MTeezee

Couple weeks ago, my Check Engine light was on for a few days. I went and got it checked and the code was P0128. Read some other posts and it seemed like a Thermostat issue. After a couple days, the light went off and hasnt come back on since. Do I still need to take it to get checked or could the issue be gone? Thanks in advance

jimbo1763

Just got done with that one on my 2007 E350. Needed a new thermostat. Car was taking too long to warm up to operating temp.

It could also be a sensor, but take a look at your temperature gauge when you start from cold and see how it warms.

ozusa

The code means that the engine coolant was taking too long to reach proper temperature. (at least, the water that is where the temperature sensor is, was cold too long.)

I suggest
a) check the coolant level is appropriate
b) start the car cold. If the radiator fan comes on "too soon" then that may be a problem and it's keeping the engine cooler than it should. There is a thread about that somewhere. The controller for the fan is not a separate part on some (most?) W211's, so you have to buy the whole darn fan at great expense if the controller has gone crazy
c) you had a sticky thermostat that freed itself but will stick again some day

In the absence of other information, my bet is on (c). I'd get a new thermostat as soon as convenient. I can't tell you that one day you'll cook the engine if you don't, but you might.

MTeezee

Thanks Jimbo and ozusa. I checked the temp gauge from starting cold yesterday and today. Looks like it takes 8-9 minutes to reach optimal temperature (looks to be around 86 degrees). Since I'm a newbie, let me know if you think that is about right.

Ozusa I will also check for #1 and #2.

jimbo1763

It's not far off from mine with the new thermostat.

My symptoms included a CEL that came and went and finally stayed, as well as a fluctuating temperature gauge once the light stayed on.

foldhero

I have a 2008 e300, it has intermittent problem, sometimes the engine coolant take too long to reach proper temperature, sometimes it was fine. I noticed one interesting fact, when the problem happens, the temperature stuck at about 60°C, while the normal temperature should be 90°C. At this point, if I restart the car, the temperature will go up much quicker and reach 90°C in a few minutes.

Can any one help me to determine what could be the problem? Thanks!

eddieo45

anyone know for sure which thermostat part # is right for W211 E350? After seeing in a W208 forum from 2012 that the part "is $27 at AutoHausAZ", I found 2722000415 for $98.86 and 6462000015 for $57.24

Both seem a big difference from one model to the next.....

konigstiger

2722000415

$94.39 free shipping http://www.importecwarehouse.com/Mer...-04-15-wah.htm
$96.92 free shipping http://www.rmeuropean.com/Part-Numbe..._91DEFFEE.aspx
$98.86 free shipping http://www.autohausaz.com/search/pro...ber=2722000415

konigstiger

deleted

selina_mirza

Question: Dealer wants to charge me $632.00 to put in a new thermostat for my 2010 E350 Sedan. I can buy the part for about $100-$150. How difficult is it to replace the thermostat? Help please.

PurpleS500

thanks for the part number as was searching this thread came up, couldn't find the Sensor part number so can change both at the same time, any direction on helping me on that part number?
thanks in advanced

konigstiger

Thermostat 2722000415
http://workshop-manuals.com/mercedes...tat/page_6983/ (page down)

Sensor 0009050600
http://workshop-manuals.com/mercedes...ion/page_6967/ (page down)

PurpleS500

Thank You - konigstiger

ml3204me

Step by step Hi-Res Video show step by step how to do everything including draining the coolant as well as the P0128 error code.

http://mercedesrepairs.blogspot.com/...placement.html

giant330ci

I had the same error code p0128, so I did replace the thermostat today, but the check engine light is still on and the code is still there. Do I need to reset or will it disappear by itself? If I do need to reset, how? Thanks in advanced

foldhero

You only need to clear the code by your code scanner. No reset. I had changed mine and it solve the problem.

thunderbirl

I've just gone through the P0128 dance with my W211.

I used a cheapo infrared thermometer to read the temperature on the lower portion of the thermostat housing and confirmed the reading on the dashboard. This told me that the reading was correct and that the problem must be the thermostat. (i.e., it wasn't the computer reading it wrong!)

On Friday morning I called the dealer and found that they wanted $187 for the part (plus 8% tax). I ordered the Whaler OEM 483 4100D from Amazon AND had it shipped overnight, had the part by noon AND still saved over $100.

I did a lot of reading and, in the end, that was both good and bad.

To drain the system, you need only remove the front-most of the three underpanels. Don't get trapped into needing to find the block drain under the additional lower panels. I looked on my 4Matic and couldn't find it.

