A4 2.4 V6 overheating

[Harris]

Hi again

ive changed the radiator on my V6 after putting up with a slight leak for the past year. 
 

works fine, well the radiator does but now the car overheated and the low coolant level light comes on despite there being no sign of leakage.  My first thought was that the thermostat has failed in the shut position but after discovering that changing that would require a cam belt change I was hoping it was something else

Any ideas welcomed 

[Steve Q]

I'd be first considering air in the coolant system. 

[Magnet]

Hello Harris,

We need to clarify some facts before moving on:-

 Any degree of overheating prior to renewing the radiator - even moving slightly above the normal 90? 

‘Low level light comes on even though no sign of leakage’. When the low level light comes on, is the coolant level actually low or not? 

Did you fully bleed the system (with heater set on max. temperature) after you fitted the new radiator? 

Where did you get your new radiator from? 

Kind regards,

Gareth. 

[Harris]

Is there any way to bleed air out of the system other than topping up the water tank?

the car didn’t overheat prior to me swapping the radiator. It had been loosing coolant more and more since last July and I was at the point I had to top it up every time I got in it. The old rad was rusted out all over and leaked from most of the vanes. 
 

I changed it with a brand new radiator from euro car parts as Audi didn’t have one in stock and with lock down had to order from the factory 

I only drained water from the rad bottom bleed screw before I removed it- as the rad was so blown not much more came out- the heater control in the car was set to 22 but turned off before shutting down the engine the last time I drove it as I knew I was going to remove the air con rad  I have not taken it to be regarded as it’s now over heating

since I changed the rad I noticed the car got to temp fine but would then creep past 80 ( normal running temp) to the next marker on the gauge (halfway between the middle and red) at that point the low coolant level flashes up. I waited for about ten mins before opening the water bottle but it was still under pressure and most of the water in the tank came out so topped it up and refilled drove it again and it over heaters 

any advice guys would be great
 

 

[Magnet]

Thanks for the important additional information Harris. 

Within reasonable limits, the bulk of the trapped air should expel itself over a couple of days, so great volumes of trapped air in your case, should not really account for your ‘new’ overheating issue. 

My procedure for draining/ replacing coolant is to always ensure the heater control remains set on max. before draining and when filling. 

Back to your overheating, where you didn’t have overheating before:- The only component you have changed is the radiator, so logic points to that component being the suspect, if correctly fitted. Yes, I know it’s new, but it can be surprising how many new parts made east of the Thames estuary, can be substandard, out of the box. I would not assume new equals serviceable any more.

Kind regards,

Gareth.