yet another w163 thermostat query

[big_amg]

Hi guys

Recently bought a 2003 ml270 cdi. I noticed the fuel consumption to be quite bad approximately 20/21 mpg (all inner London driving, short journeys) and also the engine temp usually around 60 to 70 degrees. Only goes above 80 in slow moving traffic but drops again on the move. Having read hundreds of thermostat threads, I can't find any who have had similar symptoms as in temperature going up in traffic hence the need to clarify. I don't want to spend 50 odd quid replacing something that's fine.

Any ideas?

 

[donubenz]

That's exactly what you expect. A thermostat holds the water in the engine block then opens progressively to allow the coolant reserve in the rad to flow and controls the temperature to the set point(92 degrees). If the stat is open all the water in the system circulates and gradually heats up. In traffic you are not getting forced air in the rad so it creeps up, once on the move the air ram effect cools it. You need a new stat to hold back the cooling fluid in the engine so it heats up to the controlled operating temperature.
Don

 

[Stratman]

One hundred percent faulty thermostat. You have described the classic symptoms.

 

[big_amg]

That'll be a challenge for me then! Fed up of paying labour charges. Hopefully it's not too hard a job

 

[grumpyoldgit]

This link is to changing a C270 CDI stat, but I would think it's the same engine in the ML270.
http://www.mbclub.co.uk/forums/engi...03-c-class.html?highlight=changing+thermostat
I changed mine a while ago and whilst doing it I also did an engine oil and filter change as access to the stat is much easier with the filter removed. One thing I didn't have, which in hindsight I wish I had, was a filter wrench. Although do-able by hand, it would have been much easier with a wrench, which I have now bought for next filter change. (Remember the filter housing is plastic and reusable, so if you decide to buy one, count the segments/flats around the edge and measure across the diameter, only a few £'s on fleabay). I also replaced the coolant as I didn't know how long it had been in.

Be careful with the plastic fuel lines as they harden and become brittle over time.

 

[joecash]

if u change the thermostat you will notice an improvement in mpg - could pay for itself within a couple of months depending on your mileage

 

[jacpriest69]

My ML270 sits at 60 to 70c. I have replaced the thermostat this weekend and its still sitting at 60c!! I have read that there is a thermostat fitted to the transmission oil cooler? Is it possible that this is stuck open and not allowing the engine to get up to the right temperature?

 

[BlackC55]

Is the gauge correct on the instrument cluster? There is no thermostat on the gearbox oil cooler.

Is the water pump working ok?

 

[c5jganno]

there is also a circulation pump mounted on the body next to the battery aswell,