So... driving to meet some friends for breakfast (about 30 mins away- mixed highway/street driving). I parked the car in a parking spot, started walking to the restaurant, and i noticed a smell- turned around and saw my car was DUMPING coolant on the ground. I opened up the hood and noticed coolant leaking out of a hose where one of the clamps has failed (not broken, just not tight enough?) So long story short... my friend drove me to AutoZone- I bought an adjustable clamp, the recommended coolant and repaired it in the parking lot. Drove straight to the mercedes mechanic I use here in Orlando, FL to have him sign off on my repair. Has anyone else had this issue of those clamps failing?

 

Which year model?

 

2015 SL550. 40K miles.

 

I too had a coolant hose clamp fail. I got a replacement clamp from MB and topped up the coolant.

 

That's crazy! Same hose? Did it happen while you were parked or driving? What year SL550 do you have?

 

Took a look at my 2018 550 and interesting to see that the hose clamps MB using are same type now being used to install PEX hose in home plumbing (install/crimp and forget).

If in fact this assumption is correct there is no room for install error and no concern for rubber aging that might cause a leak.

Be good to hear from KeithS (OP) and Kleon who have had leaks to let us know what their MB tech had to say.

 

Hey Steve. My MB tech (not at mercedes dealer), gave me the thumbs up on the adjustable clamp. Didn't have anything good or bad to say about the clamp that failed. I'm getting a second opinion on the clamp at a different MB repair shop soon- i'm getting a 4 wheel alignment (just ordered new Michelin super sport tires) so I'll let you know what they have to say.

 

You are lucky this did not happen while you were on the road. I had to buy a new engine for a 1997 BMW 740i even though I was still barely under an extended 100,000 mile warranty. It's an ugly story that led me from a BMW super enthusiast to Mercedes. That era BMWs with V8 engines were notorious for failure of the top hose connection on the plastic radiator. I even had purchased a radiator, stored in my Utah garage. Driving over 11,990 ft Loveland pass in Colorado on my way to instruct at a BMW Club driving school, I saw coolant streaming over the hood. I knew what had happened. I was able to reattach the radiator hose and top off with water, but I left the cap off the radiator so that pressure would not build up and blow off the hose. I was pretty much able to coast all the way into Denver, only occasionally starting the engine and ensuring that the temperature gauge never went into the red. Unfortunately, just a few miles from the Dealer, I had a warning "Loss of Oil Pressure - Stop Engine" so I stopped and had the car towed to the dealer. The dealer did some checking, replaced the radiator and sent me on my way home to Utah in a convoy with my wife in another BMW (540i M Sport, 5 speed manual.)

Two hundred miles out of Denver, the 740i cooling system blew up in a cloud of "steam." The car was towed at dealer expense back to Denver where they replaced some parts. I picked up the car several weeks later and within a couple of miles, it was overheating. I took it to another BMW dealer (Co's in Ft. Collins for whom I was a co-driver in the Escort World Challenge series.) They finally determined that the head and block were warped. BMW said that the temperature gage does not indicates temperature if the coolant level is low and gave me a $1000 credit for a new engine. I was not happy. If I would have had the car towed from the top of Loveland Pass, BMW would have paid for the repair under warranty.

I paid $10,000 for a new engine and began the transition to Mercedes after decades as a BMW enthusiast. (I was BMW CCA's first webmaster, my 1st BMW was a 1968 model year 2002 - one of the first in the country, president of the Rocky Mt. Chapter and co-chair of two week-long Oktoberfest celebrations.) So now, because of a poorly designed radiator, I am firmly in the Mercedes camp. But my best friends are still those from my BMW Club and racing days. Be thankful that you only had to replace a hose clamp.

 

Welcome to the club. Standing in parking lot waiting for it to cool down so I can get home with no coolant. there are two connections there. First one failed. Thought no bigger replaced with adjustable clamp. Added coolant. Then few month later second one failed. But this time around took a headlight with it. Check your headlight connections... so topped it up replaced that one with a clamp. Now it failed second time. 😪 so um need to figure out wtf is wrong with it. Temperature gage shows perfect temp always. Only when obviously I drive with no coolant it goes past 90. So it's working. Anyone has any ideas? Time to change thermostat ?

 

Wow! The other one to the right of that one (if you're looking at my picture) failed also, 2x? That's terrible. I will definitely keep my eye on it.

 

Happened on my - now gone - 2015 SL as well. Came out of a meeting and all the coolant was dumped out. That was the only issue I ever had with that car in 5 years. I took it to the dealer and never had the issue again. Don't sweat it, not a big deal.

 

It was a lower rad hose, I was driving, 2014.

 

(March of 2024) Did the exact same clamp fix after 1st failure (identical to your picture) cleaned thouroughly, ran it 3 times, and less than 40 miles later, blew off again. Bought oem new hose and has never happened again. Probably just old and tired.

 

I think @JettaRed had the same issue, or similar not very long ago. Something about him coming out of a store and whoosh, fluid all on the ground. It was also a relatively easy fix..

 

Those can also fail if you put too much side force on them.
If someone has done some work in that area, and pushed it too hard to the side, it can break it's bond/seal.
I've seen this happen on that style of hose. Especially as they get older and more brittle.

(but they do fail too)

 

Yep. Kinda out of nowhere it happened. The hose slipped off the T connector. It had the "permanent" band on it so that Mercedes can sell you a $120 part. I did keep my failed hose and put an upgraded clamp on it (meaning I spend $7 instead of $2.50 on the clamp). Coulda probably just gone with that.


Coolant hose slipped off T

Factory band

New clamp for repair

 

I had that happen while driving in my Saab on an interstate many many years ago, except in that case the hose blew open. I pulled over immediately and had it towed. No long-term effects on the engine. Over time coolant hoses lose flexibility.

The temp fix is to replace the clamp, but the permanent fix is to replace the hose as well.

 

Is there a rule of thumb to replace hoses & clamps after ___ years? Had a similar failure on a 12 year old vehicle a few days ago so I am starting to wonder if I should do some preventative / preemptive replacements

 

Hoses should last a long time. I'm not aware of a change interval for them. I would check them for surface cracks and squeeze to verify they're still flexible. You may also want to push/pull the hose near the clamp to see if there's any movement at the clamp. My guess is the hose wall shrinks in thickness with age and the clamps lose grip.

 

Good point. Coolant is slippery. The parts guy thought that coolant gets between the hose and whatever it is connected to, and then works its way off.

 

I had this happen to my 2014 SL550 a couple of weeks after the dealer serviced my car. They claim it was nothing they did. I believe they overfilled the reservoir during service and the hose was eventually forced off. It happened as I entered my garage after a trip back from the airport. Had I had the "economy" feature engaged, it likely could have happened along the way.

 

Doubt the dealer overfilled the coolant. And if they did, excess coolant will spill out under pressure. I think this is just something that happens randomly, more often then we think. It seems that it happens after driving.

 

It's a completely closed system. Excess coolant will cause this to happen.

 

I will have to check my expansion tank. I know there is a drain on the neck of the tank and the "valve" is the seal on the cap. But, I could be wrong. Seems to me that some kind of pressure release would be designed to prevent blown gaskets and hoses normally.

 

Same thing happened to our 2016 SL400. The "T" blew out and we replaced everything associated; hoses, clamps, etc. About $120 in parts and $650 in labor.

It happened on the highway at night and the entire dash lit up with red lights (low coolant warning). Pulled over and we could see what happened. The dealer said warranty (extended) didn't cover it. I was suspicious, as to what would have blown those pieces out of the blue.

Oh well, working on replacing the 3rd windshield right now, $2,400 a pop.