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Upper coolant hoses Collapsed

Discussion in 'Diesel Engines/Drives/Transmissions/Props' started by Joint Custody, Nov 20, 2020.

  1. Joint Custody

    Joint Custody Well-Known Member PLATINUM Sponsor

    489
    Sep 20, 2017
    Lake Powell Utah
    2001 460 Sundancer
    Twin Cummins 6CTA8
    Just wondering if this is normal both engines upper hoses are collapsed when boat not running.

    F996525C-A351-4E14-B728-0B33B4E77CF8.jpeg
     
  2. techmitch

    techmitch Well-Known Member GOLD Sponsor

    May 1, 2008
    Chesapeake Bay, Middle River/Frog Mortar Creek MD.
    1999 270 DA
    Twin 4.3s W/Alpa I Gen II's
    Does the system not have a coolant reservoir/over flow tank? Possibly bad caps.
     
  3. Irie308

    Irie308 Well-Known Member SILVER Sponsor

    May 28, 2013
    CT
    2004 420 Sedan Bridge, GHS Hydraulic Lift
    Dual Raymarine E120W
    AB Mares 10 VSX with 30 hp Tohatsu
    Cummins 450C 8.3 L Turbocharged
    mine does collapse which I've read is common however not sure if I've seen it by that much.
     
  4. my3sons

    my3sons Well-Known Member GOLD Sponsor

    Feb 24, 2009
    NY (Lake Erie)
    2004 400DB, Onan 9 kw Gen, Highfield RIB,
    Cummins 6CTA
    Judging by the looks of that hose, I'd agree with Mitch, but both pressure caps at the same time having the vacuum valve stick is a little weird. Sometimes an old soft hose will slightly collapse when the engine cools if there is a little air in the system, like right after I am messing around with the cooling system, cap off, draining and filling etc, as the air works it's way out, no more problem, but that one is really sucked in. When the engine cools, the contracting volume of coolant in the engine draws coolant from the overflow bottle, if the valve is stuck or clogged, it can't and it causes the vacuum that collapses the hose. Tap on the pressure cap with a screw driver handle or ? and see if the hose comes back. I'd replace the caps and if the hoses are old and just don't feel like there is much support in the walls as it should have, new hoses too. That hose looks old:)
     
  5. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    Is that not the reason some hoses come with a spring?
     
  6. my3sons

    my3sons Well-Known Member GOLD Sponsor

    Feb 24, 2009
    NY (Lake Erie)
    2004 400DB, Onan 9 kw Gen, Highfield RIB,
    Cummins 6CTA
    I haven’t seen anti collapse springs in years. Used to be the theory was that bottom rad hoses had springs in them to prevent collapse under high rpm situations when a partially clogged rad might restrict coolant flow and the water pump was trying to suck it out of the rad faster than it could be returned. So yes, that is the purpose of the spring, but different situation.
     
  7. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    Recently bought a OEM Merc water pump hose and it had the spring.
     
  8. J.Wilt

    J.Wilt Active Member SILVER Sponsor

    919
    Jan 29, 2010
    W. Mich. / Lake Michigan
    420 Sundancer 2005
    Cumming 6cta V Drives
    Highfield 310 , 20hp Suzuki
    My port side collapses about half that much, starboard side is fine.
     
  9. techmitch

    techmitch Well-Known Member GOLD Sponsor

    May 1, 2008
    Chesapeake Bay, Middle River/Frog Mortar Creek MD.
    1999 270 DA
    Twin 4.3s W/Alpa I Gen II's
    1 bad cap?
     
  10. scooper321

    scooper321 Well-Known Member

    Jul 4, 2015
    Baltimore, MD
    2003 Sea Ray 400DB
    Twin Cummins 6CTA-8.3
    mine too. I know my cap has a worn gasket. I need a new cap. I’m going to replace the hose, too.
     
