expectMerc

SO I got the engine light turned on the other day. Took it to autozone for a quick diagnostic and got P128 code (Thermostat/coolant related). My car is due for 60K service and I am planning to take it to the dealer in a week or so. The dealer recommended battery change (it failed the test) during the last service but I skipped it as the car was running fine.

I have read in this or other forums that code sometimes come up because of low battery so I will ask the service gut to replace the battery first to see if it goes away. How prevalent is that ?

Are there signs I need to check for if something is really wrong with thermostat ? Any temperature readings. I see that the temperature hovers around 80 +- 1 small bar. Is that an indication that the thermostat is fine. Can I drive the car safely for say a week with this light on/condition ?

Colin G

Is your car blowing cold air when the heat is on?


Could be a bad thermostat.

white46

I guess the thermostat fails around 60k miles or 100k kms mark as mine triggered CEL with P0128 as well.
Already bought the Wahler thermostat and MB coolant and will be working on over this weekend.

You can still drive the car, it may not run as efficiently, maybe reduced heat, but it's not major that need to be fixed asap.

expectMerc

Thanks. The dealer is trying to be stealer on this one and quoted me "$800" for this one claiming the part is $300 and labor is for 3 hours. I do not believe either as the part is $150 to $200 and looking at the video it should not take that long at all.

I called two independent shops. One of them do all kind of cars including all german with very good review. They quoted me $250 with OEM parts ( I am assuming they use Wahler) while the other $450 (they use Mercedes parts and told me the price for parts and coolants is ~$200 and the rest is labor. They supposedly do a better cleaning job which prevents the squeaking).

As you could guess by now, I am not comfortable doing it on my own. I do not have a garage anyways. I am going to first try the battery replacement route and if it does not go aways go with a independent shop. What should be a reasonable labor time for this one for people who do this for a living ?

white46

I bought whaler thermostat and MB coolant from fcpeuro for about $100 total.

As for labor, I will say 2hrs max.

Carsy

Have the battery load tested by an independent.auto electrician.

What is the point of changing out the battery if is perfectly OK?. It is only 5 years old.

Mine in 9 & still OK. Some achieve over 10 years service life.

My thermostat started controlling at 80'C. I changed it with a Wahler. A$182.Now back to 90'C ( Diesel).

95_993

My thermostat failed at about 38k miles. Had the dealer change it ...about $600. Yes, it's a rip off. I will change it next time