Ml420cdi coolant leak

[Ryegault]

Hi folks. Just bought my first "modern" mercedes.

Its a 2008 ml420. Shes a bit up the miles at 170k but this should be no problem for a quality german motor.
Now heres my issue.

Its loosing coolant at a alarming rate, i fill it up with coolant, i can leave it idling for an hour and it doesn't seem to use any. Then I give it some welly for a mile and i can pour about 4 litres in. The system has plenty pressure in it. When i undo the cap, bubbles come rushing into the expansion bottle. There are no visible leaks.


Help please.

 

[texterted]

You'll have to get your coolant system pressure tested.

Fingers crossed it's not a head gasket gone.

 

[wwhatton]

Hi folks. Just bought my first "modern" mercedes.

Its a 2008 ml420. Shes a bit up the miles at 170k but this should be no problem for a quality german motor.
Now heres my issue.

Its loosing coolant at a alarming rate, i fill it up with coolant, i can leave it idling for an hour and it doesn't seem to use any. Then I give it some welly for a mile and i can pour about 4 litres in. The system has plenty pressure in it. When i undo the cap, bubbles come rushing into the expansion bottle. There are no visible leaks.


Help please.

Hi mate

Did you solve this problem? I have exactly the same car but only with 110,000 miles on. The garage is really struggling to diagnose the fault. It's been with them months. Any help would really be appreciated.

 

[Roheetm]

Hi Gents,

Had the same issue on my ML420, turned out to be leaking via the water pump for a while before the pump gave way. One pump replaced and it was perfectly fine again! But to add, my pump failed completely but its worth a check, the pump gets a bit noisy which is a good sign! Good luck!

**Edit just realised we aren't in 2021 any more!**

 

[Jimblob]

Got a ml420cdi 2008, I lose Coolant but car does not overheat, towed a 1500kg caravan 130 miles and temp gauge never went above 90 degrees c, but filled up expansion tank 3 times on journey.
Also tailgate close sometimes off buttons and not others, narrowed it done to fuse box in rear but still doesn't work every time. Any ideas?