Engine management light

[Suzukimac]

Just wondering if anyone could give me a guide line price for changing coolant temperature sensor on my C350e .
P0128 coming up has a problem
Thanks in advance

 

[OneForTheRoad]

Stuck open thermostat likely.

 

[Suzukimac]

Stuck open thermostat likely.

Many thanks for your reply .
I think you might be right , has the light has now turned off . So maybe has freed itself . Regards

 

[markjay]

If I am not mistaken then your C350e will have the M274 2.0L petrol engine.

If so, then the cost of replacing the thermostat is £700-£800 at the dealer, or half that at a good independent specialist.

 

[markjay]

Many thanks for your reply .
I think you might be right , has the light has now turned off . So maybe has freed itself . Regards

Just check that the temperature gauge gets quickly to 80 degrees, and then remains well above 80 at all times. If it dips occasionally below 80, the thermostat is faulty.

 

[Suzukimac]

If I am not mistaken then your C350e will have the M274 2.0L petrol engine.

If so, then the cost of replacing the thermostat is £700-£800 at the dealer, or half that at a good independent specialist.

Many thanks for your reply.
It's good to have a idea of the cost .
But luckily for me now the light has turned of . But still may return.
Regards

 

[markjay]

Many thanks for your reply.
It's good to have a idea of the cost .
But luckily for me now the light has turned of . But still may return.
Regards

Also, you need to read the codes with STAR (or iCarsoft or Carly).

There's a Mercedes-specific fault code for failing thermostat, it says that the coolant temperature is below the expected values.

 

[Surgi]

Stuck open thermostat likely.

Mine thermostat stuck opened looks like it, coz just after engine starts, in 5 min there are pipes already warm near the radiator. So possibly ned to change a sensor only, you recon? W204 651.911 restyle...

 

[Surgi]

If I am not mistaken then your C350e will have the M274 2.0L petrol engine.

If so, then the cost of replacing the thermostat is £700-£800 at the dealer, or half that at a good independent specialist.

Hi.
Can be that engine management light won't turn on if thermostat is stuck opened?
Thanks.
Om651 911 W204

 

[markjay]

Hi.
Can be that engine management light won't turn on if thermostat is stuck opened?
Thanks.
Om651 911 W204

The M274 has an electronically-controlled thermostat, so the ECU knows if there's a problem with it and will flag up an EML.

The older M271 has a simple thermostat, so the ECU doesn't know if it failed, hence no EML.

I don't know what type of thermostat the OM651 has. An open thermostat will result in an engine running cold at all times. An EML should be checked with a scanner (STAR / iCarsoft / Carly).

Hope this helps.

 

[Surgi]

The M274 has an electronically-controlled thermostat, so the ECU knows if there's a problem with it and will flag up an EML.

The older M271 has a simple thermostat, so the ECU doesn't know if it failed, hence no EML.

I don't know what type of thermostat the OM651 has. An open thermostat will result in an engine running cold at all times. An EML should be checked with a scanner (STAR / iCarsoft / Carly).

Hope this helps.

Hi.

On 651 thermostat have two connectors, one is for coolant temperature but another to activate it as soon as I understand.

What a bit weird thing is, that temperature on a dash, usually OK, around 85-90 on a motorway, but sometimes it drop for 10-15 degrees down, takes long time to warm engine up till work temperature if on idle. If driving on dual carriage way, can drop to 70.

So I presume its stuck on big loop, or not working properly, but still supply with required temperature, because a sensor not give any fault codes.

I have scanned vehicle with xentry passthru, no faults related temperature where discovered.

 

[markjay]

Hi.

On 651 thermostat have two connectors, one is for coolant temperature but another to activate it as soon as I understand.

What a bit weird thing is, that temperature on a dash, usually OK, around 85-90 on a motorway, but sometimes it drop for 10-15 degrees down, takes long time to warm engine up till work temperature if on idle. If driving on dual carriage way, can drop to 70.

So I presume its stuck on big loop, or not working properly, but still supply with required temperature, because a sensor not give any fault codes.

I have scanned vehicle with xentry passthru, no faults related temperature where discovered.

Yes, this definitely looks like a faulty thermostat.

 

[Surgi]

Yes, this definitely looks like a faulty thermostat.

Left to chose where to buy from)

 

[OneForTheRoad]

Mine thermostat stuck opened looks like it, coz just after engine starts, in 5 min there are pipes already warm near the radiator. So possibly ned to change a sensor only, you recon? W204 651.911 restyle...

They fail internally ,leaving a gap like 3mm . Enough to let water through but also restrict flow , hence you still get heat and a reading. When working properly they stay closed till engine is hot 90 degrees , then open fully.

 

[Surgi]

They fail internally ,leaving a gap like 3mm . Enough to let water through but also restrict flow , hence you still get heat and a reading. When working properly they stay closed till engine is hot 90 degrees , then open fully.

So it isn't bad thing than) been changing coolant, didn't find a drain plug in a head block... (( om651 911

 

[rayasun]

I too have P0128 EML warning light. I've not checked the coolant temperature though.