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  • S2 ABY Over heating at idle

    I bit of history, my car in a MY94 ABY Avant with 195k and coming up to 3 yrs of ownership.

    First year of ownership the car was dried stored on axle stands, Feb last year she was sent off to my trusted VAG mechanics to get her back on the road, parts included;

    Head removed, skimmed and pressure tested.
    New Head Gasket
    New Thermostat
    New Waterpump
    Cambelt replaced

    Car was trailer backed after this work, and the first thing I noticed was that the Coolant Header Tank cap was hissing once the vehicle was running.


    https://youtu.be/vQpDWL2dovA

    New Header tank and cap fitted by myself.

    Off to garage 2 to understand why coolant system is boiling over.

    Vehicle returned after 2 months, and the following ruled out as possible causes;

    heater matrix failure
    block sniff test

    Vehicle still over heating and garage think it down to a corroded coolant journal causing leak inside block, advised to run rad weld or alternative through system but decline.

    Off to garage 3, who pressure test coolant system, to find a small pin prick in the small coolant return hose between rad and coolant header tank, return hose trimmed to remove damaged part.

    Off to exhaust specialist to get sport CATS fitted so that I'll pass MOT.

    During MOT earlier this year, she failed on CO2 emissions and that fact that the car boiled over on fast idle for said test. I put failure down to new CATS with limited mileage, vehicle taken to friend MOT tester, where 2 further fast idle test were down, without boiling over, but still no emissions pass.

    Over the past month, I've started to use the car daily in the evenings, and notice that the car gets very hot when idling in traffic, but not once moving, as the air flow above 40 mph seems to cool things down again.


    Coolant level at cold

    Coolant level once started

    Main Radiator Condition

    Aux Radiator Condition

    Coolant Temp when not stuck in traffic

    Oil Temp once coolant is up to temp

    Coolant Temp when idling for 5 minutes

    Coolant Temp once moving above 50 MPH

    Coolant level after 30 minute drive and engine just switched off



    https://youtu.be/D6IzOZ4AlG8
    Coolant Header Tank return flow rate when engine is cold

    https://youtu.be/R3xVCookSrw
    Coolant Header Tank return flow rate when engine is warm

    https://youtu.be/7GowMIKcH6Y
    Engine coolant temp increase at idle

    https://youtu.be/AyhzuW7DSpg
    Engine coolant temp increase in traffic

    The options as I see them are;
    • Get existing rads re-cored to see if that fixes matters.
    • Remove spark plugs to see if any signs exist of coolant making it's way to the cylinders.
    • Perform oxalic acid radiator flush or add dishwasher tablets to coolant system and flush.
    • Add Rad weld or similar to coolant system.


    Any suggestions or ideas as to what my problem could be as you can see from the videos, the raditor fans are kicking in at the right point, and the after run procedure is working once the engine has been stopped and key removed from the ignition ?

  • #2
    My AAN also loves to get hot in the city or when idling a lot. Once you get going the temps are normal. As I understood it's natural for these engines.

    There's a trick to get your aux fan turn on a lot sooner than 110 degrees. Here it is - http://www.audiworld.com/forums/audi...ature-2153537/

    Comment


    • #3
      Originally posted by RichLV View Post
      My AAN also loves to get hot in the city or when idling a lot. Once you get going the temps are normal. As I understood it's natural for these engines.

      There's a trick to get your aux fan turn on a lot sooner than 110 degrees. Here it is - http://www.audiworld.com/forums/audi...ature-2153537/
      No tricks needed.... if car is running as it should idle temp will be fine
      RS 2 580HP

      Comment


      • #4
        I didn't catch something. Do you have to top up the coolant after drives? Or the coolant drops and then goes back up when cold?

        After a similar big rebuilt my main rad core was more than 70% blocked by coolant that had just become solid. Externally it looked ok. One thing is to try and see the top and bottom of your radiator when idling and hot to see if they are the same temperature. Use a laser temp gun or being very careful feel the core by hand. Mind the fan!

