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Thread: Overheating

  1. #11
    Join Date
    Apr 2019
    Posts
    36

    Default Re: Overheating

    Quote Originally Posted by BruceK View Post
    I had a problem a couple years ago where air was being sucked into the raw water pump from behind through the shaft and bearings. Not enough to stop the pump working at low speeds but at high speeds would suck in enough air to create an air lock. Didn't seem credible at the time but once again VolvoPaul was spot on the money.
    Annually I get another issue with similar symptoms. Barnacles and fouling grow in the intake ports of the leg. It doesn't take a lot of them either before they hit critical mass. As you are on a trailer this is probably not the case, but if you left your RIB on a mooring even for a couple weeks you'll be surprised how quickly the little critters can invade and grow enough to do this.
    Hmmm I shall look into the pump.
    I have pulled out a hose which goes from the exhaust elbow to the outlet in transom,behind the leg. It has a bend but it's collapsed so much it might be restricting flow. I'm not much of a mechanic and I can't get my head around why fresh water coolant will explode out of the header tank if the raw water system is not working correctly. They are not connected 🤪 My,only slightly more qualified mechanic mate assures me it matters.
    We are barnacle free but I know what you mean. We've had trouble with them when we kept the boat in the water.

  2. #12
    Join Date
    Apr 2019
    Posts
    36

    Default Re: Overheating

    Quote Originally Posted by FARSCO View Post
    Have you recently filled the coolant expansion tank?

    Certainly on early Kad42, the tank was under sized and would chuck out coolant for fun.

    Could be as simple as a coolant cap is knackered too.
    We have been filling it regularly as it's been leaking but only to the halfway mark. Did have an issue with overheating once before which turned out to be bunged up oil cooler but before we sussed that out we changed to a new header tank and cap...I think we ended up with 3 new caps so have been swapping them about recently!

  3. #13
    Join Date
    Feb 2015
    Location
    Conwy
    Posts
    4,069

    Default Re: Overheating

    Quote Originally Posted by Wobbo View Post
    Hmmm I shall look into the pump.
    I have pulled out a hose which goes from the exhaust elbow to the outlet in transom,behind the leg. It has a bend but it's collapsed so much it might be restricting flow. I'm not much of a mechanic and I can't get my head around why fresh water coolant will explode out of the header tank if the raw water system is not working correctly. They are not connected �� My,only slightly more qualified mechanic mate assures me it matters.
    We are barnacle free but I know what you mean. We've had trouble with them when we kept the boat in the water.
    If the hose is old and soft then the vacuum draw of the pump can allegedly cause it to collapse starving the raw water feed. I have not experienced this myself but it sounds plausible enough and others have reported it. May be worth changing any old and "gone soft" rubber intake hoses.

  4. #14
    Join Date
    Jun 2012
    Posts
    77

    Default Re: Overheating

    Quote Originally Posted by Wobbo View Post
    We have been filling it regularly as it's been leaking but only to the halfway mark. Did have an issue with overheating once before which turned out to be bunged up oil cooler but before we sussed that out we changed to a new header tank and cap...I think we ended up with 3 new caps so have been swapping them about recently!

    Our Kad 42 doesn’t like the antifreeze any higher that halfway between low and half ie “quarter tank maximum “ took me ages to work this out couldn’t realise why I kept having to top up ,since only putting 1/4 tank antifreeze the level never budges all season

  5. #15
    Join Date
    Feb 2008
    Location
    Farndon
    Posts
    3,009

    Default Re: Overheating

    On my ka32s the coolant is in the low mark on the reservoir one cold engine and stable.
    If you are not seeing hight temp on the gauge sounds like you simply need to adjust the coolant level.

  6. #16
    Join Date
    Feb 2008
    Location
    Farndon
    Posts
    3,009

    Default Re: Overheating

    I intended to write .... on the low mark on a cold engine

  7. #17
    Join Date
    Apr 2019
    Posts
    36

    Default Re: Overheating

    Quote Originally Posted by Restoration man View Post
    Our Kad 42 doesn’t like the antifreeze any higher that halfway between low and half ie “quarter tank maximum “ took me ages to work this out couldn’t realise why I kept having to top up ,since only putting 1/4 tank antifreeze the level never budges all season
    Aye..there is another thread for an overheating Kad32 on this forum I read through and I did note they don't like to be filled to the mark.
    When you fill up do you bleed the air out somehow to avoid airlocks? I fill up through a hose at highest point by the turbo, not sure if I should be doing something else!?

  8. #18
    Join Date
    Apr 2019
    Posts
    36

    Default Re: Overheating

    Quote Originally Posted by MartynG View Post
    I intended to write .... on the low mark on a cold engine
    Yes I'm definitely giving this a go. Restoration man said same thing. I Can't get down until the weekend. Did start stripping bits off and poking around in hoses last Sunday on my way to the oil cooler which was the cause of trouble last time so I'll reassemble and see what happens.
    How do you fill up with coolant!? Through top of turbo?
    Thanks for all the replies 👍

  9. #19
    Join Date
    Apr 2019
    Posts
    36

    Default Re: Overheating

    Quote Originally Posted by MartynG View Post
    On my ka32s the coolant is in the low mark on the reservoir one cold engine and stable.
    If you are not seeing hight temp on the gauge sounds like you simply need to adjust the coolant level.
    The temperature shot up really quickly so we stopped, lifted the engine box just in time to see all the coolant pumping out the header tank.

  10. #20
    Join Date
    Apr 2008
    Location
    Isle of Man
    Posts
    2,069

    Default Re: Overheating

    I just top up via the expansion tank then crack the small coolant return line union on the turbo whilst running to bleed.

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