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  • SR20DET Overheating Need Input

    Hi all,

    I've had overheating problems with my S13 with an SR lately. I am only able to do one hot lap at a time on the track before the coolant temp reaches 100 deg c (sorry aussie temps) and keeps climbing quickly if I push on, and it also overheats on the highway if I sit at over 3000rpm, as in temps will slowly climb above 90 and keep climbing unless I slow down.

    The car used to run fine and didn't overheat, I used to be able to run 20min sessions with coolant under 90 deg c. So this started happening after I changed some things,
    - changed to thermo fan
    - removed heater/ac systems/coolant lines under intake manifold

    Then I drove the car and forgot to turn the fan on so it overheated and hit 120 deg c (dunno what that is in F).

    The engine is an S13 SR20DET
    - stock bottom end
    - Tomei head gasket
    - ARP head studs
    - Tomei cams
    - EFR 6758
    - all heater lines/ac deleted
    - 52mm alloy rad / large oil cooler
    - some basic ducting

    What I've checked/replaced:
    - replaced head gasket/checked block for flatness/machined head
    - thermostat replaced and confirmed working
    - confirmed no blockages in radiator or in engine cooling passages
    - cylinder leak down test is fine, no problems there
    - no coolant leaks
    - car is not burning coolant, level stays the same
    - cooling system pressure test is fine
    - water pump is fine, looks brand new
    - confirmed thermostat opens and water flows through the system


    Sorry for the long winded story, but I'm stuck and don't know where to go from here! Next thing I think would be take the head off and inspect for any cracks in the combustion chambers.

    Any ideas guys?

  • #2
    Did you install thermostat with the hole on top? You could have a big bad air bubble.

    Id suggest air flow as somethig missing from your list but If it didn't overheat before then it should be fine.

    Comment


    • #3
      Originally posted by jfryjfry View Post
      Did you install thermostat with the hole on top? You could have a big bad air bubble.

      Id suggest air flow as somethig missing from your list but If it didn't overheat before then it should be fine.
      Yeah thermo is in the right way, and I've bled the system a few times. I suppose its possible there's an air bubble but I'd say its unlikely.

      As for air flow, its possible, but I don't think so. We tested the temp of coolant coming out of the rad, it seems to be cool enough,.like 50deg when input in 85deg

      Comment


      • #4
        Then it sounds like something you checked as ok isn't.

        Try squeezing the upper hose while running and releasing - check for a good surge. Also run with no thermostat and see what, if anything, changes.

        Comment


        • #5
          a 35 C / 95 F drop in coolant temp from inlet to outlet of the radiator is seemingly out of the realm of reality.

          Sounds like you have a coolant flow or coolant path issue or just simply an air pocket.

          How did you bleed the system?? Did you remove the coolant plug from the outlet pipe, raise the car up, fill coolant and run car up to thermostat opening and constantly add coolant and bleed system??

          Comment


          • #6
            Did you just loop the heater lines? If so, that's your issue. I think completely blocking them can cause some bleeding problems, so I'd recommend to step the hose down really small, or block the hose somehow with a plug and maybe a 1.5-2 mm hole drilled in it to bleed air.


            Betting that's your issue.
            '18 Chevrolet Volt - Electric fun hatch for DD duty!


            DefSport Koni Sleeve and Spring Perch Buy!!!
            http://www.nissanroadracing.com/showthread.php?t=5902

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            • #7
              My heater hose is looped with no change after doing so.

              Comment


              • #8
                Well, it bypasses coolant around the radiator, so I wouldn't say just because it works for some people it's fine.
                '18 Chevrolet Volt - Electric fun hatch for DD duty!


                DefSport Koni Sleeve and Spring Perch Buy!!!
                http://www.nissanroadracing.com/showthread.php?t=5902

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                • #9
                  Originally posted by RalliartRsX View Post
                  a 35 C / 95 F drop in coolant temp from inlet to outlet of the radiator is seemingly out of the realm of reality.

                  Sounds like you have a coolant flow or coolant path issue or just simply an air pocket.

                  How did you bleed the system?? Did you remove the coolant plug from the outlet pipe, raise the car up, fill coolant and run car up to thermostat opening and constantly add coolant and bleed system??
                  The temps were just measured with an IR thermometer, so possible the outlet temp is not that accurate, since the surface temp I think wouldn't get as hot.

                  As for bleeding the cooling system, I jacked up the car as high as I could at the front and let it bleed for about 30min. I have repeated this 3 times since I also thought it must've had an air lock inside the engine, but no change now.

                  I should add that this problem has occurred at the last two track days, and for about 3 months now.

                  Here's how my heater lines are setup. They are chopped and caps welded on to cap off the lines, where the black smudges start.

                  Comment


                  • #10
                    Also my friend has this exact heater hose setup on his car with no issues, he even runs a smaller radiator than me.

                    Comment


                    • #11
                      Originally posted by Def View Post
                      Well, it bypasses coolant around the radiator, so I wouldn't say just because it works for some people it's fine.
                      Let me clarify:
                      I removed my heater core and connected the lines that would normally "loop" through the heater core. Maintained my iacv lines and eliminated my tb lines.

                      Comment


                      • #12
                        I know it goes without saying, but usually the problem is from whatever you touched right before the problem started...if it was rerouting hoses, then that's certainly a good place to triple check.

                        HVAC controller off / set to neutral?
                        Remove a/c condensor?
                        Water-cooled turbo, any noticeable differences on/off boost?
                        Does your water temp gauge and stock gauge both show overheats, (to eliminate a bad sensor/gauge..)?
                        Overflow tank have some in it?
                        Do you fill everything with straight water or antifreeze w/ proper 50/50 mix, etc.?
                        Pressure is definitely ok with the rad cap?
                        97 Kouki SR 240

                        Comment


                        • #13
                          Originally posted by jfryjfry View Post
                          Let me clarify:
                          I removed my heater core and connected the lines that would normally "loop" through the heater core. Maintained my iacv lines and eliminated my tb lines.
                          Exactly, that is bypassing hot coolant around the radiator, so your flow rate through the radiator drops.

                          It's fine to have that setup for a heater core, as the valve is closed when you don't want heat, and if you are running the heat, it's really dropping the temperature of the coolant in that circuit (and the ambient temp is likely cold anyway).
                          '18 Chevrolet Volt - Electric fun hatch for DD duty!


                          DefSport Koni Sleeve and Spring Perch Buy!!!
                          http://www.nissanroadracing.com/showthread.php?t=5902

                          Comment


                          • #14
                            If a car is dependent on the heat exchange through the heater core to not overheat, then it needs a more efficient cooling system.

                            Owner is right and I jumped ahead of proper diagnosing procedure:

                            If everything is fine, then you change something(s), you should start with what you changed. As I recall, and if I am reading your pic correctly, you need to maintain flow between the lines you capped.

                            Comment


                            • #15
                              Originally posted by jfryjfry View Post
                              If a car is dependent on the heat exchange through the heater core to not overheat, then it needs a more efficient cooling system.

                              Owner is right and I jumped ahead of proper diagnosing procedure:

                              If everything is fine, then you change something(s), you should start with what you changed. As I recall, and if I am reading your pic correctly, you need to maintain flow between the lines you capped.
                              no what he means is that when the heater core is connected and the valve is closed, no coolant travels through the heater hoses

                              when the hose is looped, the water pump is constantly pumping a certain amount of coolant around the radiator via the looped heater hose

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