Timewarpone

After driving for several miles my check engine light came on. I have an OBD2 Reader and code number PO128 was the only one thrown. The description in the manual states " Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature". No leaks detected, no overheating. The dashboard temperature reading is at 60 to 80 where it has always been. Does this possibly mean it is time to change the thermostat? or something else?

Rudeney

Yep, replace the thermostat.

Timewarpone

I was doing some research on parts associated with the thermostat and I came up with "Coolant Temp Sensor" which reads the temp of the coolant from the engine block. Might this need to be changed also? Also what type or brand of anti freeze should I get? Thanks in advance.

Rudeney

According to SDS/WIS, that particular code is a bad thermostat.

Timewarpone

I will change the thermostat. It makes sense. It is probably not opening as it should. Since I am going to change it I will flush out the radiator also. Does it matter what antifreeze I use and how much? Is 50/50 concentration recommended?

ALFAitalia

....or more likely not shutting fully as it should be running around 90 rather than the 60-80 you say yours runs at. I had the same problem.....but with no code. New stat and she runs smack in the middle of the gauge (or one block above). Gas mileage improved a little too.

Rudeney

Use the proper coolant, one that meets MB spec 325.0, 325.2, or 325.3. YOu can find the brands here:

http://bevo.mercedes-benz.com/bevolisten/325.0_en.html

Unless it comes pre-mixed, you will want to mix it 50/50 with distilled water.

Timewarpone

Zerez G 05 is on the list. This is sold locally for about $18 a gallon undiluted. Last evening I ordered a genuine Mercedes thermostat with gasket for my car. Cost me about $38 from parts.com it should be here in about 5 working days

Rudeney

Yes, G 05 is what I have used. I think I even bought the thermostat for my M112 engine in the C240 from Advance Auto - they had it in stock.

Timewarpone

Hello again, without driving the car I used my OBD2 Car Reader and another code is present PO715 "Input/Turbine Speed Sensor Circuit Malfunction" What does this do and what might I do about it? I am still waiting fot the Thermostat. Thanks

insame1

Ouch that is the conductor plate code. I would have your car checked with star and look for low voltage codes before I would replace it.

Timewarpone

There is no one local with the STAR. I would have to drive the car 45 minutes to my dealer. If I do need a conductor plate, which I am willing to do, how hard is it to replace? I did some quick shopping on-line and I found one for $156 at OSCARO.com The description states that it is an easy install but I have never done this before. Does the coductor plate go inside the tranmission where you would do a transmission fluid & filter change? I saw this on ebay for an OEM conductor plate but it also includes parts for a filter change also. I just had the transmission serviced by the dealer about 6 months ago which included changing the 13-pin connector.

http://www.ebay.com/itm/Mercedes-Tra...=mtr#vi-ilComp

Rudeney

Your car has the 722.6 5-speed, so the conductor place is a DIY (no SCN coding needed). You drop the transmission pan and filter, remove the electrical connector, some bolts, and the valve body with conductor plate comes out. At the bench, you separate them and replace the conductor plate. I'd say it's about a 7 on the DIY difficulty scale.

Timewarpone

When you stated "No SCN Coding Needed" does that mean I don't have to have the transmission codes reset with the "STAR" after I change the conductor plate ? Thanks

insame1

My C32 absolutely need the codes cleared to come out of limp mode and my scanner could not clear the TCU codes. Had them cleared at my indy and the car ran fine. That being said I had it replaced on my 55 at a different indy and they showed me the MB document saying it needed coded and there is a procedure of stops starts and shifting that is recommended after replacement.

Timewarpone

At the moment the car is in the garage. I don't know if it is in limp mode or not. I can drive it locally but the shifting is funny. The tranny does not respond the way it used to. I saw an excellent YouTube video yesterday on how to change the conductor plate for my transmission. I am all for doing it myself. My problem is resetting the transmission codes if need be.

Rudeney

SCN = Software Calibration Number, which is code that locks the part to the VIN, and this can only be done with a "live" SDS setup that communicates with MBZ corporate. On the 722.6, this is NOT needed, but on the 722.9 it IS REQUIRED. As for error codes, yes, you may need to clear codes from the TCU, and most generic OBDII scanners won't do that, but it does not require SDS. Others good tools like iCarsoft i980 and the Snap-On system many indy shops use can do that.

Timewarpone

If I buy a iCarsoft i980 scanner then I will be able to diagnose my CLK320 and then clear the transmission codes after I replace the conductor plate? Thanks

Rudeney

It won't change the coding - you need SDS for that - but otherwise it scans and resets codes on all the car's systems: ECU, TCU, SRS, ESP, SAMs, ACC, etc.

Timewarpone

Pardon my ignorance, but what is SDS? Thanks

Rudeney

SDS = Star Diagnosis System, MBZ's system that the dealers use. You can actually get a "clone" this for yourself from China. A turnkey system will cost around $500, or if you are very computer savvy, you can piece it together for as little as $250. It's very powerful, maybe too powerful for the casual shade tree mechanic, but it does everything the dealer can do (and more as "developer mode" is activated in the clones).

Timewarpone

I changed the thermostat yesterday with a genuine replacement part with good results. It cleared the PO128 code I was getting but the PO715 code is still present. The dealer gave me a quote yesterday for $1500 to do the conductor plate. I finally found a local repair shop, 25 miles from where I live, that regularly services BMW's and Mercedes and was quoted $700 for the exact same thing the dealer was going to do. They are even giving me a 1 year 12,000 mile warranty on the repair. If I buy everthing myself including a i980 scanner, ATF fluid, filter, gasket and conductor plate with 13 pin connector, all genuine MB parts, my cost to do it myself is around $360. On another note - I really don't know if the car is in limp mode or not. I test drove it yesterday after I did the thermostat and the shifting is still acting real funny but I didn't go over 5 MPH. The dealer told me over the phone that to get it out of limp mode is to shut off the car, remove the key and then start it again.

Rudeney

In that case, I'd buy the scanner and check TCU codes before spending any more money on it.

Timewarpone

I was leaning towards buying the scanner anyways. It is a keeper for future use. I got a brand new one from Ebay: http://www.ebay.com/itm/331913314943?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Timewarpone

I received my i980 today. The very first thing I did was to update it online. Two fault codes were detected.

1.)Transmission - P2203: internal electrical check of component Y3/6 n3 (speed sensor 3) has failed.

2.) ME SFI2.8 - P2066-004, P2066-016, P2066-064 - NOx Sensor Circuit High Bank 1

No other codes were thrown. I even ran the OBD2 feature that is built in and it says PO715 "Input/Turbine Speed Sensor Circuit Malfunction" just the same as my other OBD2 Car Scanner did.