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  • Audi S2 ABY Coupe Coolant Warning Light

    Hello,

    I've just purchased a 1994 Audi S2 ABY Coupe. I was driving home after purchasing the car (2 hour drive) and about 5 minutes away from my house, the coolant warning light comes on with the associated beeps. I pulled over into a car park and turned the car off so as not to damage the engine. The coolant gauge was normal, about 70/80 degrees, didn't shoot up. Coolant level was just below minimum but not by much and initially, the fan wasn't spinning. However, it started spinning after I pressed AC but I'm not sure why as the car doesn't have an AC belt. Anyway... after verifying that the fan was spinning and that the temp was fine, I drove it home cautiously, I noticed the coolant had gone down quite a bit below minimum when I got home so I chalked it up to that.

    Having said that, went out earlier today after topping up the coolant to maximum just to make sure everything was alright, took it on a short run (30 minutes) and no warning light until I pulled into my street... thought it might be that the coolant had went down but it was still exactly where I'd topped it up to. The only things I could think of where the coolant temp sensor, the thermostat or maybe the water pump?

    Does anyone have any suggestions? Not exactly the best way to start S2 ownership but it comes with the territory I guess

    Cheers

  • #2


    The coolant light comes on for two reasons. Low coolant (sensor in bottle) or coolant is too hot (sensor on engine).
    Next time it happens, with light still on, try disconnecting the coolant bottle sensor to see if goes out. If that doesn't work it's probably the coolant temp sensor which is faulty, or you are running hot.
    There are some good threads on testing coolant system on here. Search under the Forums tab.

    Was it the blue one in Aberdeenshire you bought? Looked nice on eBay
    Nothelle S2 Avant in restoration
    Wr Ur Quattro (also in restoration)

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    • #3
      Originally posted by Tractor Dave View Post


      The coolant light comes on for two reasons. Low coolant (sensor in bottle) or coolant is too hot (sensor on engine).
      Next time it happens, with light still on, try disconnecting the coolant bottle sensor to see if goes out. If that doesn't work it's probably the coolant temp sensor which is faulty, or you are running hot.
      There are some good threads on testing coolant system on here. Search under the Forums tab.

      Was it the blue one in Aberdeenshire you bought? Looked nice on eBay
      Thanks Tractor Dave, I'll try disconnecting the coolant bottle sensor, hopefully that's it

      Something I forgot to mention is that warm air isn't being pushed into the cabin for some reason, that to me would indicate thermostat or water pump

      It was the blue one in Aberdeen How did you know?

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      • #4
        They don't come up that often so it was a simple deduction

        Might be thermostat, water pump unlikely. It wouldn't go for two hours without it

        Are the two pipes entering the bulkhead getting warm? Could be the cable from the heater control has come undone or the matrix is blocked or has been blocked as it was leaking?
        What is the coolant looking like? Has it been serviced recently? Cambelt/water pump changed recently?
        Any sign of head gasket failure?
        Nothelle S2 Avant in restoration
        Wr Ur Quattro (also in restoration)

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        • #5
          Originally posted by Tractor Dave View Post
          They don't come up that often so it was a simple deduction

          Might be thermostat, water pump unlikely. It wouldn't go for two hours without it

          Are the two pipes entering the bulkhead getting warm? Could be the cable from the heater control has come undone or the matrix is blocked or has been blocked as it was leaking?
          What is the coolant looking like? Has it been serviced recently? Cambelt/water pump changed recently?
          Any sign of head gasket failure?
          Depending on what happens when I disconnect the coolant bottle sensor, I might take the thermostat out and test it to see if that's the issue. I agree it wouldn't go for two hours but the water pump could of suddenly failed when I got home, unlikely but knowing my luck...

          Not sure about the pipes entering the bulkhead, I'll need to double check. Not sure about the heater control either, the air is blowing but it's not warm.

          Coolant looks ok. Timing belt & water pump were done at 173,361 miles and it's not done many miles since.

          No signs of head gasket failure.

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          • #6
            This should help. AAN engine is very similar

            https://forums.quattroworld.com/s4s6/msgs/301760.phtml
            Nothelle S2 Avant in restoration
            Wr Ur Quattro (also in restoration)

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            • #7
              And your car has a Pembrokeshire registration. Probably sold new by Forge in Haverfordwest back in the day. They have long since gone.
              Nothelle S2 Avant in restoration
              Wr Ur Quattro (also in restoration)

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              • #8
                If the coolant level dropped i reckon you could just have air still in the circuit, especially if it only recently had the cambelt and water pump done. Run it up to temperature, turn the heater control to full heat, do you get heat? If not, sounds like it will need to be bled properly. Also, is the radiator getting hot too? Could be thermostat issue or installed backwards too.
                sigpic

                1992 3b S2 Coupe

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                • #9
                  Welcome!

