Hi everyone.

 

I’ve had a good google on this and have found more differnent answers than I expected!

 

The car is a 2016 2litre tdi dsg. There was no history with the car whatsoever, it looks like it’s stood for a very long time then been run - possibly  as a taxi - for 6 months or as long as they could get away with it untaxed. 

 

The above said, there are no underlying issues and it drives nicely now that the seized brakes have been overhauled!

 

immediately upon buying it I sent it to my regular garage to change everything. All oils, cambelt, water pump etc. the water pump was faulty so if was changed again. They were under pressure as the owner was going away and I suspect it wasn’t properly bled.

 

We noticed a few weeks later the sound of running water behind the dash. The sort of sound that makes you think a tap is running! I pulled the hoses off the heater matrix and gave it a good flush out with a hose. I reconnected it and fitted a new expansion tank as the old one was very brown inside. I cut the old one open, the silica bag was still in place and intact.

 

since then it’s been much better, but I can still - just - hear the water going round.

 

it looks like the bleed process is a bit drawn out. I’ve seen a video of a Audi using a pressure system to bleed it - I have one of those at home.

 

Ive also seen that you can use vcds to do a process too. I also have vcds

 

neither on their own mention the other and I don’t have enough specific knowledge on these cars!

 

if someone can point me in the direction of a definitive guide that would be very helpful

 

I’d quite like to drain it, run a bio flush through then refill but I may not need to do this as the new coolant is still clean 2000 miles or so later.

 

thanks for any help

Edited 17 November, 20241 yr by Pmedic
Spelling/typo

I’m leaning towards:

 

put bio flush in and drive to work.

 

use vcds to put car into bleed mode

 

drain as per Audi video.

 

fill as per Audi video.

 

run the bleed through using vcds.

 

does this seem logical?

 

thanks

 

My experience is with the Tsi. But the cooling system will have some commonality.

 

It's difficult to drain all the coolant out or a flushing agent in one go. Due to the multi chamber aspects of the system. When you pull the radiator hoses you only get about 5litres out of 10 or more.

 

If the cooling system had contamination it could be combustion gas, head gasket or oil, say oil to coolant cooler if it has one.

 

A vacuum filler will make it much quicker and more effective to fill but you can fill manually by holding the expansion tank above the engine and filling whilst the car is running. 

 

Cheers

 

it’s doesn’t overheat, pressurise, or lose coolant so deffo not a headgasket issue. 

oil cooler in the past is a possibility,

or it’s just been filled with plain water. It was a nasty colour when I first had the car.

 

Do the cabin heat controls work as expected - E.g. heat from both sides when called for? There can be an issue if the 'Mit Silicat' bag fitted in the coolant expansion tank breaks down and releases its contents into the cooling system, this can cause discolouration of coolant and blockages in the heating matrix.

Edited 18 November, 20241 yr by Warrior193
typo

Warrior they do now - the car and cabin both warm up quickly.

 

before it took ages.

 

i cut the old expansion bottle open, the silica bag was intact, so that too is - fortunately -eliminated.

 

i think all I need to do is run the purge process in vcds, but the “while I’m at it” part of me thinks for the sake of an hour or so’s work let’s get it perfect - it’s just how do I do that 😂

 

on all other cars I’ve owned it’s been bottom hose off and refill with the heater on - this is more involved 😂

20 hours ago, Pmedic said:

I’m leaning towards:

 

put bio flush in and drive to work.

 

use vcds to put car into bleed mode

 

drain as per Audi video.

 

fill as per Audi video.

 

run the bleed through using vcds.

 

does this seem logical?

 

thanks

 

Check very carefully that any flush product you use is compatible with aluminium. 

I was planning to use forte bio degreaser / coolant flush.

 

im not wedded to doing this

So, I think this is mission accomplished.

 

as suggested I put the forte treatment in then drove to the workshop.

 

i pulled the hoses off the rad and charge cooler and took a hose to them both. Quite a lot of crud came out of both and they both needed several minutes hosing before the water ran clear.

 

In then filled the system with water and remove the return line to the expansion tank. I ran it until this was clear too and then drained the system again from the bottom hoses.

 

time for a cup of tea.

 

now it was time to tackle the matrix. I bought an updated version from a local company who advertise on eBay. It’s a bit more money, but this is a job I want to do once only, and the wider waterways and brass/copper construction should last longer and prevent future problems. Also this came with the new seals and clamps.
 

Someone had clearly been in there before as some clips were broken and the annoying plastic cover from the videos was missing. Hey ho

 

This was the easiest and least time consuming part of the whole operation. The old unit came out easily, and the new one went in easily. Reconnecting the pipes is the hardest bit, helps to be left handed.

 

loads of crud came out of the old matrix, almost like sand. Whether it was the original and it had been flushed out is hard to say. It may well have cleaned out, but having gone this far I wasn’t chancing it.

 

then it was pipes back on and refill. I stupidly left my vacuum filler at home, So it had to be done the old fashioned way, and then bled using vcds. It’s definitely getting warm now.

 

i had to top it up when i got home but this is to be expected.

 

for future reference -

 

vacuum filing should speed the process considerably and enable more flushes in the same amount of time. I’ve not tried this yet, and hope to not need to now!
 

a smear of Vaseline on the male connectors greatly helps putting the pipes back on the radiators and the heater itself.

 

The documented difficulty in

getting all Of the old coolant out is no exaggeration. I wish I’d bought concentrated coolant as I’m now not sure there is quite enough antifreeze in. I did put a litre of concentrate in so it shoud be acceptable. I used g13 from euro, the new expansion bottle has got silica in it and to be honest for the £20 they cost it could/should be treated as a service item.

 

the whole process took about 4 hours, if doing again this could be reduced.