A4 1.9Tdi Coolant issue?

[Mike1996]

Hi, I don’t know if it’s just me being paranoid or it’s the beginning of an issue. Lately I’ve noticed my coolant level on the expansion tank is sitting on the min mark, after driving for a couple of hours I check again and noticed it’s just below the min mark now? About 1/4 inch. Coming out the next morning it seems to have raised back up to it’s original mark. Is this normal? One job I know needs doing is thermostat needs replacing as the car never gets about 70 unless sitting at idle.
Just looking for piece of mind to stop my mind from making me paranoid

 

[Mike1996]

Was just out looking at the car, saw some rainbowish type fluid on the ground guessing it’s coolant? So possibly a leaking pipe maybe?

 

[Charlie Farley]

Very straight forward reply chap really.
whatever your coolant level is when cold is the level, allowing for expansion when hot so it will be a higher level .
Ideally it should be midway when cold allowing for expansion it should not really go over the max mark .
If you top it up when cold to midway and run it for a day or so and see what occurs, if it goes down when the engine is cold then you have a leak.
these plastic header tanks do have a habit of splitting in different places and its not always that obvious at first, mostly just below the water inlet, maybe check yours is dry.
If it is and yours is still going down you have a leak without doubt, just a matter of tracking it down.

 

[Charlie Farley]

Temp wise , you may have a failing thermostat or possibly an air lock in the system , most times it is the thermostat that plays up on temp issues.

 

[Mike1996]

Very straight forward reply chap really.
whatever your coolant level is when cold is the level, allowing for expansion when hot so it will be a higher level .
Ideally it should be midway when cold allowing for expansion it should not really go over the max mark .
If you top it up when cold to midway and run it for a day or so and see what occurs, if it goes down when the engine is cold then you have a leak.
these plastic header tanks do have a habit of splitting in different places and its not always that obvious at first, mostly just below the water inlet, maybe check yours is dry.
If it is and yours is still going down you have a leak without doubt, just a matter of tracking it down.

Thanks for the reply mate, the thermostat is definitely at fault as temp never reaches optimum temp. If there is a leak somewhere I can’t understand why when I remove the cap for the tank the coolant rises a lot, pretty much at max level. Either it must be a tiny leak or I’m deluded lol but I’ll have a proper look tomorrow when I can actually see outside

 

[Charlie Farley]

are you getting hot air in the cabin when the heater is on high?
The temp senders are also a known issue, they can give erratic readings.

 

[Mike1996]

are you getting hot air in the cabin when the heater is on high?
The temp senders are also a known issue, they can give erratic readings.

It comes out warm, but it’s strange if I let the car get to operating temp it comes out cold? It’s very strange. So 90% of the time it’s nice and warm but noticed the other day sitting in a drive-thru it got to 90 but heaters got cold

 

[Charlie Farley]

You could very possibly have an air lock in the heater matrix as that the highest point in the system and so many guys have encountered the same problem.
engine never really gets to temp, heater is cold or warm or randomly both etc, water level fluctuates in the header tank.
the system is effectively pressurised , when you have an airlock the system is not circluting fully , so if you remove the header tank cap the pressure flows back .

before rushing into a thermostat replacement , loosen clamp on the heater matrix an see if water comes out when running.

 

[Charlie Farley]

your stat is not totally shot as you are getting up to temp when idling , but it may be on the way out.
check for air locks first as that will be free , then go from there.

 

[Mike1996]

your stat is not totally shot as you are getting up to temp when idling , but it may be on the way out.
check for air locks first as that will be free , then go from there.

Ok mate I’ll give it ago, where exactly is the heater matrix?

 

[Charlie Farley]

middle of the bulkhead , you'll see two hoses disappearing through the bulkhead one in flow in and the other out, don't recall which is out but just try one then the other, as long as you get coolant flowing through it unhindered thats the object.

ideally when the car is up to to temp the gauge should sit spot on 90 and when you wack on the heater to full or close to full temp setting it should be really hot air .

 

[Mike1996]

middle of the bulkhead , you'll see two hoses disappearing through the bulkhead one in flow in and the other out, don't recall which is out but just try one then the other, as long as you get coolant flowing through it unhindered thats the object.

ideally when the car is up to to temp the gauge should sit spot on 90 and when you wack on the heater to full or close to full temp setting it should be really hot air .

I think you’re right mate, I didn’t end up removing it, but the bottom one is warm top one is ice cold so I’m guessing it’s blocked

 

[Charlie Farley]

Give it a go chap, like i say , it's free and free fixes are always the best to start with.
if not its one item less to check .