Warning Light and Temperature Issue

[alistairgd]

2013 W204 C-Class - engine management amber warning light checked out at dealer today - "coolant temperature below spec" error cleared as no fault found, coolant thermostat heating element checked.

So, the problem is, I think there is still a problem.

The car has for 3 years sat at just under 90 degrees regardless of how it is being driven or ambient temperature. Once it is up to operating temperature, it has never fluctuated.

Today I take a closer look during a long drive, and notice that the temperature is fluctuating from high 70 degrees to it's normal of high 80's.

I also notice that I do not seem to be getting "hot" through the heating system like before - I need to set the controls to 25 degrees before anything comes through the vent at what I would describe as hot.

Also noticed that while the heating temp was up high and I had the blower on that the engine temperature dropped to under 80 degrees - never seen it do that before either.

AirCon service done a few weeks ago along with a full 3 year service.

Seems to me there's an temperature management issue - welcome any comments.

 

[Stratman]

Thermostat.

 

[alistairgd]

Ah just found this...

If the thermostat becomes stuck in the open position, there is continuous flow of coolant into the radiator causing the engine to run cold. Overcooled engines run inefficiently, which leads to increased fuel consumption and higher emission levels and engine parts enduring more wear. In addition, the car interior will not heat up properly

Sounds exactly like my issue, the thermostat is perhaps starting to stick, as it is running at normal temps for most of the time... and the engine running cold is what triggered the engine management warning in the first place.

I would have expected a MB thermostats to last longer than 30k though....?

 

[Ted]

So would I, but as Stratman has said, It's the stat.

 

[ernie]

I would have expected a MB thermostats to last longer than 30k though....?

Not true! Mine went in the C 180 204 at 23k miles and triggered the EML. My dealership checked it twice and updated EML software before another fixed it for good.

Seems to be a common problem.

Ernie

 

[alistairgd]

Not true! Mine went in the C 180 204 at 23k miles and triggered the EML. My dealership checked it twice and updated EML software before another fixed it for good.

Seems to be a common problem.

Ernie

Thanks for the info! What was the fix - software?

Also, can you please let me know if your engine temp shows a drop of a few degrees when you put the blower on hot - I can't say I've noticed mine doing this before...

This is how my temp looks once engine is up to temp, it used to stay there all the time, now I see it dipping below 80 degrees if I put the blower on - not sure if this is what triggered the low engine temp warning.

 

[ernie]

alistairgd said 'Thanks for the info! What was the fix - software?

Also, can you please let me know if your engine temp shows a drop of a few degrees when you put the blower on hot - I can't say I've noticed mine doing this before...'


Sorry, I should have made it clear that the fix was a new thermostat. The software updates were red herrings and the car only went for 200miles before the lamp came on again both times. I don't know what Dealership you use, but it was MB Grangemouth that fixed mine.

With my original t'stat there was a noticeable fluctuation of temperature along the lines of what you are saying (actually on 2 C180s, but one was written off before I could get it checked) before it triggered the EML and looking back it was probably due to it sticking.

Neither of our C180s saw a winter in my ownership with a dickie 'stat, so I can't really say if the indication changed when using the fan.

Ernie

 

[ringway]

That temp is bang on. Anywhere between 80-90 is ok, but the nearer to 90 the better.

 

[alistairgd]

Warning light came back on again, now they seem to have confirmed the fault, and it's not a cheap fix.

Stored fault for heating element at coolant thermostat, coolant thermostat would have to be replaced and to access this the intake manifold has to be removed !! £538

 

[Kersidan]

£538 sounds ridiculous. Stats do go 'off' over a period of time, not necessarily sticking but opening too early and not allowing the engine to reach correct operating temperature. Not good for diesel engines and DPF's. I'd get a quote from a recommended Mercedes specialist in your area. Doesn't need to be done by a MB dealership. MB parts must be used though.

Mark

 

[alistairgd]

Thanks. The quote came through the e-mail in a fancy service quote email (total work was £1250 'cause tyres and brakes need routine replacement too).

I gave them a phone and he has suggested keeping the car tonight and testing it from cold in the morning to "double check" it is the heating element at the 'stat.

I actually thought the price sounded about right if a manifold has to come off, that's surely quite a big job.

 

[markjay]

1. Is the car now out of the manufacturer's 3 years warranty?

2. Did it have dealer service so far? If so you should be able to request full or partial contribution based on 4th year Goodwill warranty.

 

[alistairgd]

Hi Good question.

Do when the light came on first time in December it was 6 weeks out of the 3 year warranty! Now it is still within 6 months of the warranty.

And yes all work by them so far.

So yes I will be asking for a hefty contribution.

 

[alistairgd]

Fair play (once again) to MB, the warranty team offered to pay almost 80% of the £528 bill for the thermostat heater - without any back and worth.