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  1. #11
    Join Date
    Jul 2011
    Posts
    309

    Default Re: Engine cooling thermostat, how does it work

    Quote Originally Posted by vas View Post
    fwiw,

    my IVECOs thermostat is on the outer side of the liquid coolant heat exchanger, extremely easy to access (but being halfway up the block you tend to loose half the coolant if you try to remove it)
    They are stamped 62 or 68 (pretty sure it's 62 though) and they look like any bog standard 70-80s car thermostat.
    As part of the heat exchanger maintenance, I removed them, took them home, put them in a small pan and heated them with a decent Hg thermometer in the water, they started opening at said temp and over the next couple of mins with temp rising slowly, they opened fully.
    So, they are not on-off, but I doubt it will be easy to get a constant temp that they'll just stay slightly on (unless stuck).

    Now, mine looked brand new, but circuit is full of ready mixed coolant and I never had to add any, so I guess if yours is similarly maintained, you wont need to bother with it, just get something else to worry about (if you have to )
    Finally mine will most likely fail closed I recon judging from my cars of the era. Newer ones fail open (like wife's Sei) but not bothered removing it so no idea how these look like

    cheers

    V.
    Checking if the Thermostat works by placing in pan of water and heating, I think that the stated temperature is when it reaches fully open

  2. #12
    Join Date
    Feb 2015
    Location
    Conwy
    Posts
    3,878

    Default Re: Engine cooling thermostat, how does it work

    I stand to be corrected but as the wax melts at a certain temp the valve will only open and quite quickly at that temp. My KADs have two thermostats. Partially to cater for water flow I presume but I believe one opens at a slightly lower temp than the other. This I think controls the all on or all off tendency.

    I may be talking complete BS here mind, just repeating what I have been informed when I raised a similar question.

  3. #13
    Join Date
    May 2001
    Location
    Bucks & St Raphael SoF
    Posts
    1,398

    Default Re: Engine cooling thermostat, how does it work

    Quote Originally Posted by Portofino View Post

    On engines with belt driven pumps like the MTU 183, it is of the upmost importance to perform regular visual inspections. On the MTU 183, the raw water pump and coolant pump are belt driven and since belts crack and stretch, it is critical to have them in good working condition. Due to atmospheric conditions and leaks, the pulleys can also rust and can cause a premature failure of the belts as with VP KAD series.
    Thankfully the belts are easy to check and very easy to change too!

  4. #14
    Join Date
    May 2001
    Location
    Jersey/Antibes
    Posts
    22,435

    Default Re: Engine cooling thermostat, how does it work

    Quote Originally Posted by MapisM View Post

    So, just to double check, is my understanding correct that the thermostat has bugger all to see with the raw water, which goes through all its intended routes regardless of engine temp? I mean, does raw water always pass through heat exchanger/aftercooler/gearbox HE/manifolds (and eventually expelled, mixed with the exhaust) regardless of any temperature?
    Exactly correct MapisM. The thermostat only regulates the flow of the jacket water circuit (=freshwater/antifreeze circuit). The raw water circuit is not affected by the thrmostat (though is affected by RPM)

  5. #15
    Join Date
    Nov 2007
    Location
    Boat Orwell - Me Norwich
    Posts
    7,688

    Default Re: Engine cooling thermostat, how does it work

    Perhaps not relevant to mobos, but many sailing craft have direct (seawater) cooled engines, and no freshwater coolant or heat exchanger. The thermostats for direct cooled engines open at a lower temperature to those for indirect (freshwater) cooled engines (even the same model engine). The freshwater cooled ones run at a higher, more efficient temperature, but at that temperature salt etc. is precipitated out of the seawater (and its not pressurised) so they're run cooler. I'm not certain, but IIRC the thermostat for the indirect (freshwater) cooled version of my engine (Bukh 36) opens at 90 degrees, whereas the thermostat for the direct (seawater) cooled version opens at 75 degrees. It doesn't pay to have the wrong thermostat!

  6. #16
    Join Date
    Mar 2002
    Posts
    17,265

    Default Re: Engine cooling thermostat, how does it work

    Quote Originally Posted by LittleSister View Post
    Perhaps not relevant to mobos, but many sailing craft have direct (seawater) cooled engines
    Interesting. I wasn't aware of raw water cooled diesels.
    That is a rather common solution in petrol engines though, albeit only up to a point.
    For instance, I've had two boats powered by the Mercury 350 cid small blocks, and they had no closed circuit.
    But my 496HO powered boat did have it, as well as higher power engines do, all the way up to the 552 cid 1750hp twin turbo monster built by Merc Racing.

    All that aside, just for the records, my main reason for posting this thread was a sanity check, sort of.
    In fact I found myself wondering, while flushing the engines with fresh water the day after I used the boat (hence with cool engines), whether by running them at idle for a short time I would really flush the whole raw water circuit or not.
    Reason being that reaching the operating temperature at idle with no load is almost impossible, or would take forever anyway.
    So, thanks for confirming me that I wasn't missing anything.

