piece and cleaning every out. Thank you, Bill and Mike!
     

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