Skip to content
  • Recent
  • Tags
  • Popular
  • Users
  • Groups
Skins
  • Light
  • Cerulean
  • Cosmo
  • Flatly
  • Journal
  • Litera
  • Lumen
  • Lux
  • Materia
  • Minty
  • Morph
  • Pulse
  • Sandstone
  • Simplex
  • Sketchy
  • Spacelab
  • United
  • Yeti
  • Zephyr
  • Dark
  • Cyborg
  • Darkly
  • Quartz
  • Slate
  • Solar
  • Superhero
  • Vapor

  • Default (Slate)
  • No Skin
Collapse
Brand Logo

DT125R FORUM

  1. Home
  2. Technical Zone
  3. Engine
  4. Overpressure in cooling system

Overpressure in cooling system

Scheduled Pinned Locked Moved Engine
12 Posts 6 Posters 2.8k Views
  • Oldest to Newest
  • Newest to Oldest
  • Most Votes
Reply
  • Reply as topic
Log in to reply
This topic has been deleted. Only users with topic management privileges can see it.
  • M Offline
    M Offline
    MDN91
    wrote on last edited by Mightyman
    #1

    Hi guys,

    Well, it seems everytime I solve an issue with my DT, along comes another. I just replaced the piston because I struggled with piston slap - turned out to be the piston fitted when the barrel was rebored was too small - while I was at it, I fitted another 3MB head a had laying around in mint condition, moved the thermostat and housing over etc. Fired the bike up, sounds great, no weird noises anymore - however, when filling the cooling system I discovered that somehow the pressure in the system is way too high - with the cap off the radiator at squirts a large amount of coolant right out, everytime I give it some throttle, this happens from cold start and continues when the engine is hot, if I fit the radiator cap it just comes out from the coolant resorvoir instead.

    Any ideas why this happens? Only thing I can think off is a bad bottom or head gasket, but this seems unlikely as it would have to be very leaky to make this kind of issue, and I was very thorough as always.

    https://www.youtube.com/watch?v=iwrBbsG8YN4

    1 Reply Last reply
    1
    • MightymanM Offline
      MightymanM Offline
      Mightyman
      wrote on last edited by
      #2

      Man that engine does sound sweet! 😁 You shouldn't really remove that cap when the bike is warmed up as there is always going to be some sort of pressure in the system. I don't actually know if your video shows TOO much pressure though. Anyone else?

      TDR 125 - 2001

      M 1 Reply Last reply
      1
      • CalumC Offline
        CalumC Offline
        Calum
        wrote on last edited by
        #3

        As the coolant heats it expands hence pressure.

        The radiator cap is supposed to handle some sort of pressure, replacing that can sometimes fix the problem.

        If the pressure is massively undue then it is likely to be a headgasket.

        The head and barrel needs to be skimmed. They are both ally and both warp.

        Always Originate, Never Pirate!

        B 1 Reply Last reply
        0
        • MightymanM Mightyman

          Man that engine does sound sweet! 😁 You shouldn't really remove that cap when the bike is warmed up as there is always going to be some sort of pressure in the system. I don't actually know if your video shows TOO much pressure though. Anyone else?

          M Offline
          M Offline
          MDN91
          wrote on last edited by
          #4

          @Mightyman said in Overpressure in cooling system:

          Man that engine does sound sweet! 😁 You shouldn't really remove that cap when the bike is warmed up as there is always going to be some sort of pressure in the system. I don't actually know if your video shows TOO much pressure though. Anyone else?

          Yeah, I know there are supposed to be some pressure, but this is definetly too much, i've filled the system a number of times by now, and i've never noticed anything like this before 🙂

          @Calum said in Overpressure in cooling system:

          As the coolant heats it expands hence pressure.

          The radiator cap is supposed to handle some sort of pressure, replacing that can sometimes fix the problem.

          If the pressure is massively undue then it is likely to be a headgasket.

          The head and barrel needs to be skimmed. They are both ally and both warp.

          Might be the cap yes, but this wasn't an issue a month ago, before I changed the piston, so I doubt it helps changing the cap - it's more likely the head that maybe is warped yes, I didn't really check it since it seemed to be in a very good condition.

          1 Reply Last reply
          0
          • A Offline
            A Offline
            andrewj1680
            wrote on last edited by
            #5

            Looks like too much pressure to me and like calum mentions I'd say the mating surfaces need skimming, guessing you used a decent gasket?

