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Losing Coolant when AC is on

Discussion in 'Ibiza Mk5' started by mac132, Jul 7, 2019.

  1. mac132

    mac132 Active Member

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    Hi

    I've noticed I'm losing coolant, but only when AC is on in my 2009 1.4 Ibiza. Coolant level was just under max, after running AC levels have dropped under minimum. This only happens when AC running.

    Any thoughts what could be the cause?
     
    #1 mac132, Jul 7, 2019
    Last edited: Jul 7, 2019
  2. RUM4MO

    RUM4MO Active Member

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    This is quite illogical, drive wise, the auxiliary belt that gets driven from the crank shaft, drives the alternator and the AC compressor - maybe check inside the cam belt cover to see if the water pump is leaking.

    Water will be seen to "escape" when the AC is running or after it has been running, but that is just condensate ie water that has been stripped out of the ambient air - and not from the engine coolant system.
     
  3. everson38

    everson38 Active Member

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    How did you get on in end?

    Sent from my SM-G900F using Tapatalk
     
  4. Crossthreaded

    Crossthreaded Active Member

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    Yup, "does not compute" was my initial reaction. Then I was thinking, "drops from Max to under Min" - that's a lot of coolant! It must be going somewhere and that amount will leave witness marks. Then I was thinking could it be an over temperature problem (engine has to work harder when driving the compressor and a/c is usually being used when ambient is high anyway) causing coolant to be ejected due to excess expansion? Maybe unlikely because it would probably do it in, for instance, heavy traffic on hot days without a/c in use? but could be a "sticky" thermostat or partially blocked rad?
    I like your suggestion to check the water pump. They can leak in unexpected ways (ie only when cold - only when hot - only when idling - only when running at speed - etc. In other words just because it's not actually dripping when you look at it doesn't mean it's not leaking.) Look for witness marks which will be coloured so reddish chalky deposit, blueish chalky deposit or to put it another way, if it's condensate it'll be clear.
    I've run out of ideas just now and better half want's a lift to the shops. Do let us know what it turns out to be won't you? You never know, one of us may run into the same problem.
     
  5. AlR

    AlR Active Member

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    Hi there, more info is needed. Has there been any work done on the car which may have opened the cooling system? Does the level come back up if AC is off? Could it be that the heater matrix is leaking & you only notice the level going down as you've turned the temperature up as AC on is too cold but you need the demist? The heater uses the waste heat in the engine coolant to warm-up the interior airsupply. If you have got the temperature setting low, it will not be allowing coolant flow through the matrix, so maybe it will lose the coolant but you won't see it under the bonnet until you open the heater valve and then the coolant gets pumped into it to replace the lost fluid resulting in a level drop.
     
  6. RUM4MO

    RUM4MO Active Member

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    I think that some of that is wrong, as far as I know, all cabin air temperature is carried out by using "air blending" so there is no coolant control valve regulating the flow of coolant through the heater matrix, just full flow and a damper plate that allows 100% of incoming air to pass through the matrix or and little as 10%, maybe even 0% but I'd not think that that as possible. The rest of the incoming air is bypassing the heater matrix zone and probably passing through the chiller evaporator, which if the chiller is disabled will mean that it is just incoming air unconditioned that is blended in or mixed with the heated air.
     
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  7. AlR

    AlR Active Member

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    @RUM4MO what you say is entirely likely - I was basing my comment on "traditional" or historic interior heating controls. I still think it will be engine temp related rather than AC operation, but still need more from the OP.
     
  8. RUM4MO

    RUM4MO Active Member

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    Air blend as a means of controlling cabin temperature might have been rolled out by Ford Europe back in 1970ish and quickly taken up as being the best way to control cabin temperatures by most manufactures even VW after they added water cooled engines to their range.
     
  9. Crossthreaded

    Crossthreaded Active Member

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    I think this is right. In days of old (yawn!) there were heaters which controlled the temperature by restricting the flow of water through the heater matrix if you wanted less heat - that was why the old Mini had a bypass hose. (and they were a right little pig to change - anyone remember them?) If the engine is cold and the main thermostat is closed you need a way for the water to still be able to circulate. Now a days all the manufacturers that I have come across accomplish this by allowing coolant to circulate through the heater matrix at all times. So when the engine is up to normal running temperature (just below boiling point, say 90 degC for most) temperature inside the car is varied by a flap which allows cool air from outside the car to be admitted or, if you move the control (manual systems) the air is routed through the matrix and picks up heat. The engine's coolant circulating through the matrix at all times. In fact this is a much better way of doing it, I remember it was a really common job to renew the water control valve on these older systems. There were several different designs but they all leaked in time.
     
  10. RUM4MO

    RUM4MO Active Member

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    Mind you, I could shoot myself in the foot here as Ford Transits and Fiestas did revisit that "lets try a water valve" for a while - that kept a few people in a good living making, selling, replacing these valves - why oh why try to fail when there are other ways of doing this.
     
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  11. Crossthreaded

    Crossthreaded Active Member

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    Aye, wasn't so bad doing the ones where the valve was mounted on the engine but a rotten job to do where some "clever ****" of a designer decided it would be just the thing to put it inside the car on the inlet to the heater matrix. Of course once you had a leaky valve inside the car you needed to supply the driver with welly boots and, for people like me, a chamois leather to dry the condensation from the lenses in your specs!
     

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