Vz v6 wagon towing issues

[b3h3m07h]

The other day a friend of mine went to go pick up a caravan from down south but ran into a few issues, the car started to overheat. It has a transcooler fitted and has always been serviced by the dealer. Before this overheat it happened once before because who ever worked on the car and resprayed the front end disconnected the thermo fans and didn't plug them back in.

So currently the car by itself won't over heat but doesn't appear to be sucking coolant back in from the overflow. The system has been bled correctly and has even been taken to a dealership where they supposably fixed the problem, they said the radiator was blocked by 10% and that they tested it with their heaviest trailer and it didn't overheat, hook the caravan up and it overheats. They also said they did a pressure check on the cooling system and a check for exhaust gases and no issues there.

I have noticed though that when I switch the car on and the coolant starts to warm up a steady flow of bubbles will continue to come out of the filing point of the cooling system.

What should I try next or can anyone recommend a good workshop we can take the to to have the problem diagnosed correctly? My mate lives on the south side of adelaide.

Cheers

[RiCeY]

If bubbles are coming out it hasnt been bled properly. Is there a plastic screw near the top of the radiator, drivers side facing the engine? If so this is to bleed the air out of the radiator.

Also if coolant isnt being drawn out of the overflow it could be a failed cap, fit a new one to be safe.