XSeries-forum

Your symptoms still sound like a thermostat open no matter how unlikely that is especially after fitting a new one. I am assuming that it was bled after the coolant refill. My only suggestion is to get one of those temperature guns and measure the temp of the top coolant hose going to the radiator as near the block as possible and that should be in the 90+c as it goes to get cooled in the rad. If you get a similar reading to your OBC then it's a dodgy thermostat no matter how unlikely.

Yes it does sound like that, but ......... since the new thermostat went in, the cabin heater is nice and toasty yet the sensor tells me the water is 58-60c, which bring me back to the sensor ......?

Smee

Not being a diesel owner and so not overly familiar with the positioning of sensors I went on Real OEM and had a look for the temperature sensor. Couldn't find any reference to it at all which makes me think it may be incorporated within the thermostat housing. Is there any wires/plugs that connect to the housing. Other than checking the temp' as previously suggested you'll have to wait on someone who is more familiar with this diesel engine.

Thanks for doing that Henry

Smee

Thinking it about it further, there must be some kind of coolant temperature sensor to give the data to the hidden menu ???

Update - ran the car idling on the drive for 30 mins. Hidden menu said temp was 40c. Switched off, opened rad cap. Coolant was lukewarn to the touch. Put cap back on and ran the car a few miles. Max temp reached was 60c
Smee

Sounds like the stat is wide open.

Indeed. But a brand new one?
Daft question - can they go in the wrong way round so they open rather close and vice versa?

Things can be DOA.  Manufacturers only batch test and it is possible that the installer messed up and damaged it too.

Ah ok !

Latest update. The garage who fitted the thermostat agreed it was running cold and agreed to replace it. They fitted a new one this morning which was still running on the cold side, idling at around 66c. They said they had done their own research and had learned that ECP/Andrew page supplied thermostats can be problematic for these cars. They have offered to fit a BMW one of Im not happy with no labour charge and I will pay the difference between that and the cheaper one. I took it for a run down the motorway for about 40 mins and the highest temp I saw was around 76c, so I've gone back and they have placed the order for the BMW one.

Will continue to update.

You've probably made a good decision. I hope so.

Ok. So mine goes in on Thursday. The garage is a bit swamped and so is only able to diagnose first rather than take my word that it is definately the thermostat. Not that I would know if it was anything else. He suggested that it was possibly quite a big job if indeed it was the thermo.
Anyone else know what ball park figure I'm looking at?
Is it fan out, drain coolant, replace thermo, refill etc?

Just had mine done this morning and now running at 90/91 on the dual carriageway  .
Got to the garage at 9am car went on the ramp about 9.10am and i was driving away at 10.30.
Can't say what the price would be as i get m8s rates and i paid £20 labour bought the part myself.
Just a note it only lost about 3 ltr of coolant.

Was that a BMW stat or aftermarket. Good result lets hope Smee is equally successful.