Get a short length of 5/16 hose and it will slip over the nipple on the lower rear left side of the radiator. There is a red screw which is (kinda) like a faucet valve. Open the screw and be ready to capture the 6 quarts of liquid that will, very politely, come out of the hose. (Don't forget to remove the cap from the reservoir!)

I looked at a variety of videos showing the actual change of parts. IMO, the best was . Although it's not specific for our model, it's absolutely identical to my 2008. The best parts are that he describes the tools needed and how to disassemble the electrical connector. It's very easy to release that connector, even while still on the engine. A minor weakness in the video is that the tensioner bolt (a 17 mm hex) is actually visually obscured from view. It's BELOW the belt. Don't talk yourself into removing the T40 bolt that holds the pulley in place on the movable arm. Also, FWIW, you don't "need" to remove the AIR pump if your sockets will reach the upper bolt. Removing the upper radiator hose is very easy after you properly position the locking clip - look at the new thermostat unit to figure this out.

To refill the system, you need only tighten up the red screw, remove the hose and pour the fluid back into the coolant reservoir. The system does a fantastic job at purging itself.

This is really a pretty easy repair.

My gauge temp went to 90C +/- 1 display segment.

In the middle of this, I also did a couple simple water flushes of the system - in part because I couldn't get to the block drain and in part because the antifreeze was 8 yrs old. (There are a bunch of threads about 15 year change intervals as marketing and packets of silica in the reservoir. I'm calling shenanigans on the latter!) Each time I drained, I could get about about 60% of the fluid out. If I've done my math right, after three flushes I'd removed about 93 or 94% of the original coolant. I then added a bit over six quarts of undiluted Zerex G-05 to the system and all seems good.

rapidoxidation

What kind of water did you use for the flush? Distilled?

thunderbirl

As a chemist, I have access to Reverse Osmosis, distilled, and deionized water systems including "water for injection". I chose to use municipal water as it is very adequate to this task.

kajtek1

Isn't reverse osmosis and distillate totally different things?
I only hope you will not be next member coming here in summer with overheating problem.
Seems all members with such problems are using Zerex.

rapidoxidation

My limited understanding of cooling systems has me using nothing but distilled water with pure (Mercedes, for $35/gallon) antifreeze in a 50/50 mix. The possibility of minerals in tap water makes it worth the $0.90 per gallon for distilled. Radiator cores don't like minerals.

That said, I'm no chemist...

kajtek1

Will bring Plutoe with his comments again, but this is good point to repeat that for over 3 years I drove 606 engine with engine fan removed, while going into 114F weather.
I had to put new radiator shortly after car purchase and being religious about using MB coolant (MB of Oakland sells it for $19) and distillate water make the cooling performing so well that aux electric fan was more that was needed.
Used car for towing small trailer as well.

thunderbirl

RO, distillation and deionization are all processes by which non-water molecules can be removed from the municipal water stream. Depending on how these processes are managed and the quality of the starting water, there may be some improvements regarding specific contaminants.

You can always use the readily available distilled water from the super-market. It'll add a few dollars to your change.

I don't know what water the MB dealers use.

I'll offer that, municipal water is certified to EPA standards. If yours is "relatively soft" - as mine is, you can use it without any additional purification.

I'll leave it to you as to what water to use as part of a flush...

As to "purity" of MB antifreeze.... I don't buy into the marketing and branding. Zerex is fully certified by MB for use in their vehicles. If spending the extra $30 for a change with MB branded blue goop makes you feel better than what you'd pay for golden, yellow goop - go for it.

As to driving without a fan and attributing the lack of failure to the use of distilled water, I'd like to point out that you have no controls in your experiment. You're attributing the lack of failure to something other than a magnificently over-engineered cooling system. Please note that 114F is well below the 194F regulated by thermostats. I see lots of room for cooling.

From a technical point of view regarding the influence of water purity on cooling in a typical 50/50 water/glycol system, the high contact angle for pure water on aluminum (look it up!) suggests that there could be significant improvement in contact, and maybe in cooling as well, from a functional surfactant - which is readily provided in the anti-freeze. It's well known that a really small amount of surfactant will cause a large decrease in contact angle and may contribute to potentially better cooling. It's also widely known that impurities in a solvent will reduce the contact angle - thus suggesting that trace contaminants from the water in a 50/50 glycol mixture aren't going to have a negative impact on cooling.

Again, no problem with using distilled water to dilute your antifreeze - but don't expect me to adopt your fears...

cmriv

Bitter cause I need to do this repair on my car... #Weaksauce