        Comment


        • #5
          Originally posted by A80Avant View Post
          I didn't catch something. Do you have to top up the coolant after drives? Or the coolant drops and then goes back up when cold?
          In the last 2,000 miles, I've had to top about half a litre of water into the coolant, from the other threads I've read, the drop in level is due to the the build up in pressure.

          Occasionally, then giving it the beans, I get the faint whiff of the sweet coolant into the cabin, so I think there is a leak somewhere, but just don't know where.

          Good call on the laser thermometer, think I'll nip down to Maplins to see what they have as I've just been out and tighten the alternator belt, and in doing so I noticed that the AUX rad lower hose felt rather empty, though removing the bottom hose from the AUX rad saw plenty of coolant coming out.

          Comment


          • #6
            Well topping up is also something to look into besides the cores.
            Re-coring the aux is easy. The main I'd just get a new one. They are around 180£ for an original one. So once it's out you can have a better look at hoses.

            I hope you don't have a gasket issue or something else so do check spark plugs

            Comment


            • #7
              Dont forget to check the turbo coolant hoses, the short one that goes from the water rail to the hard pipe round the front of the engine is almost impossible to see, change it anyway when you change the rad.. Check the water feed line to the turbo and the drain line which goes back to the block.

              Also have a good look at the after-run pump but be careful, it's made of plastic and can fall apart and spray you with hot coolant.

              Buy a new rad from Audi, it's a worthwhile investment.

              Fan first stage should come on at 90 I think

              S2 Coupe 3B Project


              Ur quattro restoration

              S2 Avant

              Boost is the new rock and roll!
              sigpic

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              • #8
                As above I would start by checking for a blocked rad and I also think you have some air in the system given the significant changes in coolant level.
                Can't believe your garages didn't bother to check this
                Remove both rads and check the flow rate through them with a hose. Whilst they are off change the turbo coolant return hose as Newsh suggested.
                Panthero Coupé quattro 20vt
                Indigo ABY coupé
                Imola B6 S4 Avant

                Comment


                • #9
                  A lot of us in the UK run high power cars without the aux rad. Just take it off and plug the 2 hoses. Fit a new main rad, job done.

                  S2 Coupe 3B Project


                  Ur quattro restoration

                  S2 Avant

                  Boost is the new rock and roll!
                  sigpic

                  Comment


                  • #10
                    Maybe the flow in the radiators is poor

                    Comment


                    • #11
                      In addition to the above have you check the thermostat is opening as expected and isn't sticking
                      Greg

                      S2Forum.com Administrator & Webmaster

                      '93 Coupe with a few tweeks

                      Comment


                      • #12
                        if you have coolant coming out of the header tank with the cap on, then you could have an issue such as cracked head, or head gasket issues.
                        Just because you have had it tested and replaced the head gasket does not mean you are 100% sure.
                        You need a garage, and have it tested for co2. Should not cost much, and you would rule out these possibility's.
                        I had this issue several years ago. A new head gasket etc did not cure it
                        The problem was corrosion of the waterways in the head caused by the wrong coolant being used at some point.
                        This allows gas from combustion from the cylinders to get into the waterways , and pressurise the system.
                        You have to remember these alloy heads are over twenty years old now.
                        So Get it tested. I sincerely hope it is not your problem, but its where you need to start. Before you end up chasseing other possibility's.
                        Good luck

                        Comment


                        • #13
                          Sorry just reread the thread, and I have given you second hand advise
                          Hope you get it fixed.

                          Comment


                          • #14
                            You might have an air lock as above, raise up the expansion tank as high as possible and bleed the system.

                            Is the rad fan working and wired in the correct way around? It should be pulling air through the rad, had very similar issues with a fan spinning the wrong way.

                            Comment


                            • #15
                              Mine used to do exactly this when it had a coolant leak. A new header tank & after run pump fixed the issue...although getting all the air out proved to be a right d!ck
                              Don't look but have a feel underneath the after run pump and see if its wet. My one looked dry from above but was dripping out underneath the pump.
                              Hopefully its just a small leak somewhere

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