2007 w211 om642 Coolant leak from back of engine but can’t find source

[Abluw211]

hey everyone I recently noticed a puddle of coolant under the car. I lifted the car up to see where the leak was coming from but I am having trouble finding it.
The only sign I can see is that it’s dripping down from the back of the engine from the firewall above the oil pan.
Car doesn’t overheat when I’m driving but I have had top it up twice. I’ve left the car on to see if it’ll leak but no luck. I did a pressurized test and I can see it drip down the firewall but can’t find the source. The front of the engine and top of the engine is dry, there’s no mix of oil with coolant and the heater control valve looks good.
Would love to hear any suggestions and any help

Cheers

 

[Mark A]

Sounds like oil cooler seals. Have a search on the forum, it is a well documented problem on the OM642 unfortunately.

if you add your location to your details perhaps someone can point you in the direction of a good indie to confirm and fix.

welcome to the forum.

 

[onefortheroad]

I thought you leak oil when the oil cooler seals go , not water ??

 

[Steve@Avantgarde]

Its more likely to be the actual heat exchanger cooler thats fractured if its coolant. If its the seals then its just oil that leaks. The other common favourite is the bridge between the inlet manifolds.

It's why I always replace the cooler rather than just the seals as the level of work for an additional £120 or so makes it negligable in the long run.

 

[Doug1234]

Another possible could be the engine temp sensor located on the top of the inlet manifold on the right when looking at front of vehicle between glow plugs ,its held in by a push clip and it’s also I think highest point in cooling system. It just has an o ring to seal it. Long shot but possible it could leak and coolant run down top of manifold to rear.
What setup does the egr have coolant wise ?. My 642 Jeep has two coolant pipes but these come off two steel pipes that run around side of engine and I think the Mercedes are a different setup.

 

[Abluw211]

Thank you everyone for your suggestions! I think I found the culprit. The hvac heater hose (part A211 830 3496) had a little hole that fitted under the EGR. I don’t know how I missed it before but after taking out the egr and putting it back on. I did a pressurized test this time with a coolant uv dye and saw it shoot down the back of the engine.
I’m hoping this is the issue. Will confirm once I get the new hose

 

[DREAMER NO2]

Or from valley seals -inlet manifold but i hope its an easy fix for you.

 

[Abluw211]

No more leaks! I put on the new hose and some new clamps and so far so good

Thank you everyone!

 

[mioba]

Good stuff and thanks for the follow up posts. nothing worse than cold threads.

 

[DREAMER NO2]