E Class E220 Estate S212 OM651 Coolant Leak -- Solved?

[steveq]

I want to share a reasonably easy solution to a coolant leak that I had.

My E Class Estate started losing coolant a few weeks ago.
It first gave me the warning on the dash saying that the coolant was low. When I checked the expansion tank it was about half full. I added coolant and the message went away but in a day or two the message was back.

I had replaced the coolant pump a few years ago as it was leaking but have covered less than 20,000 miles since.
I checked it and couldn't see any leaks there.
I also checked the fuel filter housing for leaks both with my naked eye using a torch and poking about the area with my endoscope camera. There were no leaks visible there either.

The coolant only seemed to leak when the engine was up to normal working temperature.

Looking here and elsewhere on the net, I could see that there are many other potential leak areas -- EGR, heater hoses, engine core plugs, etc.
No obvious leaks anywhere.
I was going to get some UV or fluorescent dye to put in the coolant to try to find the leak.
Before I did that I got some food colouring in the kitchen that was used for baking (not by me) and picked the brightest colour (light green). I diluted a few drops into some water and put that into the expansion tank.

With the engine running and a powerful torch (and keeping the fingers clear of the serpentine belts) I methodically went around all sides of the engine.

I eventually found a steady drip from the coolant hose going from the thermostat to the radiator at the top RHS of the engine.
You might wonder why I didn't spot it instantly. To my defence it wasn't that easy to see -- it drips down to an area where the coolant goes straight down to the undertray and out. Also it only leaked when the thermostat was open. Neither are great excuses and I was probably more focussed on looking at the trickier to get at areas.

I initially thought that I would need to replace the hose but then found a YouTube video where someone just replaced the little rubber sealant ring at the end. They replaced the ring at the thermostat end of the pipe but the idea is the same.

Here is a link to the video I found:-

He had a lot of sealant all over the hose and connector. I didn't have or need any of that stuff.

I got the replacement rubber ring from a local MB main dealer for just less than €10. I ordered it in and they had it next day. The part number was A00269976745.

I syphoned the coolant out of the expansion tank into a bottle.
I then removed the spring clip from the radiator end of the hose pipe. I put a funnel right under the join from the hosepipe to the radiator with a small soft plastic bottle underneath it to collect any coolant that leaked.
I removed the hose pipe -- less than a quarter of a pint of coolant came out and went into the funnel and bottle.

I took the old rubber ring off and put the new one on.
I pushed the hose back and then the spring clip.
I put the coolant from the bottles back into the expansion tank plus some water to bring it up to the correct level.

Brought the car for a run to get it fully up to temp and then checked the hose for leaks while it was running. Good news -- No leaks visible.
I'll keep an eye on it for the next while but I think I got away with a very easy & cheap solution to a problem that could have been much trickier, more time consuming and expensive to fix.

 

[mioba]

Good work.

I find sometimes when searching for leaks in hard to see places is to simply run your hands and fingers along the area and check for wetness on the hands and fingers.

Well done on your fix!