New member

[Delinquentrich]

Hi guys,

New member and a massive issue has caused me to come on here. Bought a lovely ml250 bluetec sport early in 2020 and it’s been as good as gold apart from every 3/4 months it’s been looking for more coolant. Being new to having a big diesel I assumed this was fairly regular. Today I went to add some as I was greeted with a warning to top up and the well is full of black sludge. Local mechanic said it’s goosed (not in those words) and it’s going back to the dealership I bought it from next week as it’s still under a 2 year parts and breakdown warranty.

I guess I’m here looking for someone to try to give me a potentially positive outcome? Do we think they’ll refuse to fix?

Cheers for any advice in advance!

 

[Blobcat]

Hello and welcome,

No engine should be using coolant...

 

[Delinquentrich]

I guess I had a hunch that it’s was pretty abnormal but just wasn’t sure if as it had been a really warm summer it’s had been working overtime with the ac.

It’s at this point that I’ll admit that I don’t know as much about cars as I’d like to but that’s probably fairly obvious by now!

 

[SmartAmg]

Welcome.

 

[sausage]

Welcome. The only thing I can think of is that there are different types of coolant, and mixing them can create sludge in the cooling system. I was always worried about adding coolant to my cars, fearful of creating a sludge/foam. I would probably start with talking to a professional about whether flushing the system out can clean out the crud. Flushing a coolant system is generally a common practice and shouldn't cost much. Halfords will do a coolant change for about £40 but this would likely leave some residue of the old coolant in place, and your sludge puppy making machine would start up again soon after the change. Better to chat to someone who knows and have the system flushed enough to clear it all out - if that is possible. If not, you might need a new radiator, pipes as well as a flush.

Do a bit of searching on Google about it, and do update the post with the outcome It might be fine.

 

[SL63 Mark]

I am a bit confused when you say "the well is full of black sludge". What is the "well" of which you speak ?? Where are you topping up the coolant ? You are not putting it in the top of the engine are you ? You should add coolant in the expansion tank. As above, no modern engine should use coolant, even in the hottest weather.

Knowing little about modern Mercs, but quite a lot about older engines, there are several possibilities from the quite inexpensive to the very expensive.

1. Coolant leak. (best case scenario, hose or pipe, fairly easy fix). As you have kept it topped up, hopefully there is no engine damage from overheating.
2. Head gasket leak, coolant in oil etc. Starts to get very expensive, possible new engine time.
3. Other weird leak from coolant into oil somewhere, e.g. oil cooler. Also not good, if coolant has got into oil.

 

[00slk]

Hello and welcome

 

[sausage]

I am a bit confused when you say "the well is full of black sludge". What is the "well" of which you speak ?? Where are you topping up the coolant ? You are not putting it in the top of the engine are you ? You should add coolant in the expansion tank. As above, no modern engine should use coolant, even in the hottest weather.

Knowing little about modern Mercs, but quite a lot about older engines, there are several possibilities from the quite inexpensive to the very expensive.

1. Coolant leak. (best case scenario, hose or pipe, fairly easy fix). As you have kept it topped up, hopefully there is no engine damage from overheating.
2. Head gasket leak, coolant in oil etc. Starts to get very expensive, possible new engine time.
3. Other weird leak from coolant into oil somewhere, e.g. oil cooler. Also not good, if coolant has got into oil.

Best case scenario (1) above could be as simple as a new clamp/jubilee clip which would be even cheaper than a hose

Whatever you do, do not open the coolant system, bottle/well, remove hoses when the engine has been running, else none of us will find out what the cause of your problem was, well not at least until you are released from the hospital's burns unit.

 

[sausage]

I am not vouching for this, but DAP suggests a flush should sort it out:

The sludge: