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  • Coolant fluid change. Filling it back up is not going as expected.

    Hi folks,

    I attempted my first ever coolant change today.
    The draining part seems to have gone well enough ... the coolant that came out was a nice bright shade of green and looked pretty clean and uncontaminated.

    (After doing a bit more reading on the subject, I'm thinking I might oughta try sucking fluid out of the reservoir tank).

    Since the bike had been sitting for 20 years I figured it wouldn't hurt to run a lot of distilled water through the system to flush it out a bit, especially as I was switching from a green fluid to a blue Honda fluid. I read that not all brands play nicely together (notably the "ice" stuff stocked at my local dealer). I ran the better part of a gallon of water through it to the point that the fluid coming out of the drain plug was clear.

    Now, filling it back up again with fluids is not quite what I'm expecting. I filled up the reservoir tank until it leaked a bit out of the drain tube.
    I also filled up at the radiator cap, to the top. I rocked it a bit. I also ran the bike a bit. At this point I'd say I've poured about 1.5 quarts back in, but my manual says it will take just a bit over 2 quarts. I've done the "fill with fluids, rock the bike, run for just a bit" several times. (I think if I had fully drained the bike, I'd need to use just over 2 quarts and I'm currently only at 1.5 quarts).

    The thing that seems odd is that as I try to add more fluid (trying to fill the reservoir tank to the upper line), the fluid now basically just drips straight out of the drain tube. For example, if I pour 1 ounce of fluid into the reservoir, I get 1 ounce of fluid dumping out the drain tube. I really don't think I've filled up near the top of the reservoir tank to the level it is supposed to be at.

    Tomorrow I'll try to do a better job of seeing if the res tank is actually filled up, but the tank is not terribly clear, so it's hard to see.

    Any thoughts or guidance is appreciated!

  • #2
    I had some stresses with cooling and coolant last year...

    I'd guess that the 2 quart capacity is for a completely dry and empty system - there's probably was probably still a good amount of fluid in the system after you'd emptied it?

    It may be that you're good to go, or at least to give it a run and see how it goes? I'd give it a run and then let it cool and then see if you can get anymore in.

    BTW, my understanding is that the plastic tank is an expansion tank rather than a reservoir?

    Comment


    • #3
      Originally Posted by DrPMC
      expansion tank rather than a reservoir?
      Yeah, this is an overflow tank if coolant overflows - if you look at the plumbing, there is no way for coolant to get back into the system after it reaches the overflow tank. Fill at the radiator cap, run the engine, squeeze hoses and so on to burp the system.

      Comment


      • #4
        Well actually, if you look at the tank and, the recovery line and understand how a pressurized coolant system works it actuallyu is a recovery system Think about it for a second. If it was just overflow there would be no reason to fill it with coolant right? It is a proper expansion tank. When you have hot coolant it will expand and flow out past the radiator cap, which is where the tube connects to, if it is overheating or overfilled it will overlflow and puke on the ground. Once it cools it will draw some of the coolant back in to the tube that runs along the frame rail to refill the voided coolant. All vehicles that are water cooled have had expansion tanks since whenver the pesky EPA regulated it. I don't know the specifics beyond that but the Hawk is a recovery type system.
        88 Blue Hawk GT - Under construction but rideable (guest approved)
        89 BlackHawk 2.0 - On the lift and being assembled
        90 Hawk GT (color as to yet be determined) - Still on the shelf in crates

        Comment


        • #5


          Top line branching off under radiator cap will receive coolant that is hot, pressing UP on the plunger and expelling the liquid, filling in at the bottom of the reservoir. At the top of the reservoir is a tube that is routed with the vent line and crankcase breather, bundled together near the side stand anchor point. I don't see how the coolant would get "sucked back" via that line along the frame. There are marks on the reservoir indicating fill lines though, so maybe when burped and filled, will function as described.

          Is that about correct? Also, fill the radiator first?

          Comment


          • #6
            try shaking the bike roughly side-to-side while topping up coolant. be sure to recheck fluid level under the radiator cap after the first ride.
            "It's only getting worse."


