Help please! Coolant leak

[fakyata]

Hi folks!

I've had a coolant message coming up in my 06 W221 320cdi. I have topped it up hoping it just needed a top-up, after 10 miles message was back again, took the car for a quick inspection and was told "oh man if it's taking coolant you need a new engine" type thing... took it to another engine specialist who did a pressure test on the system - that came back normal, then did the second test for pressure build-up in the system during high revs ( apparently should the pressure build up in the system when the engine is running, that would indicate HG issues or a crack in the engine somewhere ) that was ok as well no extra pressure added to the system. As a precaution, he advised to change the expansion cap to new, do a full cooling system flush with new fill and addition of 2 bottles of the Steal Seal gasket sealant. This was done the next day at my local garage. I went shopping this morning and after 10 miles again the dreaded "top-up coolant" message popped up. I filled it with water so I could get back home. After an hour of the car being left to cool down on the car park, I went to check the levels again, I've noticed a lot of sprayed white residue from the coolant on the metal casing around the engine and around the expansion tank so I thought I will turn the engine on and to my surprise an instant leak from underneath. this wasn't just a small patch it was a proper dribbly leak! I had my phone on me so did a quick video.

Any idea? I'm dreading the repair could end up being in thousands which would be not very economical considering the age of the car.

 

[Jim2]

Well, a leak like that,should be very easy to locate, up on a lift, remove the under shields, and from what your video shows, you will need an umbrella..but I'd keep far away from any mechanic who recommends putting anything other than the approved antifreeze in the cooling system .Identify the cause, and fix it.

 

[AMGeed]

Check the water pump for leaks. With the engine off and cooled down put your hand underneath and see if its weeping from there.

 

[fakyata]

Well, a leak like that,should be very easy to locate, up on a lift, remove the under shields, and from what your video shows, you will need an umbrella..but I'd keep far away from any mechanic who recommends putting anything other than the approved antifreeze in the cooling system .Identify the cause, and fix it.

Thanks! Yes fortunately the S class came with brolly so now I will have a chance to use it hah. This is sadly a reality of living in the Bradford area... 95% cowboys, 4 % robbers and 1% hiding away. After recent wheel alignment, I have almost ended up 6 Ft under when the garage has forgotten to screw in all 5 nuts in the back passenger alloy... I genuinely thought the air suspension went but the fact was that the wheel started to come off the shaft just after I've lost all 5 nuts on the way back home!

 

[mioba]

Jeepers thats a lot of water.
Beyond the posts above which are spot on, dont use those garages again where you was before. Absolute rogues.

 

[fakyata]

Thanks folks ! I've booked the car tomorrow with another local garage ( not convinced) I've also looked around and it seems there is some loose plug hanging around on the top of passenger manifold... ( I guess forgotten by the service man last December ) I've also noticed that when the key is turned into 2nd position before cranking There is a fairly loud rattle coming out of the small black box that sits on top of the water pump ( sort of triangle shape black box )

I'm actually looking forward to tomorrow morning and finding our all the bad wonders with my car

 

[DSK]

The only thing I will add is, something like that should be easily traced by a decent mechanic, be it a great chap working from home to a seriously great tech in a dealer garage.

Radiator caps can go but, they cause a slow loss of coolant

On other cars where a leak has been significant, I have found the following;

- split in the expansion tank (gets ****ed out under pressure but looks fine when cool and standing)
- split in the expansion tank coolant hose (hose clips hiding split in the coolant hoses)

 

[Jim2]

Or the "invisible "leaking from the fuel filter housing..I had that experience myself, but its so common, the garage had a stock of them...

 

[fakyata]

Quic update, the leaking coolant has been identified as a faulty water pump so that's being replaced tomorrow in the garage ( pending part delivery) .On the other had, this is a new noise that has appeared few days ago along with the leaking coolant. It starts with the key being in ignition mode but also carries along when the engine is on. It seems to be coming from the small black box which also vibrates beside the noise. Any thoughts?

Ps. I'm so thankful for all the help so far! This forum is amazing and if I keep reading more and watching more YT I will end up rebuilding this engine myyself lol

 

[star]

The noise your hearing is from the throttle body.
I think the plug you refer to as to being left off in your first post might be a spare that isn’t used on some 642 chi engines.