A call from my GF's son on Halloween from 100 miles away in San Diego telling us that the "temperature spiked", and it overheated.
Played safe, and had it towed home.
Maybe its connected wiith him telling me with glee that he noticed that it has a steering shake at 85 mph...
I lent it him cos its slow, and gets great gas mileage thinking he would respect it...
If it was my boy I would have wiped the grin off his face...

Anyway, an investigation showed a coolant stream from the waterpump weep hole, and also a slight drip from the side of the radiator.
So, new Nissans radiator, a new water pump, gasket, thermostat, Zerex Coolant and Distilled water are on hand now.
The bill for the parts is close to $400, so the GF is paying...

Ever since I have owned this 190D I noticed that the temp gauge is very odd. It takes a long time to reach 80degC and it seems to follow the ambient temp rather than stay constant. I think the Thermostat is either stuck open or missing.

While I have it in my charge I am gonna change the oil and fuel filters and hope that the overheating didnt damage anything else.

Anyone have any input or suggestions on the revamp?
Should I backflush the heater core or replace anything else?

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2009 Mercedes ML320 Bluetec

Deep into it now!
Thermostat was there, and sitting in the closed position, but upon closer inspection and comparing it to the new one and the manual its not the correct one, AND the seal was missing/incorrect too... Result: Thermostat housing is corroded, and has a pin hole in the lower edge.
I cleaned it up and filled the hole and rebuilt the mounting flange with JB Weld steel mix. If this does not do it I will get a new housing.
Waiting for it to set now....

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2009 Mercedes ML320 Bluetec

Ok, all put together, but the coolant is not circulating....
Engine hot, Top hose hot, Electric fan coming on, radiator and bottom hose cold...
New Thermostat stuck closed?

Also the red topped sesor that is block mounted on the lower exhaust side broke off....
Fast Lane only lists a 3 pin type, and mine is a single pin...
http://catalog.peachparts.com/ShopByVehicle.epc?q=&yearid=1984@@1984&makeid=63@@MERCEDES+BENZ@@X&modelid=6119%3AED%7C10000092%3AMBC%7C1481@@190D&catid=240909@@Cooling+System&subcatid=241011@@Engine+Temp%2E+Sensor&applicationid=W0133-1627239@@Engine Temp. Sensor&mode=PA

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2009 Mercedes ML320 Bluetec

"not circulating"...?

you mean its not cooling?


did you put the spring side of the t-stat to the block?

Yes, the Thermo will only go in one way in fact.
It does not feel like its circulating thru radiator. Overflow was hot, top hose hot, but top of radiator and bottom hose was cool, even when the electric fan kicked in. As I edited above, I broke the top off the red sensor close to the water pump. I think its the fan clutch switch, so the engine fan is not engaging.
Anyone ever put a new thermostat in that was a Dud?

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2009 Mercedes ML320 Bluetec

the bottom hose should be pretty cool, not cold though.

That red switch on top of the head is for the electric fan clutch, your main cooling fan. The one they sell now has 3 prongs, but you just use the 2 you need.




if you pump the top hose a few times you should hear ticking, this the t-stat bouncing around and it is open if it is ticking.

The red topped sensor I am talking about is on the exhaust side of the block, just above and rearward of the Waterpump... I think it controls the electro-magnetic coupling for the engine driven fan on the 2.2D. The read cap snapped of the body of the sensor, and I think its toast. The temp gauge is working fine, and I think that sensor is in the head..
I will take a pic and post it in a few mins...

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2009 Mercedes ML320 Bluetec

Ok, seems to be working ok.
I took it for a drive and temp was stable around 90degC(Ambient is 80F)...
Is that "Normal"?
Radiator top is hot and bottom hose is warm.
After some fidding, I find that the temp sensor seems to control the Electric fan. Not sure if it does the mech too.

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2009 Mercedes ML320 Bluetec

it does not control the main fan on the water pump. There is another switch between the fuel filter and the head that controls that.

90* is fine. The fan clutch does not engage until after that... more like 98*. Congrats.

where do you live that 80* is ambient?.... very jealous over here!

Good!
Southern California baby!
Trust me, as a displaced Brit, I dont miss the cold and damp!

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2009 Mercedes ML320 Bluetec

The sensor that I broke seems to controls the high speed mode of the Electric Aux fan.

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2009 Mercedes ML320 Bluetec

Interesting. Thanks for figuring that out, I couldn't. I don't think the later model engines have it.