Technical Water temparature gauge on 150hp multijet

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Technical Water temparature gauge on 150hp multijet

I would imagine its noticable especially if trips are over 10 mins when engine up to temp, shorter trips probably not noticable as not much time at 90deg anyway.
Internal engine friction is higher at lower temps by approx 3-4nm which doesnt sound much but maybe around 7%
If it was nearer 60c it could be more like 15% more friction loss at 2000revs
Im not saying you will see mpg rise by this much but from what ive seen on similar threads you shoul see a few mpg rise instantly.
 
Huh if I knew that I would've done it sooner - I don't care that much for mpg as this engine is very kind to my style of driving, but that engine friction part I don't like.
It seems that the thermostat wasn't working properly ever since i bought the car last July, but it got gradually worse - at first the needle dipped just a little in cold weather and now it came down for a notch. Thankfully it didn't run lower than around 71 as I've checked it with FES when the needle was in it's lowest position.
The funny thing is, and I don't know if it's just coincidence, but the most noticeable drop in overall position of the needle occurred right after I've changed the coolant.
 
You did coolant change, before thermostat and it ran cooler?
Most probably with brand new coolant and possibly a flush of internal surfaces it was cooling more efficiently so with passing thermostat you actually made worse?
Sorted now anyway, was it easyish to do and bleed any bubbles?
You will feel the benefit soon when cold weather arrives id imagine it will warm up a fair bit quicker.
 
Yep that's right, after coolant change and before I did the thermostat it started running a bit cooler.
But I think it didn't take any longer to warm up - if I understand this thermostat correctly, I would say when the car got cold (ie overnight) it shut completely and until it got the signal to open it was closed - hence the car warmed up quickly. That's also why the needle went all the way up after you started a cold car. Then, after it opened for the first time, it couldn't move properly to keep the engine at the correct temperature - I'm guessing that big spring inside the thermostat gets worn after time.

As far as the actually changing it, it's not hard to do but it's extremely fiddlish. The main bolts are hidden so you have to feel them up like a girl in the dark, and there's also very little room for tools - but I did it and I'm far from a mechanic, so it shouldn't be a problem for you. You need to take out the battery, battery tray and the computer. And don't forget to buy enough jubilee clips (watch out for sizes as every hose is different in diameter I think).

After I changed the thermostat I opened the radiator bleed valve and the one on the hard pipe infront of the engine and poured in coolant until it came from the holes. Then I topped up the coolant and started the car without the expansion tank cap. Waited until the thermostat opened and then set the heating to highest setting so the coolant went into those hoses also.
Closed the expansion tank cap, idled it some more, waited for the car to cool halfway and opened the expansion tank again, for any remaining air to escape.
Then I went for a drive and opened the expansion tank again with car half warm. Added just a little coolant next morning when the car was cold - I hope that got all the air out.
 
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