Mysterious Loss Of Coolant

[rosscls55]

Im stuck folks. My CLS55 (M113K engine) is losing coolant but absolutely no idea where from. Its been to MSL for a pressure test. This confirmed a leak - they went all over it and they could not find the source of the leak. Coolant was drained and oil drained and both checked to see if there was any signs of oil/coolant mixing. No evidence of this, both oil and coolant were clean so head gasket was ruled out.

Ran it on MSL's dyno - pulled 545bhp/647lb/tq. Acid says engine is strong and healthy. Again, head gasket ruled out.

Its also been to my Mercedes indie specialist, they also could not find the leak.

Its now reached the point where im having to top up around a coke can full every 100 miles.

It has had a new ic pump, so it should not be that.

Engine is not overheating, temp always at 80c

This is really pissing me off!!

What shall I do?? Take the whole cooling system apart and micro inspect every hose, component, radiator, etc? Thats gonna cost a bit.

Shall I just live with it?

Or shall I just bung some rad weld in it?

Someone pls help!!!

 

[Numair Aidroos]

@E55BOF care to put 9 years and 8K+ keyboard experience to use here for a fellow in need of help?

 

[Numair Aidroos]

Im stuck folks. My CLS55 (M113K engine) is losing coolant but absolutely no idea where from. Its been to MSL for a pressure test. This confirmed a leak - they went all over it and they could not find the source of the leak. Coolant was drained and oil drained and both checked to see if there was any signs of oil/coolant mixing. No evidence of this, both oil and coolant were clean so head gasket was ruled out.

Ran it on MSL's dyno - pulled 545bhp/647lb/tq. Acid says engine is strong and healthy. Again, head gasket ruled out.

Its also been to my Mercedes indie specialist, they also could not find the leak.

Its now reached the point where im having to top up around a coke can full every 100 miles.

It has had a new ic pump, so it should not be that.

Engine is not overheating, temp always at 80c

This is really pissing me off!!

What shall I do?? Take the whole cooling system apart and micro inspect every hose, component, radiator, etc? Thats gonna cost a bit.

Shall I just live with it?

Or shall I just bung some rad weld in it?

Someone pls help!!!

Better to inspect thoroughly than to carry a Coke Can full of premixed coolant solution per 100 mile distance.

Pay attention to the new pump, it's surrounding area and the thermostat and its lower radiator hose until the radiator.

 

[E55BOF]

@E55BOF care to put 9 years and 8K+ keyboard experience to use here for a fellow in need of help?

Of course, if I can; what help do you need...?

 

[Jobsworth]

Have you checked for chargecooler leak below supercharger? If you remove one of the intake plenums (aluminium bit with ///AMG cast into it) you can see the intake ports and valves. If you have coolant leaking from the chargecooler you’ll see white/green crust in the ports and on the backs of the valves where there should be none.

 

[Jobsworth]

I don’t know if it’s linked, but the only ones I have ever changed have been after intercooler pump failure. It’s only a theory, but I think if the coolant stops circulating what’s left inside the cooler core gets brutally overheated and the cooler maybe cracks internally. Just a theory

 

[rosscls55]

Thank you so much everyone. Well, would you Adam and Eve it. Today, I filled the coolant reservoir to precisely the required level and decided to go for a drive, the aim being to see how many miles it would be before I get a message on the cluster asking for more coolant.

ie To try and get a better understanding of the rate of loss.

I did 240 miles round North Wales and back, during which, no message. Checked the coolant level when I got home. Hasn't moved at all.

This is nuts. For the last month its been losing coolant. I post on here about the problem. The next day it stops losing coolant???

Im starting to think this car is haunted.

 

[rosscls55]

I don’t know if it’s linked, but the only ones I have ever changed have been after intercooler pump failure. It’s only a theory, but I think if the coolant stops circulating what’s left inside the cooler core gets brutally overheated and the cooler maybe cracks internally. Just a theory

Thanks mate. It has a new IC pump, only 3 months ago and MSL couldnt see any leak there

 

[rosscls55]

Have you checked for chargecooler leak below supercharger? If you remove one of the intake plenums (aluminium bit with ///AMG cast into it) you can see the intake ports and valves. If you have coolant leaking from the chargecooler you’ll see white/green crust in the ports and on the backs of the valves where there should be none.

This is def something I will look at. I have heard about this from others. I'll keep you posted. However today, its not losing any coolant after a 240 mile drive. Weird.

 

[pillow]

Bear in mind that the ambient temperature can impact your reading (as well as orientation you park at) so if you are comparing coolant level you need to park at the same angle and measure with the coolant at the same temperature (or as close to) ideally.

I fill my coolant tank to bang on the right level but if it's particularly cold out I know it will read a smidge below the mark. I expect when the summer rolls around it will read a bit higher than the mark (although it's harder to tell how much above the mark it is)

 

[Numair Aidroos]

This is def something I will look at. I have heard about this from others. I'll keep you posted. However today, its not losing any coolant after a 240 mile drive. Weird.

Any update? Did you ever locate the leak site?

 

[Numair Aidroos]

@AMGeed, Angel biscuit, do you have any clue here? Can you help out another member with his tuned amg?

 

[AMGeed]

@AMGeed, Angel biscuit, do you have any clue here? Can you help out another member with his tuned amg?

As the OP hasn't returned for a few weeks maybe we can assume the leak has stopped?
I'll always assist when I can. If I don't reply, someone has the same idea or better than me.

This is def something I will look at. I have heard about this from others. I'll keep you posted. However today, its not losing any coolant after a 240 mile drive. Weird.

 

[Numair Aidroos]

As the OP hasn't returned for a few weeks maybe we can assume the leak has stopped?
I'll always assist when I can. If I don't reply, someone has the same idea or better than me.

Thank you.

 

[rosscls55]

It still exists, and I still have no idea where its leaking from. Otherwise, car is running absolutely perfectly

 

[SL03WLY]

I had similar last year, where it kept losing coolant randomly and couldn't find where. Eventually found it, and it was the vent tube from the coolant expansion tank to the top radiator hose. Didn't look damaged and the hose itself is quite solid, but one end would just slip out without any force so under load it would lose coolant. Also the expansion tank itself, no word of a lie, the other end of the vent tube, I touched it and that hole on the tank crumbled. In my case, some D***head from one of the previous owners thought sealant and glue would do the job. It was I believe a £50 part from dealers.

Part No. 110.

Worth taking a look.