Theocles

Hi,

I bought a used 2006 E350 last year and been driving it since. Yesterday, the CEL came on while driving home in 40F weather. This morning I checked it with a scanner an it had a P0128 error code, specifying a temperature sensor or thermostat fault. I started the engine this morning to watch the temp gauge on the dash panel, but after several minutes of operation, it showed no rise of temperature and the bar completely empty. I have to believe the coolant sensor must be bad.

Though I'm a decent mechanic, for the life of me, I can't locate the coolant sensor! Researching online, I see other W211's have the sensor just in front-center of the engine, just below the "second blower". My blower appears different and there's no sensor I can see below it.

I've attached some pics of my car.

Can anyone please help me find the coolant sensor on this engine?

thanks!
Paul

temp gauge not showing any temp after running car several minutes

the blower left of center appears different on my 06 E350

body

removed the front engine cover already

kjb55

I would suspect that your error is the Thermostat and the integrated sensor. See picture. Given that the car isn't readily warming up - especially if driving relatively soon after cold start. FCPEuro is a great place for parts.

Theocles

thank you very much kjb55.. that would explain a lot! I'll replace it then.

konigstiger

Theocles

thanks Konistiger! Glad you caught me before i ordered the thermostat, it should be cheaper and easier to start with. I'll check it today and get back with you.

Theocles

i dunno what genius decided to put that coolant sensor on the back of the motor next to the firewall, but it was a b*tch to change, esp for someone with big hands! Tried to use a mirror but finally had to do it by feel!

I swapped out the coolant sensor and no change on the dash temp meter, it's still solid white, even though car reads ambient at 65F. I ran it for about 2 mins and no rise in temperature, so shut it down.

I guess I'l now change out the thermostat.

thanks again!
Paul

05w211wagon

Theocles, if you have a infrared thermometer i would take a few temp readings on some of the hoses and block.

Thanks

Theocles

yeah, good idea, i have one and will check it. thanks!

jim viet

Theocles

I never posted the fix for my original post, but it was indeed the thermostat inside the housing below the radiator hose (what you have pictured above). The rubber gasket on outside of thermostat deteriorated and was wedged between the thermostat. After replacing the thermostat the engine temperature and gauge operated properly.

NewShockerGuy

I just replacement my thermostat and for good measure wanted to do the temp sensor in the rear. I can't even get to it. I used a mirror but I can't for the life of me, get my hands or tool along with a mirror to undo both bolts. What a stupid stupid design from MB... it's sort of absurd.
I guess I won't be changing it.

-Nigel

robbieas

The part is like $10 so it seems like a decent thing to try, but it's an incredible pain in the ***. Avoid it unless you are positive it is defective.

NewShockerGuy

I finally got it. I couldn't let it defeat me..lol.. What a total PITA. Just enough room to get your hand in there and all cut up but not enough to see without a mirror. I was changing the thermostat and for good measure wanted to replace the temp sensor since I bought it. I was able to change out both. Everything seems to be working now, and gets up to temp as expected.

I'm pretty sure mine was fine as it was still showing on the gauge cluster, and the main culprit was the thermostat that was making it take too long to get up to temp. And or it would be a bar or two below the 80c. I just wanted to change it for good measure..lol

-Nigel

calvino

how did you finally get the screw out for the temp sensor?

NewShockerGuy

Determination and persistence...lol

Just keep going till the bolt comes out. But you really are doing it blindly. If there was just a couple more inches it wouldn't be bad, but it is what it is.

-Nigel