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E550 P0128 code - Thermostat below temperature (problem resolved)
Incase anyone is looking, I was able to successfully debug and replace the thermostat in my E550. Not the best instructions but should be helpful. Images are marked with the steps below.
Had the check engine light come on and noticed that my needle was only at 50 or 60 degree temp which meant that thermostat was stuck open and cooling the engine. Also feeling the radiator hose on cold start, coolant would start to flow right away and pipe would be warm.
This was my issue and pics below you can see the difference in old versus new where the old part, valve is stuck open.
Steps to replace:
1) remove plastic covering
2) remove belt
3) remove bracket above the center pully
4) remove pully
5) remove both turbo pipes on the driver side
6) should have easy access to the thermostat now
7) unclip wiring
8) thick towels and drain pans under the car
9) unclip radiator hose, will need to twist a bit to get it to brake loose. I had to unclip the other side of the hose connected to the radiator to make it easy to twist. Pay close attention to how it came out as you will need to put it back and ensure it is secured. Otherwise will need to tow the car home later like I did My hose came off as it was not clipped back properly while driving.
10) loosen all the thermostat bolts and it should come out
11) reverse order in putting everything back
12) fill with coolant
13) start car and I did a reset with my scan tool but eventually light should go away once it detects everything is back to normal. Again not the best at documenting this but should help someone in future. Thanks Pic of the new thermostat Thermostat stuck open (top image) 2. Will find plenty of images online on how the belt goes back. Do inspect it and replace if needed. 3 4 5. Bottom bolt for the turbo pipe 5 7 9 9 9 10 10
Add the coolant to the reservoir and wait until gravity suck it to the radiator, if you want to speed up the operation you can squeeze the lower radiator hose until the radiator is full (also the reservoir) put the reservoir cap and run the car al little bit and check the coolant level next day.
Add the coolant to the reservoir and wait until gravity suck it to the radiator, if you want to speed up the operation you can squeeze the lower radiator hose until the radiator is full (also the reservoir) put the reservoir cap and run the car al little bit and check the coolant level next day.
Agree, I had the kit from my cousin but didn't end up needing it. Just filled it and let gravity do its thing.
Good writeup - thank you. I recently got the P0128 code in my 2012 E550 Coupe and can see that the engine isn't heating up like it should, so likely the thermostat stuck open.
How much time would this take? Any special tools I will need?
I'm comfortable changing brakes and oil. Is this something I should tackle?
You can only really get to it if your thermostat hose i@CaliBenzDriver pointed this out to me. It was about a $17 part if I remember correctly and the Mercedes dealership said they had a ton on hand.
You can only really get to it if your thermostat hose i@CaliBenzDriver pointed this out to me. It was about a $17 part if I remember correctly and the Mercedes dealership said they had a ton on hand.
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My hose came off as it was not clipped back properly while driving.
