GL450 coolant hose leak update, problem identified!
The Best of Mercedes & AMG
Got the replacement done today. Did take about 5 hrs plus a a second trip back to the dealership for an additional hose I broke and a trip to Home Depot.
1. Be very careful removing the third hose that attaches to the passenger side turbo coolant hose. I was super gentle and the plastic fitting still broke. Luckily the passenger side turbo coolant hose is very accessible and easily to replace. Nothing like the driver side. But it did require buying the fourth hose at +$80.
2. The one hose that attached to the center of the engine (I believe) has a plastic fitting that goes into the metal. When trying to remove it the plastic fitting broke off and was stuck inside. Tried to pry it out with every pick tool possible but no luck. Finally got it out by screwing a screw from home depot the same size as the plastic. Screwed it in and then pulled out the screw and plastic fitting. This required a trip to Home Depot.
Every coolant hose I touched (all 4) broke at the plastic sections. There was also visible deterioration on the inside of the plastic. It’s pretty sad they used such a crap plastic. My gl550 only has 38k which is pretty bad for these all to be cracking. Parts guy was not surprised as all and they were fully stocked with these parts.
$350 in parts and 5+hrs and my leak is fixed. All parts are replaced with the same cheap plastic that will likely fail again at some point. At least it’s good for now.
I went from the front with a 12inch 3/8 ratchet to get the bolt off. It was pretty easy except being extremely hard to see. 8M. Getting the 2 hose fitting’s out was a Pain. Use a pry bar to put outward pressure while rotating the hoses up and down. It eventually comes out. Top line first and then bottom line. Top line is way easier. Bottom line took me some time. Be careful what your pry bar is pushing off.
I was hoping it would be an easy job once the air inlet pipe is removed but looks like a major PITA.
I was hoping it would be an easy job once the air inlet pipe is removed but looks like a major PITA.

Since it's the upper plastic part is broken, I'll probably remove the good piece from the new part and make my own part without messing with the lower bolt.
This is the view from the driver side.



