Coolant Loss

[Pompey_Pip]

When on the motorway the other day, I had a warning come up saying coolant low, stop engine and check level (or words to that effect).
So I stopped at a Shell garage, and the coolant was low, so bought some long life coolant and topped up.
The car is 2 and a half years old, with 13,000 miles, I never checked the level, and the car was serviced 1 year ago (due on the 18th June).
I had my last S3 for 8 years, and never had to top up the coolant.
I have been checking the coolant for the last three days, and there seems to be no discernable loss.
The manual says that coolant loss is not expected, and to take it to the dealer if you experience it.
Has anybody else experienced slow loss, I don't want to pay the dealer to investigate a very slow loss, as they probably won't find anything.
I'm thinking of sitting on it and monitor to make sure it doesn't get worse.
What do other people think?

 

[vatdim]

It could be a lot of things. Knowing that the water pump / thermostat assembly is a weak point of these engines, I would start my inspection there. As you pointed out, however, slow loss is difficult to trace, unless you perform a pressure test.

 

[Pompey_Pip]

It could be a lot of things. Knowing that the water pump / thermostat assembly is a weak point of these engines, I would start my inspection there. As you pointed out, however, slow loss is difficult to trace, unless you perform a pressure test.

But would a pressure test tell you where the leak is? It would confirm there is a leak (which the loss of coolant is evidence of anyway), but how could it be used to tell you where the leak is?

 

[vatdim]

But would a pressure test tell you where the leak is? It would confirm there is a leak (which the loss of coolant is evidence of anyway), but how could it be used to tell you where the leak is?

It wouldn't tell you where the leak is directly, but can offer more clues, for instance, if the leak is somewhere on top, you or a mechanic should be able to spot the coolant spraying out of the system. Keep in mind that all leaks will eventually leak downwards. Thus, a cardboard placed under the engine bay might be able to point you toward the whereabouts of your leak. You could also use one of those coolant dyes that are added to your system, and once it is pressurized, you then use a UV light in order to find the exact location of the leak.

 

[monkeyhanger]

Or it could be just a long term airlock in the system from filling that's finally freed itself, if it doesn't recur. I'd keep some coolant with the car at all times in case you need it, and monitor.

 

[Pompey_Pip]

Or it could be just a long term airlock in the system from filling that's finally freed itself, if it doesn't recur. I'd keep some coolant with the car at all times in case you need it, and monitor.

Sat in a lot of traffic in the heat yesterday, so I guess the cooling system was being used to the max, just checked and no loss, so fingers crossed it was just one of those things.
Cheers to all for your advice.

 

[Sparks43]

Sat in a lot of traffic in the heat yesterday, so I guess the cooling system was being used to the max, just checked and no loss, so fingers crossed it was just one of those things.
Cheers to all for your advice.

I had this in my 8V S3 which was a known issue with Thermostats etc and topped it up but it also went in and they pressure tested and found nothing - Never did it again in the time I had it - They said could have been Airlock although like you the car was nearly 2 years old then

2 and half years old it's under warranty, so if you're concerned get it booked in at least it's then logged on their systems that this occurred within the warranty period

 

[Kevmoz]

I had something similar in my Golf R where the level dropped to the min. Kept an eye on it and all appeared good but noticed some water marks down the front the engine. Booked it for a service and the tech said the water pump/ housing was leaking and changed under warranty. Just mention it when you book for your service as a new pump/ housing took a few days to arrive with the dealer.