SLK32 Coolant loss issues

[Matt32AMG]

Ok guys,
Quick quiz...

I’ve started to notice my 32 is using coolant. I flagged this about 2 months ago with the dealership but they failed to Identify anything untoward, so they topped up the header tank with coolant + antifreeze with a keep an eye on it brief.

Well doing the checks I’ve had to put in another litre since it was last topped up by the dealer. Again there is no obvious signs of a leak.

So my question is without scaring myself is this flagging possible impending intercooler issue?

 

[BlackC55]

Possibly. It needs to be pressure tested and then inspected fully

 

[Matt32AMG]

Possibly. It needs to be pressure tested and then inspected fully

Hmmn I'm guessing thats something you could do (pressure test and replace if required), if it has failed what would I be looking at to replace it do you think? any ideas

Thanks Matt

 

[Matt32AMG]

I completed a cold start test this morning. So with coffee in hand I watched the engine come up to temperature. Fan kicked in at 82/83degrees. No water was dumped on the ground via the overflow pipe. No water vapour present from the exhaust after a couple of minutes after startup. Engine idles smoothly. No emulsification in the oil filler cap now what?

I guess the next step is get it pressure tested.

So I couldn’t sit and twiddle my thumbs having done all the driveway tests I could think of, so I bit the bullet and went down to the dealership against my better judgment, and got my cars coolant system pressure tested…

The Result showed it was fine, no leaks or deficiencies detected, so it was then block tested, the result showed again it was fine, no leaks, which on the face of it is good… except where is over a litre of coolant going in the space of 2 months, and less than 500 miles covered since the cooling system was last topped up? (2 litres were added back then)

This is particularly strange given that until this year, I have never ever had to top up the cooling system between services in the eight years I’ve owned the car. Same can be said about the oil, my car doesn’t use any.

The only explanation that has been offered thus far is that the AMG engines do run hotter (Not sure if that’s right or not), and if it’s a minor leak, it maybe evaporation, however I don’t thrash the car and I don’t drive it any differently really than when I first bought the car, so I’m not sure I buy into this theory.

They have suggested doing an extended pressure test i.e. leave it all day under test to see it there are any leaks. This is scheduled to happen in a week’s time. I'll keep you posted.

Oh and I've been assured it’s not intercooler failure.

 

[Smiley]

well it has got to be going somewhere - the story about AMG engines running hotter is BS - a modern car should not require the coolant to be topped up ever. Maybe you should try somewhere more competent? A litre in 500 miles is quite significant.

 

[BlackC55]

Hmmn I'm guessing thats something you could do (pressure test and replace if required), if it has failed what would I be looking at to replace it do you think? any ideas

Thanks Matt

It all depends where the coolant is going.

You must have a leak. I am sure of that.

 

[Matt32AMG]

well it has got to be going somewhere - the story about AMG engines running hotter is BS - a modern car should not require the coolant to be topped up ever. Maybe you should try somewhere more competent? A litre in 500 miles is quite significant.

Agree on all points. To me the theory about AMG engines running hotter smacks to of clutching at straws

 

[Matt32AMG]

It all depends where the coolant is going.

You must have a leak. I am sure of that.

Agreed, but the bizarre thing is where to?? It beats me and all the pressure tests so far undertaken have resulted in showing up nothing

 

[Swozza]

Had a similar issue. Its was a very slow coolant leak and MB failed to spot it the first time I took the car in. Turned out to be a very small hole in the coolant hose. We have the same engine maybe worth a look at.

 

[gazz]

I had a minor leak from the bottom hose on my C32, which has a very similar engine. Took a while to find it...
I have also had the charge cooler matrix below the supercharger fail. It initially manifested itself as a slow but regular coolant loss, with no obvious leaks. Finally decided to pull off the plenum chambers (the alloy bit with AMG logo raised on the surface, one each side). The leak was then quite obvious, with crusty white traces all over the surface and backs of the inlet valves.

Cooler was expensive is all I'll say!

 

[Matt32AMG]

I had a minor leak from the bottom hose on my C32, which has a very similar engine. Took a while to find it...
I have also had the charge cooler matrix below the supercharger fail. It initially manifested itself as a slow but regular coolant loss, with no obvious leaks. Finally decided to pull off the plenum chambers (the alloy bit with AMG logo raised on the surface, one each side). The leak was then quite obvious, with crusty white traces all over the surface and backs of the inlet valves.

Cooler was expensive is all I'll say!

Hi Gazz,
Thanks for your input and sorry to hear your tales of woe!

A couple of questions for you if I may:
At the point you removed the plenum chambers, was that after you'd been down the same road as I have to date, with all the extensive pressure testing including block testing? The dealership removed the bottom sump guard to gain access to bottom hoses while undertaking the pressure test and after careful inspection derived absolutely nothing, no intercooler problems nothing. Just bizarre.

If it was the charge cooler matrix that failed, what do you call expensive? The bottom line here is whatever the cause, I will clearly have to address the problem.

regards

 

[GordonTarling]

This may or may not help - many years ago, I had a Volvo which was also losing coolant - took me and the dealers around 6 months to discover that it was the water pump shaft seal that was leaking. When the engine was hot and running, the leaking coolant was hitting the pulley and just 'disappearing'. This didn't show up on any pressure test.