            M 1 Reply Last reply
            0
            • A andrewj1680

              Looks like too much pressure to me and like calum mentions I'd say the mating surfaces need skimming, guessing you used a decent gasket?

              M Offline
              M Offline
              MDN91
              wrote on last edited by
              #6

              @andrewj1680 said in Overpressure in cooling system:

              Looks like too much pressure to me and like calum mentions I'd say the mating surfaces need skimming, guessing you used a decent gasket?

              Yes, used a Athena gasket kit when refitting the top end.

              Well, I'll order another gasket kit and get to it as soon as possible, hope this solves the issue, if you guys have any other thoughts, please let me know.

              A 1 Reply Last reply
              0
              • M MDN91

                @andrewj1680 said in Overpressure in cooling system:

                Looks like too much pressure to me and like calum mentions I'd say the mating surfaces need skimming, guessing you used a decent gasket?

                Yes, used a Athena gasket kit when refitting the top end.

                Well, I'll order another gasket kit and get to it as soon as possible, hope this solves the issue, if you guys have any other thoughts, please let me know.

                A Offline
                A Offline
                andrewj1680
                wrote on last edited by
                #7

                @MDN91 never used the Athenna gasket but am told they are next best thing to a genuine, I use genuine Only, I know it sounds silly but you have put the head gasket the right way up haven't you as I've seen that before too, I'm sure I've seen a tread on the site about a mild skim using a sheet of glass and cutting compound, by calum if I remember rightly

                1 Reply Last reply
                0
                • M Offline
                  M Offline
                  MDN91
                  wrote on last edited by
                  #8

                  Sooo, time for an update.

                  Turns out it WASN'T Athena gaskets I fitted, rather some chinese noname ones - I had the top end gasket kit laying around for ages (can't remember where I bought it from) and didn't look much at the package when I fitted the new parts, but now I have done the light skim of the head and barrel, fitted Athena gaskets and guess what - no more overpressure in the radiator 😄 And it feels like the compression has increased quite a lot too (duh).

                  1 Reply Last reply
                  2
                  • A Offline
                    A Offline
                    Ads123
                    wrote on last edited by
                    #9

                    Head gasket has gone mate 100% ha he that and all will be sorted 👍🏻

                    M 1 Reply Last reply
                    0
                    • CalumC Offline
                      CalumC Offline
                      Calum
                      wrote on last edited by
                      #10

                      Yeah that's the usual suspect on these bikes. I dismissed it because you said you had used an Athena gasket. I would love to build an engine with those cheap gaskets and NOT have it fail.

                      They are notoriously bad!

                      Always Originate, Never Pirate!

                      1 Reply Last reply
                      0
                      • A Ads123

                        Head gasket has gone mate 100% ha he that and all will be sorted 👍🏻

                        M Offline
                        M Offline
                        MDN91
                        wrote on last edited by
                        #11

                        @Ads123 said in Overpressure in cooling system:

                        Head gasket has gone mate 100% ha he that and all will be sorted 👍🏻

                        Yep, it sure was the head gasket

                        @Calum said in Overpressure in cooling system:

                        Yeah that's the usual suspect on these bikes. I dismissed it because you said you had used an Athena gasket. I would love to build an engine with those cheap gaskets and NOT have it fail.

                        They are notoriously bad!

                        I really believed I did use Athena gaskets, my mistake - won't do that again, that's for sure. 😄

                        1 Reply Last reply
                        1
                        • CalumC Calum

                          As the coolant heats it expands hence pressure.

                          The radiator cap is supposed to handle some sort of pressure, replacing that can sometimes fix the problem.

                          If the pressure is massively undue then it is likely to be a headgasket.

                          The head and barrel needs to be skimmed. They are both ally and both warp.

                          B Offline
                          B Offline
                          Bentley
                          wrote on last edited by
                          #12

                          @Calum wow 😳 you've got some good knowledge!!!

                          1 Reply Last reply
                          0
                          Reply
                          • Reply as topic
                          Log in to reply
                          • Oldest to Newest
                          • Newest to Oldest
                          • Most Votes


                          • Login

                          • Don't have an account? Register

                          • Login or register to search.
                          • First post
                            Last post
                          0
                          • Recent
                          • Tags
                          • Popular
                          • Users
                          • Groups