Spearos Posted January 3, 2014 Share Posted January 3, 2014 Hopefully someone can shed a little light on this little story... As well as my 90 I have limited access to SWMBO's 52 plate mk.4 Golf TDI 130, which we bought late summer 2013. On this the tandem pump was leaking, the leaked diesel finding its self onto a coolant hose. It was the pump cover that was leaking and stupidly you cannot get a gasket for the cover. So as the vehicle has done 130k I thought a new pump was the way to go... along with a new coolant hose as the diesel had deteriorated the old hose. Also, occasionally the temp gauge would 'act up' so for the sake of ~£20 I planned to replace the thermostat and temp sensor while I had the coolant drained - again the car had done 130k and there is no record of either being changed. So pump off, coolant drained, hose replaced, thermostat replaced, sensor replaced, new pump on. All going well. 2 litres of comma G30 poured in and topped up with the drained coolant after being passed through a piece of material to filter out any carp. Engine run up to temp with expansion cap off, no leaks, all once again looking good. Cap on, 3 mile test drive, check for leaks, level etc, all ok. Next morning I get into car, ignition on and I get 'STOP' 'LOW COOLANT' come up on the dash Check the coolant level... ok. hmmm.... Go for a little drive light stays on. I pull over, switch ignition off and check level... ok. Start engine and drive.... No light Since then the light has been on and off, the light mainly comes on when cold but not always. When it does come on if you switch ignition off and then back on the light doesn't come on :blink: I have done a 100+ mile trip to Milton Keynes plus numerous small trips in the 6 days since I carried out the work. So what the hell is going on??! Comma G30 meets the VW standard TL774 D/F for this car and therefore should mix with VW G12, which I presume is what the old coolant is. Ok, maybe I should have just premixed the new comma G30 50-50 with water and just used this but I didn't think it would matter? There is a sensor in the expansion tank which I guess is the trigger for the low coolant light. However this sensor was ok before so in my mind it seems a massive coincidence for it to fail whilst I carried out this work - besides, surely if it failed the light would be on constantly? So... Would the 2 litres of neat antifreeze added to the old coolant at say 50-50 (giving a high concentration overall) some how 'trick' the sensor resulting in the dash light? Or?... Please help! Edit: All parts used are genuine VW. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted January 3, 2014 Share Posted January 3, 2014 As things have contracted when cold the level is just too low, as it warms up things expand do level goes up enough to switch it off.Check the level when done cold and I bet it will be borderline low. Quote Link to comment Share on other sites More sharing options...
dirtydiesel Posted January 3, 2014 Share Posted January 3, 2014 The level sensor is the one in the header tank, it in no way looks at coolant concentration. It is not unusual for the level sensor to fail as you describe after the coolant has been drained, a new genuine header tank are less than £20 though, and they do tend to craze and crack as they get older. Quote Link to comment Share on other sites More sharing options...
Spearos Posted January 3, 2014 Author Share Posted January 3, 2014 As things have contacted when cold the level is just too low, as it warms up things expand do level goes up enough to switch it off. Check the level when done cold and I bet it will be borderline low. With the level of coolant in tank being the first, and most obvious thing to check I have checked it several times over the last week. However I will give the level a thorough examination first thing tomorrow morning! The level sensor is the one in the header tank, it in no way looks at coolant concentration. It is not unusual for the level sensor to fail as you describe after the coolant has been drained, a new genuine header tank are less than £20 though, and they do tend to craze and crack as they get older. Thank you for confirming that the sensor doesn't give a toss about the concentration Dan. That's one 'possibility' dismissed! And I have heard that these sensors fail quite regularly, so with the wisdom of your experience I think a new tank is probably the way to go... first!.. Quote Link to comment Share on other sites More sharing options...
Jon White Posted January 3, 2014 Share Posted January 3, 2014 I have no idea what the correct procedure is for a golf, but to me it sounds like you may not have completely bled all the air out of the cooling system and have an air lock somewhere. Did you possibly miss a bleed screw or something? Jon Quote Link to comment Share on other sites More sharing options...
M.I.B Posted January 3, 2014 Share Posted January 3, 2014 There is no bleed screw - this is a typical sensor failure. Buy a new coolant tank. Sensor checks the level, not the constituents of the fluid so you can have it full of beer - it dopesn't care as long as it is full. Don't forget that 100% and anti-freeze mixture will freezebefore a 50/50 mix. I can't remember why, I did learn why a long time ago in advanced chemistry, but have since forgotten, because I just know that it does. Quote Link to comment Share on other sites More sharing options...
matt bristol Posted January 3, 2014 Share Posted January 3, 2014 I had a Seat Leon which had a similar issue, the sensor in the expansion tank is pants on these (both VAG vehciles). If the coolant is visually OK then i would say you are all good to go. FYI I cured mine by... well I'm not sure to be honest it just stopped playing up after a while. Quote Link to comment Share on other sites More sharing options...
Spearos Posted January 3, 2014 Author Share Posted January 3, 2014 Brilliant! Thank you so much guys I can now order a new header tank being very confident that it will fix this problem, and not be a shot in the dark... and of course waste of money. Yet again this forum has 'done the business' - the depth and variety of knowledge on here is second to none IMO, that's why I have no hesitation being a supporting member. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.