Coolant leak - fuel filter housing?

[w204benz]

I got a "top up coolant" warning while driving yesterday. Temperatures remained stable so by the time I got home I forgot about it. When I remembered to check a few hours later I found the expansion tank completely empty. It took all the coolant I had and a bit of DI water - about 4L to top up, although I heard a fair bit pouring out as I was doing so (I think the thermostat was still open - it holds on to the coolant while cold).

I found plenty of coolant on the left side of the engine, right up to the fuel filter housing, so I'm suspecting this has failed - I believe it's a common problem on the OM651.

Is there any other reason for the area where the housing connects to the engine to be covered in coolant? There are puddles of coolant in the housing's recesses, but with the engine running I don't know if the movement I'm seeing is the leak or just engine vibrations.

I'm fairly certain the area should be dry, but could the coolant be coming from somewhere else?

If someone can confirm that's most likely the problem, I'll order a new housing. Looks like it might be a possible DIY job. Has anyone done it, and more importantly is it as easy as it looks?

 

[tpn]

There are only two types of original fuel filter housings on that engine; those that are leaking or those that are about to leak. The plastic edge at the bottom of the O ring is very weak and that is where they leak.
There is a modified version available. It is relatively cheap to buy-I changed one last year-, I think somewhere around £30.00.
Blow the water out of there and see where it is reappearing from. There are water hoses onto that housing, as it acts as a diesel heater also. Check all of those.
Open the clips lift the filter out-no need to disconnect the pipes-and have a look into the housing.
I have not seen them to leak but... The housing also usually leaks slowly but...
It is not as easy as it looks to change, the EGR cooler is the main problem. Check the seal in that also and if you are splitting it from the EGR have a new seal available. and if you are looking for the bottom bolt holding the housing it is via a socket extension through the bottom of the housing.

This thread has a video where the inlet manifold is removed but it will give you an idea of the diesel housing. squiggley sockets/extensions are a must to save a lot of swearing.
https://forums.mercedesclub.org.uk/...-efficiency-estate-egr-valve-location.194593/


Safety Warning: don't have headphones on for the first 10 seconds of the video unless you want to blow your eardrums

oh and check everything while you are in there including the oil cooler.

 

[w204benz]

Thanks for the tips. There I was struggling to mop up the coolant - don't know why I didn't think of blowing it out!

A fresh puddle of coolant appeared once the engine got up to temp, so I guess that confirms the source of the leak. It's almost certainly the original housing judging by everything else in the engine bay, so it was only a matter of time.

The dealer has the updated version in stock, not too bad at €50. I'll probably let my mechanic fit it though - I'm not much of a car guy and I'll probably regret starting the job before I'm half way through (especially since I don't have any squiggly sockets).

 

[tpn]

The blast of air is great. It is not a difficult job to change, just fiddly. £50.00 sounds a tad dear but everything has shot up in price recently. I think the dearer priced ones include the EGR seal; If not make sure you get one.

 

[w204benz]

Well, with only one dealer in the country it's to be expected, but I couldn't source one from elsewhere any cheaper and certainly not any faster than popping in to the dealer.

With the new parts on hand I am tempted to have a go at it, but the mechanic has done it before and he can squeeze me in in a couple of days, so probably best to leave it to someone with the proper tools. Besides, considering how often I drop stuff deep in the engine bay when messing around under the bonnet, a fiddly job is probably something I should avoid.

 

[tpn]

Rule number one: Take off the undertray before you start

 

[ajlsl600]

Rule nu 2.. Always have a small magnet on a cord or stick magnet.

 

[w204benz]

Rule nu 2.. Always have a small magnet on a cord or stick magnet.

And a claw tool for the non-magnetic stuff.

Although those rules don't help much with stuff that gets wedged in some dark recess before reaching the undertray!
Maybe I've just got bad luck, but spending ages searching for dropped stuff with a mirror or borescope happens far too often for my liking. Retrieval is usually the easy bit.

 

[ajlsl600]

I get that. Only stress free way is to be in no hurry. But sans workshop I don't often hav that option, snow, sleet, rain no level parking now I appreciate my great French house, workshops.

 

[w204benz]

I, too, lack a workshop. It's a quiet street but I'm still limited in what I can tackle. Then again I don't know much about working on cars, so it's probably a good thing I can't be tempted to have a go at the bigger jobs (I doubt that would end well).

I would have had a go at this one, but I quickly discovered I lacked the right tools to reach most of the bolts.