Lol, thanks DennisG01

Rich, I'm curious, in your final re-sealing, did you discover anything that would indicate why it was leaking?

I had a big leak after I replaced mine, but it was 100% my fault. When reinstalling the new upper radiator hose, I did not correctly seat the clip that holds the hose to the thermostat housing. I was driving it and steam started coming out from under the hood. Luckily I was close to parking lots and could quickly pull over. Coolant spewed all over the front of the motor. After cooling off, it took me probably 10 seconds to fix my screw up.

Nope, never found anything that caused it to leak and its STILL FREAKING SLIGHTLY LEAKING :wall:. Woke up this morning to the "add/top off coolant," error message. Topped it off drove from Staten Island to Manhattan, to the Bronx and finally to Brooklyn. So far no new message and I didn't get a chance to check the fluid tonight. I'll check it in the morning. I'm tired and don't want to be bothered with it at the moment..

Hose is seated fine, now I'm convinced that it's just messing with me. If this would've kept happening when I was younger, not only would I have a leak but, I'd probably need a windshield and headlight by now also. I've matured, this too shall be figured out. What I did notice was, the new housing bolts didn't fit as well as the old bolts, they seemed as if they were going to snap before the housing even reached the block so, I reused an old bolt for the top of the housing but, I had to use a new bolt for the bottom. Now I have to wonder if the bottom bolt is doing the same thing and if I should change the bottom bolt as well? I can't reuse the old bolt though, the head was rounded.

I noticed the same issue with the bolts, so here is my theory. Perhaps MB used thread locker from the factory and that is jamming the threads? Something like that happened to me once before. So, when I reinstalled T-stat I actually cleaned/re-threaded the holes to make sure new bolts go in OK. Otherwise, it would take much more than 25Nm to tighten them and I was worried about stripping the threads.

BTW, got a similar message couple of days ago due to falling temperatures, so it might be OK for you. It's also possible that you had a bit of air in the system. See if the message comes back.

I thought it was just me with these bolts, glad/sucks to hear that there may be an issue with MBs replacement bolts, for some of us. Started the truck this morning, no top off/low coolant message, drove to work and still no message . I should have checked the actual level but, it was freezing so I just jumped into the truck this morning. I will check the level around noon-ish.

Update: Just checked the coolant level and it's fine AND there's no sign of any leaks... :nix:

Hang on a sec. When you say it's leaking, do you just mean that you're getting the top-up message? Or are you seeing coolant on the floor, on the side of the motor?

If it's the former, it could easily just be that the air needed to be purged. The way that system is designed, it has to move in and out of the coolant tank, meaning it has to thermally cycle.

Tap and die sets are cheap nowadays, and this is a good reminder to fetch myself a metric set.

Actually you hit it right on the head. The message popped up and I had to top it off but, I never seen any coolant now that I think about it. Lol, :smash:
.. I've realized that you have to be able to laugh at yourself when you realize certain things after the fact😂😂
I know that I read that there is no special way to bleed this system, my bad.

Better to have and not need it, then to need it and not have it.

All's well that ends well, brah. :y

Again, I thank each and everyone of you...
Those in the midwest and those that are caught up in this wicked weather, be careful tonight and tomorrow.