                  The normal reason for beeping, if the coolant is topped up and the car is not hot, is the MFTS is faulty, this is the large sensor in the middle of the water rail. It’s a bit difficult to reach but you could try giving it a tap with a long extension, if this stops the beeping there’s your problem.

                  If the coolant level is dropping, put a sheet of cardboard under the car overnight to see if you can see where it’s dripping.
                  You’ll have to remove the undertray if there’s one fitted.

                  S2 Coupe 3B Project


                  Ur quattro restoration

                  S2 Avant

                  Boost is the new rock and roll!
                  sigpic

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                  • #10
                    There’s a bleed screw on one of the heater pipes where it goes through the bulkhead. It’s in the middle, just below the strut brace. Carefully undo it a couple of turns and top up till coolant comes out. Then you should have warm air.
                    The aircon button switches the rad fan on at low speed, even if the aircon is removed, quite handy

                    S2 Coupe 3B Project


                    Ur quattro restoration

                    S2 Avant

                    Boost is the new rock and roll!
                    sigpic

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                    • #11
                      Thanks for your input guys, I'm very grateful

                      Myself and a friend tried investigating the thermostat but we didn't realize you had to take the radiator out and unclip one of the power steering pipes

                      However, while we were doing this, the car was running and we noticed some very light smoke coming out of the exhaust so we killed it worrying that it might be the head gasket, we had a look at the coolant and there was a very light film on top so it's a little concerning. It's not black and is very faint but it doesn't smell of exhaust gases, the car was also fairly cold when started so it could be that. We had a look at the oil on the dipstick - normal, we had a look at the oil cap - normal, we even pulled the spark plugs to see if they were looking unusually clean but they were normal too.

                      Looking at the paperwork, it had the uprated (metal?) head gasket in 2010 P/n 034103383AD. Are these known for being weak also?
                      I think the film could be a result of the coolant passages not being cleaned properly after the previous HG. The coolant cap also seemed like it had Vaseline on it, perhaps a mechanic coated the cap's seal as it may have been leaking.

                      I've ordered a combustion leak test kit which should be here on Wednesday just to be on the safe side. If all looks good, I will run the car up to temperature and give the MFTS a tap with an extension then proceed with replacing the thermostat as the last documented change was in 2013.

                      My friend noticed that the top hose is perished and is leaking a little amount of coolant, after having a quick look at the options online, I've only been able to find silicone replacements, is there any OE style replacements out there?

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                      • #12
                        Best bet is the replace the coolant hoses, Roose do full kits and good quality. They are silicone but are the correctly lined versions and you can choose a load of colours or finishes, including a more oem look too from memory. Probably worth cleaning the full circuit with something, new hoses, refill the system and bleed it fully and go from there. The vaseline could just be down to the cap, they can have a click fit style and a normal screw on and sometimes are pretty difficult to open. I noticed a very small amount of filming in the header tank on mine when i started the tear down and a bit more at the base of the radiator but i dont think its anything too sinister to be honest, it had not been replaced in a good few years and the car was pulling cleanly, idle was smooth Temps in order oil pressure was stable and no consumption or loss of coolant, oil and underside of the cap showed nothing too. I have a metal gasket on and did also wonder about the health But may just do a compression test to be sure.

                        was it smoke or steam from the exhaust? Usually you can smell coolant being burnt off, its unmistakable. Always found the s2 creates a lot of exhaust vapour even when the ambient is not that low.
                        sigpic

                        1992 3b S2 Coupe

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                        • #13
                          Good news lads! Got the combustion kit today and the test came back negative for CO2 in coolant.

                          We tried bleeding the system and there were a few bubbles after which we took the car for a run while monitoring the gauges, all looked normal on both the coolant and oil temperature gauges. The warning light did come on again BUT it seems to be triggered by going up or down hills so I believe Tractor Dave was right about the coolant bottle sensor. Gonna try and bridge the sensor tomorrow to see if the issue reappears.

                          While I may have found the cause of the problem, I will still be changing the thermostat for piece of mind as it was last changed a while ago.

                          Thanks again for all your help, seems like a fantastic community!

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                          • #14
                            Originally posted by Scarecrow View Post
                            Good news lads! Got the combustion kit today and the test came back negative for CO2 in coolant.

                            We tried bleeding the system and there were a few bubbles after which we took the car for a run while monitoring the gauges, all looked normal on both the coolant and oil temperature gauges. The warning light did come on again BUT it seems to be triggered by going up or down hills so I believe Tractor Dave was right about the coolant bottle sensor. Gonna try and bridge the sensor tomorrow to see if the issue reappears.

                            While I may have found the cause of the problem, I will still be changing the thermostat for piece of mind as it was last changed a while ago.

                            Thanks again for all your help, seems like a fantastic community!
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                            The Perfectionist
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                            Audi Class Concours winner Stoner Park 2014, ADI Concours D'Elegance Class Winner 2008, Runner up 2014. Winner, S2Forum Show'n'Shine Billing 2006 & 2008.

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