Hi guys,
I have enjoyed this forum for couple of my projects, so I would like to share mine since I could not find it here. I got stranded in NYC due to a coolant leak /overheating and had to ship the car to Michigan where I live and take a one way rental. I got the car back today and dived into it right away.
At first glance this job looks like you will have to tear down the whole dash, but don't freak out like me. This is not the case.

Time: Less than one hour if you can extract the broken part in one piece
Tools: Basic hand tools/sockets plus extra long pilers

The part in question is A1669970659 / A1669971459. You can find some used ones on ebay, otherwise for a new ones dealer only. The hose that attaches to it is A1668304096, which is the first part number you will see to figure what part you need.

Process:
1. Remove large engine cover (just pull it up, snaps in place)
2. Remove plastic cover on driver side by the windshield that covers brake booster. Push it towards the windshield and pull up on the other size. It seats there pretty loose.
3. Remove the water drain pipe
4. Remove the engine compartment rubber seal (driver side part only). Just pull it in the middle and then keep pulling towards the end of the driver side
5. Remove plastic firewall cover (upper middle piece) by unscrewing two screws (8mm) and pulling it out. You will have to wiggle a bit to get it out. Now you should have pretty clear access to the clamps.
6. Remove/release pressure from the clamp firewall side using one hand and extra long pliers and pull the broken tube out first then the clamp. I recommend replacing the clamps at the same time.
7. Remove/release pressure from the clamp engine side and extract the broken part. IMPORTANT: Be really careful, if you break that piece in more pieces, they will go deeper inside that hose and let me tell you, getting these pieces out is no fun, which is what I had to do. I spent about 45 minutes shaking that hose and pushing it down to get all the pieces out and I am not still 100% sure all of it is out. I wish I knew which way the coolant flows there. If out of engine, you possibly can run some fluid out from there with the pieces while running the engine (watch the temp gauge and turn off the engine if it gets too hot!)

The installation is reversal to removal. I am waiting on my part and I will update this post once I get this done.
If any one can chip in and tell which way the coolant flows from the engine side it would be great. Also if out of the engine, at what temperature it should start flowing? I had the engine running for couple of minutes up to 80F on the temp gauge but no fluid came out.

Here is some pictures I took from the process:

Part in question is No. 20 (NOTE: If you have GL550 like I do, you will not have that other connection - I believe that is only on the diesel European engines, which this diagram is of)


Here is how it looks broken:



Removed brake booster cover and the drain connector pipe



Removed engine compartment rubber seal


Removed plastic firewall cover (upper middle piece) by unscrewing two screws (8mm) and pulling it out




Exposed part to be removed


Pliers used



Broken part out