 

[Smiley]

Slow loss of coolant can be the start of water pump failure - usually there is a little tell tale dribble of green underneath the pump - of course if the loss is small it all evaporates with the heat of the engine.

 

[Matt32AMG]

Water pump theory could hold water, (excuse the pun), will investigate further, though if it's in the early stages it's going to be hard to spot, for reasons already highlighted. On cold starting tests there is as yet no evidence of a leak in that area.

Anyway thanks I will keep an eye on it.

 

[gazz]

Hi Gazz,
Thanks for your input and sorry to hear your tales of woe!

A couple of questions for you if I may:
At the point you removed the plenum chambers, was that after you'd been down the same road as I have to date, with all the extensive pressure testing including block testing? The dealership removed the bottom sump guard to gain access to bottom hoses while undertaking the pressure test and after careful inspection derived absolutely nothing, no intercooler problems nothing. Just bizarre.

If it was the charge cooler matrix that failed, what do you call expensive? The bottom line here is whatever the cause, I will clearly have to address the problem.

regards

I had spent some time worrying, and had conducted a thorough visual inspection and litmus block test for combustion gasses in the coolant, all of which had proved fruitless. After researching on some American forums I actually found a picture of the inlet tracts of an afflicted vehicle. This prompted me to take the plunge and have a look. Mine was the spitting image of it!!
Luckily I own a small motor repair shop, so labour is all my own, but to replace cooler the supercharger has to come off, complete with inlet manifolding. Quite a bit to it, but no special tools required. Cooler was circa £800+VAT IIRC. A few gaskets required too. Cleanliness vital, as you will have open inlet tracts right down to the valves. No dropping bits down there!!!
Cooler is an interesting piece - carries a Garrett label, handmade too (in mexico)

 

[Matt32AMG]

I had spent some time worrying, and had conducted a thorough visual inspection and litmus block test for combustion gasses in the coolant, all of which had proved fruitless. After researching on some American forums I actually found a picture of the inlet tracts of an afflicted vehicle. This prompted me to take the plunge and have a look. Mine was the spitting image of it!!
Luckily I own a small motor repair shop, so labour is all my own, but to replace cooler the supercharger has to come off, complete with inlet manifolding. Quite a bit to it, but no special tools required. Cooler was circa £800+VAT IIRC. A few gaskets required too. Cleanliness vital, as you will have open inlet tracts right down to the valves. No dropping bits down there!!!
Cooler is an interesting piece - carries a Garrett label, handmade too (in mexico)

Hi Gazz, thanks for your response....
Oh boy, why do I have a feeling deep down this is going to be the expensive solution to this paricular issue.

I totally appreciate cleanliness is vital, what with open inlet tracts right down to the valves, (if this is the route I have to go down).

Thanks again for you input I guess given the lack of any other pointers thus far, like you my options are becoming limited.

BTW Did your car display any initial hesitation on startup? kind of like a quick mild cough that cleared almost immediately?

Regards

 

[Matt32AMG]

Update My car has been on pressure test all night and morning……
The results….no leaks. They even poked about under the SC and in the V….No leaks, no evidence of leaks. Block tested again…No leaks….

Bizarre...

 

[kwakdonut]

Taking things back to basics and, not actually knowing if this would make a difference, but have you changed the cap on the coolant reservoir at all? Back in the good old days of easy-to-work-on cars, a dodgy radiator cap would allow coolant to run out of the overflow pipe, which of course, vented under the car and therefore no evidence!

Am not sure if the caps do such a thing these days, but just a thought.....

 

[Matt32AMG]

Taking things back to basics and, not actually knowing if this would make a difference, but have you changed the cap on the coolant reservoir at all? Back in the good old days of easy-to-work-on cars, a dodgy radiator cap would allow coolant to run out of the overflow pipe, which of course, vented under the car and therefore no evidence!

Am not sure if the caps do such a thing these days, but just a thought.....

Hi, it's a good thought , except that on the 32, the header tank cap is different from say that of the SLK200 or 230, in that it has what can best be described as a bottle top screw on type of cap, which takes maybe four or five full turns to seat properly as opposed to the conventional push down, (Knock on hub style of Cap that has two ear’s to aid location and tightening) I.E. push down and turn once to locate type. (Hope that makes sense).

That aside, I can’t help thinking if it was leaking from there I feel pretty confident I’d spot it. Thanks for the thought all the same, appreciated.

 

[gazz]

Update My car has been on pressure test all night and morning……
The results….no leaks. They even poked about under the SC and in the V….No leaks, no evidence of leaks. Block tested again…No leaks….

Bizarre...

If the cooler matrix is leaking there will be no external signs of coolant. It will all be going out through the engine. Get them to pull one of the plenums off if it continues to worry you. Just one simple gasket will be required to do this, at about £8 IIRC. Would take fifteen mins, and you would know for sure then.