Hi guys,

I have recently added a temperature sensor Acewell ACE-TES M10x1mm thread temperature sensor on the draining plug underneath next to the water pump, which works perfectly and fits perfectly from what I can tell from the way it screws in. I have fit it with a copper washer as that is what usually goes into these sort of things.



https://www.acewell.co.uk/Acewell%20Accessories%20and%20Sensors/Temperature%20Sensors/ACE-TES.htm?action=full&id=32


Although, after a day or two I've noticed it does leak a few drops a day and it seems to be getting slightly worst by the day. I really don't think I can tight it up any more, as it can break (I've broken a sensor like this before).



I am very hesitant to simply put an o-ring, as this sensor gets pretty hot as normal working temperature of 70C up to around 100C.



Can anyone advise me on this, or did you have a solution for the same problem yourselves?


Many thanks and apologies for the silly question,
Paulo

Personally i would use a  copper crush washer or Dowty  or aluminium washer, all give a better seal than a plane copper one.

As can be seen from the attached photos, there are significant differences between your aftermarket sensor and the OEM—mainly the length of sensor and the position of its threads. It's good that you didn't attempt to tighten it more. Compare the length of the OEM to the aftermarket version. How much of the aftermarket threads are actually engaged? How long is it from the bottom of the nut to the tip of the sensor?

Using aftermarket sensors in this application seems to have been problematic. Maybe someone who has used one successfully that looked like yours will chime in. If its length isn't obstructing flow too much—or preventing tightening—and a crush washer won't stop the leak, maybe a Viton washer or two will.

OEM.


ACEWELL

I think I would be measuring up that shank above the treads and getting an o-ring to fill the space. At a guess say a 12mm OD by 8mm ID?
Most any o-ring will take coolant temperatures but there are high temp materials as well.
Something like this might work well

https://www.mcmaster.com/high-temperature-o-rings/square-profile-high-temperature-silicone-o-rings/

Hi,

You raise a very good point Laitch, I broke that other sensor for two reasons, one that it was bigger than the space inside the pump and the other reason was that the screw was Japanese or whatever it's called so it didn't fit properly. So yes I am aware many after market sensors don't fit!
I did measure it and the sensor is around 14mm long and the space inside is around 27 mm, so this sensor is good to use!

I went to my local shop this morning and they didn't have copper crush washer nor had a o-ring for high temperatures so I've taken a Dowty washer.

Good news! I went for a short ride, enough to get the temperature up to around 70C and now got cold and no leaks! Let's hope it will hold. Tomorrow I will go for a proper long ride!

Believe it or not I wasn't aware of those options, so many thanks for your answers!

Ha! Beat me to it. I was going to say 'use a Dowty washer'.