  11. gmacd81

    gmacd81 Active Member PLATINUM Sponsor

    184
    Sep 2, 2014
    Annapolis, MD
    2002 460DA hardtop, Raymarine eS128 & eS75, Evolution AP, SHD color radar, Ray260
    Walker Bay w 40hp
    Cummins 6CTA M3's, Onan 11.5 kW genset
    Very normal with the 6CTA due to the design of the overflow. The tank is so far away and below the coolant reservoir, and has such a small hose, that the pressure needed to pull coolant back up is pretty high. Unless it is brand new and very stiff, the larger hose collapsing is an easier pressure relief. My mechanic pointed that our and suggested moving the overflow otherwise it's largely ineffective.
     
    Chris-380 likes this.
  12. Woody

    Woody Well-Known Member PLATINUM Sponsor

    Nov 20, 2007
    N. Wisconsin/Lk Superior
    2005 420DA
    Cummins 6CTA8.3
    My port engine does that. I put new radiator cap and new hose on, it still does that.
     
  13. scooper321

    scooper321 Well-Known Member

    Jul 4, 2015
    Baltimore, MD
    2003 Sea Ray 400DB
    Twin Cummins 6CTA-8.3
    Anyone have a link for the radiator cap? Going to Amazon yields a gazillion and I’m not interested in process of elimination.
     
  14. HP12Sea

    HP12Sea New Member

    7
    Nov 2, 2020
    Cabo now '05, Cummins QSC's, Furuno, Westerbeke 7.6
    Cummins QSCs
  15. Riptide III

    Riptide III Active Member

    668
    Dec 8, 2007
    Dartmouth MA
    1997 Sea Ray 400DA
    Cat 3116 TA
    1994 Sea Ray Laguna CC 250 Tohatsu
    :
    Mine do that also mechanic said it is common. Cap had no effect 9n mine.
     
  16. Joint Custody

    Joint Custody Well-Known Member PLATINUM Sponsor

    489
    Sep 20, 2017
    Lake Powell Utah
    2001 460 Sundancer
    Twin Cummins 6CTA8
    Thanks all. I will look into the caps. Good to see it is a common issue.
     
  17. Blueone

    Blueone Well-Known Member SILVER Sponsor

    Jan 24, 2007
    Lake Erie, Ohio
    2004 420 Sundancer
    Cummins 6CTA 450's
    If it was common I would have the problem...I am never special
     
    techmitch likes this.
  18. SKybolt

    SKybolt Active Member GOLD Sponsor

    416
    Nov 11, 2014
    Kent Narrows, MD
    1988 460 EC
    Detroit 6v92TA
    Low profile
    Alison Gears
    Westerbeke
    12.5kw Genset
    The correct cap, besides the right pressure, has a small 1/2" or so sized washer like stem with an o-ring between it and the cap. It has a small spring that holds it tight. When the system is pressurized that is held in place by the pressure, but when the engine cools down it allows coolant to return to the system from the overflow bottle by the vacuum created by the coolant shrinking in size when it's cooled.

    If the hose gets soft, as mentioned above, it will collapse and not bring as much coolant back into the system. A collapsed hose is NOT normal, it may be a bad hose design and needs the spring to allow the coolant back into the system. Whether it came from the factory that way or not, I would find a spring to place in the hose.
     
    Last edited: Nov 23, 2020
    techmitch likes this.
  19. techmitch

    techmitch Well-Known Member GOLD Sponsor

    May 1, 2008
    Chesapeake Bay, Middle River/Frog Mortar Creek MD.
    1999 270 DA
    Twin 4.3s W/Alpa I Gen II's
    "A collapsed hose in NOT normal"
     
  20. All's Well

    All's Well Active Member PLATINUM Sponsor

    907
    Jan 14, 2010
    Houston
    '12 58 Sundancer
    900 MAN
    My 6CTA's did that on my 460 the entire time that I had the boat. I replaced caps, hoses and it stayed the same. After a couple years I didn't give it any further thought, the boat ran great and never had an issues.
     
    Jaws likes this.

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