Hi wondering if anyone can help,, I have a MK3 2018 1.6 TDI Octavia and over last 8 months have had 2 new heater matrix several flushes,, new coolant pump, replaced a pipe from matrix to drivers side as I am getting cool air from drivers side vent.

 

I am for some reason able to open coolant reservoir even when engines are full temp and there is no pressure, no leaks no loss of fluid.

 

Car isn't overheating, the immediate right air vent drivers side cooler than all the rest.

 

Sometimes middle vent to drivers side is cooler but after idling a while seems to get warmer.

 

It has been driving me crazy in and out of garage 5/6 times now.

That sounds like two potential faults. Water pump failing and potentially the flap motor either failing or needs recalibration. Do you have a code scan of the car?

Hello and welcome 

 

Have you had the car scanned for fault codes?

 

Have you tried resetting the HVAC vent flaps?:

 

 

With regard to no pressure in the cooling system, has the seal on the expansion tank lid failed?

 

Gaz

 

Hi thanks for the reply,, it was a new reservoir tank fitted when 1st matrix got changed due to silica bag or whatever and yes I have ran the reset flap thing numerous times.

Did the expansion tank come with a new lid as well?

 

Asking the obvious just to cover the bases.

 

Gaz

The garage has apparently checked for fault codes and nothing came up....I'm meant to put back into them Thursday so they can check air temp flaps or something, and replace coolant reservoir cap but I'm reluctant as it's just more money and might not solve issue

I believe coolant reservoir was complete with lid when replaced 

Water pump and timing belt were changed November last year, The garage has apparently checked for fault codes and nothing came up....I'm meant to put back into them Thursday so they can check air temp flaps or something, and replace coolant reservoir cap but I'm reluctant as it's just more money and might not solve issue

1 minute ago, Craiga0406 said:

The garage has apparently checked for fault codes and nothing came up...

 

Do you know what they were scanning diagnostic codes with?  Some generic code readers don't capture all relevant fault codes.

 

If it wasn't a VAG related diagnostic tool, maybe get someone with VCDS to have a look for you:

 

 

Gaz

Oh right I will ask the question, but he did say this morning he can apparently control the flaps from the computer they use so I guess it's correct....it's a mainstream garage as apposed to sole trader I go to

No leaks but no pressure seems to suggest to me that any pressure leak is likely to be happening above the coolant water line, otherwise you'd surely see liquid.  Hence suspecting the header tank's lid seal.

 

Being able to control the flaps would indicate it's not a generic code reader being used. 

 

Gaz

I guess I will have to wait and see what Thursday brings .....

 

Water pump and timing belt were changed November last year, The garage has apparently checked for fault codes and nothing came up....I'm meant to put back into them Thursday so they can check air temp flaps or something, and replace coolant reservoir cap but I'm reluctant as it's just more money and might not solve issue