W212 E350 cdi coolant leak

[b21playa]

Hi all

Wondering if someone can help me with this leak I have. I initially thought it was the outlet elbow from the block but having changed this the issue is still there.

I can top-up and get the light on within 8miles, used to be every week I topped-up but getting worse. I can see water on the front undertray but as everything is so crammed I have no idea where it is coming from, although I'm 99% sure it's from the front. I have pressure tested the system and it does loose pressure. Doesn't seem to be any water in oil or vice versa and no loss of oil luckily. I have changed the coolant tank cap as I have read these can go.

I have purchased a water pump kit thinking it could be leaking from the pulley or gasket as the car has 158k on it now. Issue is how can I be sure it is that, and also how do I go about stripping down the front to get to the water pump?

This is my only car at the moment so a bit stuck, have to keep topping up and watching temp gage, it never over heats.

Many thanks in advance, any help is much appreciated.

 

[Droverunner]

How are you looking for the leak... opening the bonnet and peering in... on home ramps or a jack and axle stands??

Often something like this is so much more easily located with engine covers off top and bottom plus being on a proper lift. Another way is with the under tray/s off run it over a clean dry floor (or opened out cardboard box maybe) and get a better idea of where the drips are coming from.

In a way good you can see coolant leaked into the under tray as it shows it's an external leak and is a start towards locking the source.

 

[Mr Greedy]

Possibly the seals on the radiator top hoses. If you buy new hoses you get new seals, but I believe you can get the seals direct from Merc for not much.

 

[Jim2]

Does this engine have the heated fuel filter, where the hot water from the engine block is circulated through the fuel filter too? In the OM651 engine, its a very common Leak issue.

 

[b21playa]

How are you looking for the leak... opening the bonnet and peering in... on home ramps or a jack and axle stands??

Often something like this is so much more easily located with engine covers off top and bottom plus being on a proper lift. Another way is with the under tray/s off run it over a clean dry floor (or opened out cardboard box maybe) and get a better idea of where the drips are coming from.

In a way good you can see coolant leaked into the under tray as it shows it's an external leak and is a start towards locking the source.

Hi

I have looked from both the top and also removed the undertray to look from beneath. Not much space to actually pinpoint leak, at first I thought it was the outlet elbow hence why this was changed.

Yes I'm glad its external rather than internal

 

[b21playa]

Possibly the seals on the radiator top hoses. If you buy new hoses you get new seals, but I believe you can get the seals direct from Merc for not much.

I have changed the seal on the left hand hose and fully replaced the right hand hose already - both genuine Mercedes parts

 

[b21playa]

Does this engine have the heated fuel filter, where the hot water from the engine block is circulated through the fuel filter too? In the OM651 engine, its a very common Leak issue.

I'm not sure if the OM642 has this

 

[b21playa]

Just an update for anyone who may come across this....turned out to be the water pump. It was the original from 2010 and managed 158k (not bad)

The bearing was shot and it was leaking past this. New one installed along with new idlers, tensioner and belt and running great again. Just been through MOT the other day and all is well apart from rear lower thrust arms, so that's the next job along with alignment and 2 rear tyres.

 

[Droverunner]

That's a good result. It was a chirrup on the aux belt that started us on this trail a few years ago on Mrs D's CLK. Ended up seeing the earliest sign of a leak from the pump so did belt, pump, tensioner, aux pulley and alternator pulley.