Advicve on mending thermostat cooling water leak

Discussion in 'Boat Design' started by Tharayman, Jan 13, 2021.

  1. Tharayman
    Joined: Dec 2020
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    Location: North cape

    Tharayman Junior Member

    So, the old diesel engine started leaking coolant from water pump and thermostat housing. There is a pipe connecting the two, with the thermostat housing end blinded. Probably just for temperature gauging. I disconnected everything and had a look at the pipe. Some wear, and the O-rings had a bit of damage. Swapped the O-rings and tried to recreate the pipe with some JB weld coldweld. Put everyhting back together, and had to realize it had not helped at all.

    Seems like the hole where housing meets pipe has been worn down a bit, and is not entirely circular anymore. Some fast measurements with a vernier caliper seems to prove a 0,3 mm variaton when measuring across the circle. Have applied some more epoxy to the pipe ends. Especially in the O-ring grooves, hoping to give the O-ring more sealing pressure.

    What do I do if this also fails? Getting a new thermostat housing and water pump, would be one solution, but then I would be out of play for quite a while. And as always, I want to go to fishing right now! ;)

    [​IMG]
    Photo of where some of the water is coming out
    [​IMG]

    [​IMG]
    Thermostat housing removed

    [​IMG]
    Pipe showing some wear and tear
    [​IMG]
    Pipe after some epoxying.


    [​IMG]
    Thermostat housing. Not completely circular.
    [​IMG]
    Water pump suction inlet.
    [​IMG]

    [​IMG]
     
  2. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    So, you have 4 problems.

    1. O-ring radius may be worn on tstat end
    2. O-ring radius may be worn on pump end
    3. Hole at tstat worn.
    4. Hole at pump worn.

    In order to evaluate the issue, you need to fix or verify each.

    Can you explain what force holds them in?

    The copper pipe side looks like you could jist get a machine shop to fix it right n be done with it

    The housing side less simple, it depends a bit on the answer to my question.

    the t stat housing hole seems the worst, can you find a replacement?
     
  3. Tharayman
    Joined: Dec 2020
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    Tharayman Junior Member

    They are pressed into each other. The thermostat housing is then secured to the cylinder head with 4 bolts.

    I believe I have taken care of the O-rings radiuses with epoxy. Tried mounting it just now, but I had made the radius too large, and damaged the O-ring while forcing it. Will do some more sanding down and try again!

    I believe all parts can be acquired, I just need a parts list to find the correct number for it.
     
  4. fallguy
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    fallguy Senior Member

    Honestly, those items can be repaired. But the repairs would be very expensive to do right. I'd look for new or used pieces in better condition. Then, try to understsnd why the holes would wear. Psrhaps vibration? And see if you can minimize it go forward.
     
  5. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    Is that a Volvo? Those connections were notorious for leaking. If the pipes get bend they don't line up and the o-rings can't seal the misalignment. The solution is to install a new 0-ring with silicone sealant. Epoxy is not going to work. The grooves for an o-ring has to be precisely machined.
     
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  6. Tharayman
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    Tharayman Junior Member

    Sealant like Hylosil? As the water pump is pretty strong the sealant should be able to cure before starting. But surely the O-rings must be flexible enough to seal some misalignment? A friend of mine suggested that I got hold of thicker O-rings to solve the problem! I don`t know how thick they can get :)
     
  7. gonzo
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    gonzo Senior Member

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  8. Barry
    Joined: Mar 2002
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    Barry Senior Member

    O-Ring Design Considerations | Marco Rubber & Plastics | Custom O-Rings Supplier https://www.marcorubber.com/o-ring-groove-design-considerations.htm
    Some groove design information.

    Simply increasing the "wire size" / "cross section diameter" of the o-ring may not work. The id and od contact surface must be smooth.

    Certainly the pressures are very small. There is a chance that if you can get a brake cylinder hone, you can smooth the inside bores to the point that an o-ring can seal.
    The pivot point of the cylinder hones must be within the depth of the housing to ensure that the bore stays parallel.

    Then get a machine shop to make you the connector. You could consider getting in touch with a Hydraulic machine shop as they may offer a solution and would more than likely
    have more experience in o-ring leakage solutions.

    Kind of a rule of thumb
    When installing the o-ring into the groove, the ring must require a very very small stretch to ensure that when compressed the ID makes contact
    When installing the o-ring into the bore, a slight interference must exist to ensure some compression of the o-ring

    You might try a softer o-ring. A low durometer valued rubber may conform a bit more to irregularities in the bore and on the sleeve.

    [​IMG]

    Others might know if a rope style gland packing might work to deal with the rough surface. Wrap an appropriate amount into the groove and force it into the bores
     
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  9. fallguy
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    fallguy Senior Member

    the rope gland sounds like a great idea for an in the field remedy
     
  10. Tharayman
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    Tharayman Junior Member

  11. gonzo
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    gonzo Senior Member

    That is how we specify O-rings for a new design.
     

  12. fallguy
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    fallguy Senior Member

    I think he said you could try a rope gland. Not that it would work. In my opinion, engine vibrations might make that a more temporary solution. I kinda wonder if your engine mounts contributed to the failures. Gonzo is an expert on the subject.
     
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