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Ross
Ross , Diagnostic and repair technician
Category: UK Car
Satisfied Customers: 1158
Experience:  Licensed diagnostic and repair technician
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Audi A2: I have an Audi A2, which has been showing coolant

Resolved Question:

I have an Audi A2, which has been showing coolant fluid issues. We replaced the engine temperature sensor and overflow bottle (with sensor), but it still seems to loose fluid. No visible signs of leaks anywhere, although it looks like the bottle (brand new) spits out excess fluid cause there is a little on the rim of the bottle in the middle.
Temperature gauge on the dashboard never goes above 90 degrees, although coolant warning light (with really annoying 3x beep) comes on regularly for short periods before turning off again. On long journeys (300 miles +) there are no issues, in town it is a constant on - off of the coolant warning. I can keep topping it up with water / coolant but that can't really be the answer.
When the engine is cold there is still a lot of pressure in the system, because the coolant level is really low, and when I unscrew the cap on the expansion bottle it makes lots of hissing noise and spits out through the overflow.
I'm confused as to how the system is supposed to work.
Any tips ?
Submitted: 3 years ago.
Category: UK Car
Expert:  Ross replied 3 years ago.

techmachine :

Hi, welcome to Just answer! My name is XXXXX XXXXX i will help with your question

techmachine :

Does your cabin heater blow hot air as normal or do you find its a bit cooler than usual?

Customer:

The cabin heater works normally. It blows coldish (not properly air conditioned but cooler than outside temperature) when dail in on blue, and warm air when on red. Nothing abnormal there.

techmachine :

Ok its possible the water pump is failing, it seems to be quite a common problem on these engines now where the pump impeller comes loose on the shaft so that's a possibility, If you get the level topped up correctly and start the engine with the cap off, you should see the water circulating, if you get some one to increase the RPM you should see water flowing in the bottle, if its not, its probably the pump. Otherwise the first part to change here would be the thermostat, it sounds like it might be sticking closed, enough to overheat and pressurise around town but keep cool long long runs with a good air flow

Customer:

Thanks, XXXXX XXXXX check that.

Customer:

Hi Ross,

Customer:

Checked, and the water / coolant flows fine when revving.

Customer:

Would the thermostat sticking account for the loss of fluid ?

techmachine :

Yes it certainly would, the thermostat will cause the temperature to increase, although it wont over heat necessarily it will cause excessive pressure, the lid on the coolant bottle has a pressure release valve so when the pressure gets to a certain point it will let the steam out, it wont take long for the level to drop.

It might be a good idea to get the car into some one with an emissions tester first though because loss of coolant could well be due to a failing head gasket, its not something I would be to worried about at this point but its cheaper in the long run to get this diagnosed correctly. An emissions tester can do a "sniff test" or there is a block test you can do, both do the same thing, they check for exhaust gasses in the coolant. I have known the heads to warp and/or gaskets to fail unfortunately which lets the coolant into the cylinders where its burnt with the fuel. If there is a lot of white gunk on the underside of the oil filler cap or on the dip stick its highly likely its the head gasket, in which case I would recommend a compression test is done and although a thermostat is not all that expensive, half an hour doing a compression test and sniff test will tell you a lot more about what's really going on which ultimately will keep the costs down.

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