    Btw, there is actually a partial exception I was already aware of, and which contributed to make me wonder about others, if any.
    Just in case anyone is interested, in some MAN engines the aftercooler is split in two parts.
    The first (smaller, about 1/3) is filled with cooling liquid, and the second with raw water.
    But while the cooling liquid flows at all times, the raw water flow is controlled by a valve which opens only when the turbos begin building up pressure.
    The logic is that when running at or just above idle it's actually better to warm up a bit the air, rather than cool it down.
    So, in these engines, the raw water section of the aftercooler can only be flushed with fresh water when the engine is spinning at 1500+ rpm, which requires a pretty high capacity of fresh water supply, possibly unavailable when flushing the engine.

    Actually, there is a trick for letting fresh water flow also in the raw water section of the aftercooler, even with the engine running at idle.
    That's another story though, and very engine-specific, so I'm not going to expand further.
    Will do if anyone is interested, anyway.

  7. #17
    Join Date
    Mar 2015
    Location
    Isle of Eigg
    Posts
    7,126

    Default Re: Engine cooling thermostat, how does it work

    Seems that they are not just open/close...
    Just call me Dougal, Sir Dougal to you.

  8. #18
    Join Date
    Apr 2011
    Location
    Boat- Western Med
    Posts
    4,995

    Default Re: Engine cooling thermostat, how does it work

    Quote Originally Posted by MapisM View Post
    Interesting.

    All that aside, just for the records, my main reason for posting this thread was a sanity check, sort of.
    In fact I found myself wondering, while flushing the engines with fresh water the day after I used the boat (hence with cool engines), whether by running them at idle for a short time I would really flush the whole raw water circuit or not.
    Reason being that reaching the operating temperature at idle with no load is almost impossible, or would take forever anyway.
    So, thanks for confirming me that I wasn't missing anything.
    :
    Why wait the next day for them to cool ?

    Is the sea water too cold or something compared to jetty water ?
    What happens at the fuel pontoon temp diff wise ?? Once you have filled up do you wait a day before restarting

    All your coolers will drain down within minutes of shut down from seawater and the heat dwell will instantly within crystalline / crystallise any residual dry salt . Raw water runs out because the engines are higher than the WL , well the raw wet able bits are .
    By the time you have phaffed with the lines etc at the dock the engines have drained down within minutes of being off ,
    “Next day “ or next time you fire up , more so if not left for months on end , a good blast to near WOT will get the raw water dissolving that deposit away .

    After a prolonged shut down say 6 weeks I notice a 1 or 2 degree increase in jacket temp during a first hour , @ cruise say 1780 / 1820 rpm .
    After an hour that s lost its as if with the raw water pump has blasted sufficiently the inside of the tubes to flush out any deposit from the past 6 weeks that’s sat there kinda Harding up if you like .
    Obviously after 1 day or 1 week that slight temp rise does not occur .
    This phenomenon is more noticeable after the winter during its first long run out , its as if the shear vol of raw water is giving it a flush .
    This year it went from 86/87 to 84/85 within a 2 hr blast on the first run out .

    Secondly you have no anodes in any coolers ( because they drain down rendering them useless when shut down ) The anodised corrosion protection is provided by your transom anodes and the earth strap connecting that to the block .I suspect flushing through with fresh water could compromise that protection in any parts that don’t completely drain down as it needs as much electrical continuity as possible for the protective sub atomic particles the Zinc s release to transport to those areas .Residual salt water will do that better .

    This whole fresh water flush with a bodged DIY none OEM way in through a hose connection on the strainer with MAN s is nuts .

    Go the other way and regularly use them , run them as MAN intended.
    Last edited by Portofino; 18-06-19 at 05:28.

  9. #19
    Join Date
    Dec 2005
    Location
    Live London
    Posts
    3,625

    Default Re: Engine cooling thermostat, how does it work

    My heat exchangers have 2 large anodes each- d12.

    They only part drain and when you take them to bits there is a calcium tide mark that eventually blocks the lower half. Fresh flush over winter is worthwhile in my view

  10. #20
    Join Date
    Apr 2011
    Location
    Boat- Western Med
    Posts
    4,995

    Default Re: Engine cooling thermostat, how does it work

    With regards attempting to extend the cooler strip down interval by pseudo flushing with fresh water “the day after “.
    Over and above my point of a good timely blast of raw seems to do the trick , You are not addressing the oil contamination of the air side fins of the CAC or the film of crud from the closed circuit of the HE .
    Or gasket deterioration.

    Infact of the two coolers imho it’s actually the charge air coolers fins fouling up that the most serious part .
    Fortunately I can access inlet air temp / charge air temp .
    Any rise in inlet air temp has an immediate knock on effect on the EGTs .
    This is often overlooked as folks get fixated ( correctly and understandably) with fouling when thinking about overloading mitigation tactics .

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