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  • Overheating Issue

    Hello, I have 2012 cobalt with Volvo 8.1gic-q overheating. Help!! This is the 400 with cats.

    I have changed the impeller, the thermostat, the sensor in the thermostat housing and in the back of the engine. I have good flow from the water pump, and freshwater system.

    With and infrared thermometer I have checked the temp when it is running at low and high RPMs. Up to 1480 RPMs it stays around 150-165 (thermostat opens at 160. Over 1500 rpms it starts to overheat. The top of the port side head is the hot spot at 206 all hoses water pump and freshwater intake are 108-145. The exhaust is 185 and increases with run time 205 or so. I don’t let it get any hotter. Also engine goes into limp mode.
    engine information old impeller

  • #2
    Steve212 I moved your hi-jack of the other thread to here. I left the quotes alone so they left context to the other thread. If you want to add any further information to this new thread so people can help you, have at it. I hope someone can have some answers for you.

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    • #3
      I'll assume the impeller in the pic is the bad one

      Does the pump housing have any grooves in it?
      If there are grooves it will not be able to move as much water.

      Get a piece of 1 1/4 inch clear hose at the hardware store, barbed hose fitting and couple clamps.

      Remove the hose going into the thermostat housing from the water pump. Attach the clear hose to thermostat housing and hose. Start motor and look for bubbles.

      If you find bubbles, your sucking air somewhere or the pump is making them
      94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
      95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
      07 Seadoo GTX
      Merc Adults Only VP Adults Only
      G-Dad always said "First Liar doesn't stand a chance"

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      • #4
        Have you inspected the raw water side of the heat exchanger?
        Kenner, Louisiana 1980 Donzi 18'. 2+3 6.2 MPI Alpha 1

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        • #5
          Thanks for the input.

          I picked up the clear hose today and will work on bubbles tomorrow.
          The impeller is the old one. The picture of the housing has the new one in place.

          I'm not sure that I have a heat exchanger.

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          • #6
            In post 1 you said that you have a fresh water system. So that means that you have a heat exchanger. Try to post a picture of the top of your engine.
            Kenner, Louisiana 1980 Donzi 18'. 2+3 6.2 MPI Alpha 1

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            • #7
              Installing hose now. Pictures attached. When I said fresh water it pulls water from stern drive and is not a closed system. Also it has a flush tube you attach a garden hose. Thanks for the input and patience.

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              • #8
                Not sure, but thing on the starboard side front looks like a HX. The things on the port side top appear to be Antifreeze and Power Steering

                Not real sure

                Click image for larger version

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                94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
                95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
                07 Seadoo GTX
                Merc Adults Only VP Adults Only
                G-Dad always said "First Liar doesn't stand a chance"

                Comment


                • #9
                  Thanks, I had that out cleaned all of the lines in. Replaced the sensor and thermostat and is still overheating.

                  I did the clear hose bubble test and I do have bubbles in the line. I checked all hoses and clamps, tightened a few, still have bubbles and still overheating.

                  When I opened the water drainage plugs the port side had black grains of rubber, like sand is there anyway to flush the motor? I'm a couple of try's away from taking to a shop and mortgaging the house to pay for it. You have to have priorities! Thanks for your input

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                  • #10
                    is there anyway to flush the motor?
                    Nothing easy, but can remove the drain plugs and flush water up inside them, then let it drain back out. Normally if the pump is operating at full capacity the pump will flush the block in an hour of running or so

                    With bubbles its either the pump housing, the power steering cooler or the outdrive top connection

                    Did notice in the parts breakdown that this motor has 2 addition thermostats which are used to control the heat of the catalytic converters. They are on top and next to each exhaust

                    https://www.marinepartseurope.com/en...t-7748530.aspx
                    94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
                    95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
                    07 Seadoo GTX
                    Merc Adults Only VP Adults Only
                    G-Dad always said "First Liar doesn't stand a chance"

                    Comment


                    • #11
                      I replace the thermostat on the port side and that corrected what appeared to be a problem as it was getting over 210 while the other side was 165. THE crazy thing is before I replaced the sensors it appeared the over heating problem was corrected and it was just the sensors. Now its overheating.

                      Tonight I'll check the hoses and flush the motor. Hope I message back that it worked. Thanks for the ideas.


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                      • #12
                        Have you removed the exhaust to see if your plugged up in the CATS? They have water ports in the top and bottom and if one of them is getting plugged up, You'll still think you have decent flow from the volume of water coming out of the exhaust ports at the drive, but it isn't enough. How hot is the exhaust getting?

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                        • #13
                          I have not checked the exhaust as the exhaust is not heating up. I flushed out the motor with a garden hose through the drain plugs both sides, not sure if that matters, and took the boat out. At 1400 to 1500 no heating issues at 1600 it started to heat up. I was on my way to the marine shop and once in sight I opened her up to 4000-4400 RPMS, no heating issue!!!!
                          Got back down to idle and all is good.
                          So it was either the block was clogged or a combination of items
                          replaced the impeller it was bad
                          Replaced thermostat
                          Check all hoses for good flow
                          Replaced CAT thermostat
                          Flushed the engine (seemed to be what worked.

                          I took it into the shop so they could check it out. Make sure I didn't miss anything. They found a cracked plastic hose coupling coming in from the hull $15.00 part that could have caused major heating problems but wasn't the problem this time around.

                          Thanks to everyone on the sight for you ideas and input!

                          Happy boating

                          All the best, Steve






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                          • #14
                            Been following your posts. Glad to hear its up and running again. In your first post you said that it is a 2012 with cat engine. Could you tell me if the manifolds, elbows and cats are the original and how many hours are on them. Just trying to find out how long they last as I have a 2015 cat engine. Thanks in advance.

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                            • #15
                              Sign up today
                              It is a 2012 Cobalt with 180 hours on it. Both local marina's told it wasn't the cats unless I had really really bad luck.

                              Everything is original and is working great. Rubber bellows included. Marina checked out the boat for me (peace of mind)

                              Marina said the boat and engine are in great shape. hope this helps

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