            MY rides: '97 VFR750, '90 Red Hawk, '88 Blue/Black Hawk, '86 RWB VFR700 (3), '86 Yamaha Radian, '90 VTR250, '89 VTR250 (2), '73 CB125, '66 Yamaha YL-1

            Sold: '86 FJ1200, '92 ZX-7, '90 Radian, '73 CB750, '89 all-white Hawk, '88 blue Hawk, '86 FZ600, '86 Yam Fazer 700 , '89 VTR250, '87 VFR700F2, '86 VFR700F.

            Comment


            • #7
              There is a burping procedure in the FSM.
              Acta non verba


              '88 Blue 99% stock SOLD
              '88 Restomod
              '22 Yamaha Tracer 9 GT

              Comment


              • #8
                Originally Posted by JackalHack


                Top line branching off under radiator cap will receive coolant that is hot, pressing UP on the plunger and expelling the liquid, filling in at the bottom of the reservoir. At the top of the reservoir is a tube that is routed with the vent line and crankcase breather, bundled together near the side stand anchor point. I don't see how the coolant would get "sucked back" via that line along the frame. There are marks on the reservoir indicating fill lines though, so maybe when burped and filled, will function as described.

                Is that about correct? Also, fill the radiator first?
                Yes, fill and burp. Then cycle from cold to hot, ride it around some. Make sure it is filled to the proper level and let it cool down then coem back and chekc the level. It will probably be a little lower than when you left it and you fill it to the proper level in the reservoir. The key is to make sure the bike is on the center stand first.

                It works the same as any modern car made since at least 1985 that I have been privy to The radiator cap is spring loaded but it only holds to about 15 PSI so that is more than enough pressure to overcome by vacuum when needed to expell or recover the fluid through the tube between the neck and coolant reservoir. The Hawk tank is not sealed but it uses an offset overflow to allow it to function as a puke tank and a recovery bottle

                image.png
                88 Blue Hawk GT - Under construction but rideable (guest approved)
                89 BlackHawk 2.0 - On the lift and being assembled
                90 Hawk GT (color as to yet be determined) - Still on the shelf in crates

                Comment


                • #9
                  sorry for the misspells, I just got out of surgery, lol.
                  88 Blue Hawk GT - Under construction but rideable (guest approved)
                  89 BlackHawk 2.0 - On the lift and being assembled
                  90 Hawk GT (color as to yet be determined) - Still on the shelf in crates

                  Comment


                  • #10
                    Originally Posted by rpcraft
                    just got out of surgery, lol.
                    Nothing serious I hope....
                    edit:
                    Just saw the eye thing in the car thread - heal up soon.

                    Comment


                    • #11
                      Originally Posted by rpcraft

                      Yes, fill and burp. Then cycle from cold to hot, ride it around some. Make sure it is filled to the proper level and let it cool down then coem back and chekc the level. It will probably be a little lower than when you left it and you fill it to the proper level in the reservoir. The key is to make sure the bike is on the center stand first.

                      It works the same as any modern car made since at least 1985 that I have been privy to The radiator cap is spring loaded but it only holds to about 15 PSI so that is more than enough pressure to overcome by vacuum when needed to expell or recover the fluid through the tube between the neck and coolant reservoir. The Hawk tank is not sealed but it uses an offset overflow to allow it to function as a puke tank and a recovery bottle

                      image.png‚Äč
                      I was following the FSM instructions and realize it is written poorly.
                      "Check level of the coolant in the reserve tank and fill to correct level if level is low".

                      That makes it sound like you can / should fill the reserve tank. But you don't do that, do you? :-\ You always fill it via the radiator cap. That might be plainly obvious and known to some folks, but I don't think it's written clearly for knuckleheads with poor cognition skills like me.

                      I don't see a "burping procedure" in the FSM. I just see the above info on adding the coolant and then running the bike a bit. Am I missing some other page/section of the manual?


