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KA overheats even after throwing a bunch of new parts at it.

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  • KA overheats even after throwing a bunch of new parts at it.

    First, let me say this is a relatively "young" KA, not as tired and worn compared to many out there you see in tired 240s. It also feels like it pulls harder than any 240 i've driven in the past, even with the issues.

    anyway, i've been "restoring" the car to make it a reliable street/hpde car.

    new parts list:
    water pump & belts
    thermostat (personally tested)
    coolant hoses
    coolant temp sensor
    02 sensor
    one weak injector replaced (used ohm test to diagnose)
    plugs, cap, rotor, wires
    (plugs looke normal as far as i can tell)
    Also replaced the mechanical fan with electrical fans
    Also running distilled water with no coolant.

    Anyway, seems like i can drive the car just fine lightly will idle for a while with no symptoms, but if i start to push it, it will start to overheat.
    upper radiator hose gets really hard, lower hose not so much. (brand new radiator)

    I've burped the system at least 3 times for more than 30min. using this handy tool

    But bubbles still seem to pop up each time i bring it to operating temp.

    I hooked up a pressure tester and tested the system to the cap rating.

    With everything I've eliminated so far, what else could it be?

  • #2
    What kind of radiator/thermo are you running? OEM water pump?

    I ALWAYS have a hard time burping my cooling system (I'm planning on installing a swirl tank soon), but the tried and true method is to lift the front end of the car up (I get the front wheels on a driveway if I'm lazy) and let the engine idle a bit until the thermo opens. I do this once, then drive around, then get back up on the driveway and that usually gets all the air out. That kit you bought is nice, but it won't get all the bubbles trapped in KA's.
    - Phil
    1995 240sx | KA24DE-T 309whp, 368lb-ft


    • #3
      Oem water pump, oem equivalent radiator (not an aftermarket aluminum one) mishimoto 60 degree thermostat.

      I thought replacing the radiator actually did the trick at first. the old one i think was partially clogged because it was hard to get all of the old yuck out of it.
      so it's a little better with the new parts, but not resolved.

      I wasnt thinking head gasket because no other head gasket symptoms, but i think tomorrow i'm gonna see if maybe the cat is clogged. that could do it, cause it to run hot after the car has been running for a while and pushed and why it's a little better now that the parts are all new.


      • #4
        Maybe a blockage in the motor? Hose routing incorrect? Faulty radiator cap? Bad new water pump? Or as mentioned big air pocket?


        • #5
          Speaking of issues bleeding coolant systems, the VQ35 is notoriously a royal PITA to bleed effectively. Forget that monster funnel technique. I ended up purchasing this:

          and will never fill and bleed a coolant system the traditional way ever again. It's amazingly simple and effective. It worked perfectly the first time. Tstat opened right away at temp and I didn't burp a thing. Even though your issue may not be that, sharing a great tool out there for difficult to bleed engines.
          Core4 Motorsports
          CLICK HERE for Wilwood FSL6R Radial Bracket & Rear Wilwood BBK GROUP BUY
          S14 VQ AER Endurance Racing Team


          • #6
            Sounds very much like a head gasket to me. Many times they will blow just enough to allow combustion leakage without burning any coolant. If you have the car running with the radiator cap off and you see bubbles popping up it's most likely a bad head gasket in my experience. That funnel you got makes it even easier to see the bubbles too.
            98 240SX SCCA STUish


            • #7
              Sounds like bad head gasket and or warped head.
              '18 Chevrolet Volt - Electric fun hatch for DD duty!

              DefSport Koni Sleeve and Spring Perch Buy!!!


              • #8
                Do a compression & leakdown test.

                That funnel is great when you have combustion gasses entering the coolant and you can see bubbles in the funnel. But dad tried that and couldn't find anything on his car.
                Turned out he was detonating and broke ring lands on 2&3. Tons of oil blowby and it was running hot, but nothing in the coolant.
                Originally posted by SoSideways
                I don't care what color they are as long as they are LONG AND HARD.
                '04 G35 Sedan 6MT- The DD
                '96 240SX- The Track Toy


                • #9
                  Originally posted by glitched View Post
                  thermostat (personally tested)
                  Originally posted by glitched View Post
                  mishimoto 60 degree thermostat.
                  I refuse to use anything but OEM Nissan thermostats on KA's after many many issues. Parts store units brand new in box testing fine on my stove wouldn't work in the car. OEM unit fixed all those issues immediately.

                  Any time I had a head gasket go, it would normally bubble the coolant if i blipped the throttle with the radiator cap removed. Obviously do this test before its fully up to temp. A useful test if the oil isn't being contaminated.
                  '95 240sx