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    4788 Starboard Engine Overheats at High RPM

    Hopefully someone can help me understand how I can resolve this problem.

    The engine runs fine under 2600 RPMs. Engine temperature is around 150 - 175. At 2600 rpms, I can hear the turbos whine and around 1 or 2 minutes later, the engine light goes on. The coolant overflow fills rapidly. I idle the engine and the alarm stops in about the same amount of time (2 -3) minutes. The temp returns to around 150 and the coolant level drops. I can run the engine as long as I stay below 2600.

    One idea is that exhaust gas is getting into the coolant, driving up the temperature and pressure rapidly. Once the engine is idled, the coolant quickly cools and the pressure is relieved.

    Has anyone run into this issue before and how did you resolve it?

    Thanks

    #2
    Originally posted by Valkyrie View Post
    Hopefully someone can help me understand how I can resolve this problem.

    The engine runs fine under 2600 RPMs. Engine temperature is around 150 - 175. At 2600 rpms, I can hear the turbos whine and around 1 or 2 minutes later, the engine light goes on. The coolant overflow fills rapidly. I idle the engine and the alarm stops in about the same amount of time (2 -3) minutes. The temp returns to around 150 and the coolant level drops. I can run the engine as long as I stay below 2600.

    One idea is that exhaust gas is getting into the coolant, driving up the temperature and pressure rapidly. Once the engine is idled, the coolant quickly cools and the pressure is relieved.

    Has anyone run into this issue before and how did you resolve it?

    Thanks
    The first thing I would do is check the seawater path.

    Impeller would be first, then go downstream from there.

    A fairly common choke point is the trans oil cooler.

    KEVIN SANDERS
    4788 LISAS WAY - SEWARD ALASKA
    www.transferswitch4less.com

    Whats the weather like on our boat
    https://www.weatherlink.com/embeddab...59665f4e4/wide


    Where are we right now? https://maps.findmespot.com/s/36S4

    Comment


      #3
      I presume you have the 330/370hp version. Like Kevin suggests, you need to check out all elements of the raw water cooling system - pump impeller, aftercooler, transmission cooler and heat exchanger. Other than the pump, all devices have tubes that can get blocked with impellor bits or growth. Cruise speeds allow enough cooling water thru, but at first thought, there is an obstruction there somewhere.

      Good luck with it!

      Cheers
      John H
      Brisbane QLD Aust
      "Harbor-nating"

      2000 - 4788/Cummins 370's

      Comment


        #4
        Don’t forget the seawater pickups. They can become magnets for sea grass that gets stuck in the fins and severely restrict water flow.
        P/C Pete
        Edmonds Yacht Club (Commodore 1993)
        1988 3818 "GLAUBEN”
        Hino EH700 175 Onan MDKD Genset
        MMSI 367770440

        Comment


          #5
          Thanks for the feedback. The thru hull strainers are clean. I'll check the impellers. If there were an obstruction, wouldn't the engine stay hot once it overheated? Instead it cools down to 150 degrees or so quickly once the engine is iidled.

          Comment


            #6
            Had a similar issue, one of the raw water hoses delaminated inside, caused hose to collapse and restriction at higher RPM, would flow properly when engine RPM was reduced.

            Comment


              #7
              This forum has some very knowledgeable folks. I have personally found that you need to take all the advise into consideration and follow the suggestions. One time I had my blinders on and the advise was given but I just did not take the time to inspect the entire cooling water path. Lesson Learned

              Comment


                #8
                Originally posted by Pcpete View Post
                Don’t forget the seawater pickups. They can become magnets for sea grass that gets stuck in the fins and severely restrict water flow.
                That would do it too! Anything that restricts the flow would have the effect the OP is describing.

                KEVIN SANDERS
                4788 LISAS WAY - SEWARD ALASKA
                www.transferswitch4less.com

                Whats the weather like on our boat
                https://www.weatherlink.com/embeddab...59665f4e4/wide


                Where are we right now? https://maps.findmespot.com/s/36S4

                Comment


                  #9
                  Originally posted by Valkyrie View Post
                  Thanks for the feedback. The thru hull strainers are clean. I'll check the impellers. If there were an obstruction, wouldn't the engine stay hot once it overheated? Instead it cools down to 150 degrees or so quickly once the engine is iidled.
                  Nope...

                  Imagine the engine simply not getting enough cooling water through the heat exchanger to remove the heat.

                  Lower the RPM, this lowers the heat output of the engine, and it pretty much immediately cools back to a normal operating temp.


                  KEVIN SANDERS
                  4788 LISAS WAY - SEWARD ALASKA
                  www.transferswitch4less.com

                  Whats the weather like on our boat
                  https://www.weatherlink.com/embeddab...59665f4e4/wide


                  Where are we right now? https://maps.findmespot.com/s/36S4

                  Comment


                  • builderdude
                    builderdude commented
                    Editing a comment
                    Exactly, most overheats likely occur at higher rpm ranges and engine loads due to a seawater flow restriction.

                  #10
                  Thanks again for all the feedback. I'm planning to do an overhaul of my cooling systems this Winter. One question we have is how is the Heat Exchanger Core removed on a HINO WO6D-T1? Will I need to remove the Heat Exchanger to get the core out?

                  Comment


                    #11
                    Most likely you'll need to remove the heat exchanger,however the good part is now it can be ceramic coated and tube bundle cleaned. Use a good heavy duty diesel Antifreeze (I use Fleet Guard) and change every 3 years.
                    Brad & Sharon
                    Lady Jake
                    1985 4550 EH 700TI /Twin Disc 502
                    Anacortes/La Conner, Wa.

                    Comment


                      #12
                      Parts and service manual is here...
                      Hino and US Marine | Marine Parts Supply

                      An older writeup is attached here....
                      Hino Manicooler remove-replace.pdf

                      Northport NY

                      Comment


                        #13
                        Terrific. Thanks

                        Comment


                          #14
                          Had a similar (?) problem. 150 Hinos. Starboard engine would produce steam from the exhaust above 2000 rpm. Didn’t get any overheating indications. Possibly because once I saw the steam I backed off and chugged back to port at low speed. Strainers clear but, according to my diver, I had a significant buildup of barnacles on the raw water inlets under the hull. After he evicted them all is well. I worked out that it was Inlet blockage by removing the tops from the strainer baskets and opening the through hull valves. There was a significant difference between the port and starboard water flows. I did replace the impeller on the water pump as a precaution afterwards.

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