Coolant leak solved

I had noticed over the past months that my coolant had been dropping by about 500ml over two weeks. I've not seen any evidence of red coolant leak in the usual places reported on this site, like at the plastic junction/temp sensor above the bell housing. And, until a few weekends ago, I had not smelled anything untoward going on under the bonnet.

Until, at my usual service I saw red coolant in the under pan and drip marks on the sump. The main fouling seemed to be at an inaccessible place under the fuel injector/pump on the left hand side of the engine. This discovery was preceded by a distinct foul smell of coolant coming from the hot engine for about a week.

There is a black metal pipe about 25mm diameter, running from the front of the engine from a flange in the body of the block, to the right and then backwards into a rubber hose into the firewall. Most of the fouling seemed to come from the place where the metal pipe joins the engine block, there's a flange and I suspect a leaking seal in there.

I grabbed hold of the pipe and rocked it to hear air being sucked in and coolant leaking out. Well, that's how I located the problem. To fix it I found this step-by-step procedure very helpful Link to Tdi Club website

There's nothing more I can add save to say this is a diy job and it's a satisfying one to do. Unlike the recommended procedure in the link, I didn't undo the rear turbo oil feed connection, and found that by removing all 3 hoses off the black metal pipe, I was able to manoeuvre the pipe and work on it without discomfort. I smeared some silicon sealant on the new o-ring, just for good measure. I must say that filling the coolant reservoir again took some patience.

While I was at this seal replacement job I replaced my thermostat, it's seal, and the flange seal. The car had done 128k miles.

A few pictures:

Here's a pic of the messy site of the leak, and

the end of the pipe when removed with the seal taken off, and

the old o-ring looked like this.

I hope this helps anyone else with similar trouble.