                      In the meantime, this procedure woke me up a bit and I realized I haven't seen my temp gauge moving much and I haven't heard my fan kick on.
                      So tonight I monkeyed around with some troubleshooting steps in the FSM.
                      - fan works when I jump it
                      - gauge works when I jump it (I know this doesn't cause the fan to turn on)
                      - temperature sensor doesn't get continuity when I ground it.
                      So I think I ought to go buy a new sensor [ 37750-PC1-004 ] and install it.

                      OEM costs ~$65 from Ron Ayers, but I'm seeing generic versions of this part on amazon etc for roughly $10.
                      What's the wisdom on using generic sensor vs OEM, and do you have a link for a version that people are satisfied with?
                      (I'll be searching tonight but if you happen to know, I'd be happy to benefit from Your Wisdom.

                      Comment


                      • #12
                        Much appreciated. I'm pretty sure the worst is behind. I spent most of March and the first 2 weeks of April clinically blind. I couldn't read, watch tv, drive, and really it was very depressing initially. If I did not know where things were in my house it would have been a disaster just walking out the door. It was scary to wake up one day and not be able to see for certain. Alll the other troubles in life seem to pale in comparison when you have that happen. It was humbling to say the least. I'll never take clear vision for granted again


                        Anywho, moving on to happier thoughts... I am not personally sure how much the side stand vs center stand thing really matters. It's similar to checking the oil. I just know usually when I fill mine it is on the bike lift so on the center stand and I rarely have an issue. I am sure Honda specifies it for a reason and the Hawk is probably more sensitive to it. I think if you have an aftermarket shock the additional lean may actually affect it a little more too, so that is food for thought.
                        88 Blue Hawk GT - Under construction but rideable (guest approved)
                        89 BlackHawk 2.0 - On the lift and being assembled
                        90 Hawk GT (color as to yet be determined) - Still on the shelf in crates

                        Comment


                        • #13
                          Originally Posted by rpcraft
                          Much appreciated. I'm pretty sure the worst is behind. I spent most of March and the first 2 weeks of April clinically blind. I couldn't read, watch tv, drive, and really it was very depressing initially. If I did not know where things were in my house it would have been a disaster just walking out the door. It was scary to wake up one day and not be able to see for certain. Alll the other troubles in life seem to pale in comparison when you have that happen. It was humbling to say the least. I'll never take clear vision for granted again
                          I'm just catching up on this, too. Man, that is crazy and scary. I'm glad to hear the worst is behind you and you are getting better.
                          There are a whole bunch of gremlins out to get us ... and while these mortal bodies of ours work pretty good when we are young, they sure do break down as we get older.

                          Comment


                          • #14
                            Originally Posted by JackalHack
                            I don't see how the coolant would get "sucked back" via that line along the frame.
                            A modern radiator cap is 2 valves in one. One in each direction. Everybody knows about the first... not so much the 2nd.

                            The water jacket is sealed(ish). As water heats, it expands. A normally running Hawk will have about 7 PSI of pressure when warm.

                            When it gets too hot then the cap "blows open" and allows excess pressure to vent into the catch can.

                            When the coolant cools, it contracts. That creates a partial vacuum in water jacket.

                            The big valve in the cap doesn't let anything flow in the backward direction BUT there is a secondary valve in the same asassembly. It is small and right in the center of the cap. You can pull it open with your pinky nail.

                            That's how coolant gets back into the water jacket. The partial vacuum opens the return valve and (because the blow off tube reaches the BOTTOM of the reservoir) sucks coolant back in.

                            Before our modern days, antifreeze wasn't considered an important pollutant, so the thermostat would vent it out of a hose and onto the ground. It was appropriately called the "road vent."

                            Modern motors still have a road vent but it's on the overflow bottle... to keep it from blowing up when you have bigger cooling problems.
                            Last edited by ParcNHawk; 04-18-2023, 12:48 PM.

                            If you were looking for a support group you're barking up the wrong tree. This place is fulla enablers dude. - Shooter77us

                            The bitterness of low quality lingers long after the thrill of a low price has gone. - RacerX450

                            Comment


                            • #15
                              Originally Posted by ParcNHawk
                              A modern thermostat is 2 valves in one.
                              Do you mean "radiator cap"?

                              "I couldn't afford NOT to buy it!"

                              Comment

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