Temp sender location?
Temp sender location?
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AMG Merc

Original Poster:

11,955 posts

282 months

Monday 12th November 2007
quotequote all
Can someone remind me where it is please - a photo would be useful?

Also, if you lose some coolant would you expect the temp gauge to read high or are there any conditions where it could read normal.

art411y

832 posts

249 months

Monday 12th November 2007
quotequote all
which one ? the water temp sensor on the 2.5 is in line with the solenoid on the starter motor and is a 2 wire affair.the temp sender is a 1 wire i believe but without going out to the car i cannot remember were it is

AMG Merc

Original Poster:

11,955 posts

282 months

Monday 12th November 2007
quotequote all
art411y said:
which one ? the water temp sensor on the 2.5 is in line with the solenoid on the starter motor and is a 2 wire affair.the temp sender is a 1 wire i believe but without going out to the car i cannot remember were it is
Thanks, I meant whatever sender/sensor signals the water temp gauge?

joust

14,622 posts

288 months

Tuesday 13th November 2007
quotequote all
Apart from early MM 2.5's the ECU sends the temp to the dial.

J

AMG Merc

Original Poster:

11,955 posts

282 months

Tuesday 13th November 2007
quotequote all
joust said:
Apart from early MM 2.5's the ECU sends the temp to the dial.

J
Thanks Justin, so are you saying that there isn't a physical sender in a water pipe anywhere? So how does it read real water temp then?

joust

14,622 posts

288 months

Tuesday 13th November 2007
quotequote all
On my old 2.5 the actual sender was in the pipework to the radiator. Where it is in later cars I'm not sure - sorry.

J

georgeM400

732 posts

229 months

Tuesday 13th November 2007
quotequote all
AMG Merc said:
Can someone remind me where it is please - a photo would be useful?

Also, if you lose some coolant would you expect the temp gauge to read high or are there any conditions where it could read normal.
when i lost coolant on my M400, my temp stayed constantly at 90 degrees and did not read too hot/cold at anytime. feel around all the hose connections and see if there is any water anywhere.

AMG Merc

Original Poster:

11,955 posts

282 months

Tuesday 13th November 2007
quotequote all
georgeM400 said:
AMG Merc said:
Can someone remind me where it is please - a photo would be useful?

Also, if you lose some coolant would you expect the temp gauge to read high or are there any conditions where it could read normal.
when i lost coolant on my M400, my temp stayed constantly at 90 degrees and did not read too hot/cold at anytime. feel around all the hose connections and see if there is any water anywhere.
Thanks, that's my point - why donl't they place the sensor highup in the system so if any water is lost the reading goes instantly high.

JLSELAN

405 posts

262 months

Tuesday 13th November 2007
quotequote all
It is and it does.
The sensor is positioned near the thermostat on the 3.0s, which is located in the coolant line exiting the head (where the coolant is at its hottest).
AFAIK there is enough excess capacity in the cooling system that you would have to lose a significant amount of coolant before it was compromised. That said, it's always a good idea to keep an eye on the coolant level in the reservoir since that provides an early warning alarm for system leaks.
As for the relationship between the sensor, the ECU and the gauge: the ECU controls the gauge based on data it "sees" from the sensor because coolant temp is important to the choice of fuel/ignition map that the ECU uses for the motor. In older cars, the coolant temp sensor would usually be connected directly to the temp gauge, which is the way it's done for the Noble's oil temp sensor/gauge.

joust

14,622 posts

288 months

Tuesday 13th November 2007
quotequote all
The ECU has a 'flat' map between about 80 and 100, which means it sits at 90 most of the time. If it suddenly shoots up then that is the point to stop.

This isn't a Noble specific thing - pretty much all cars have done this for about 15 years. There is actually no difference in cooling between a Triumph Spitfire and, say, a BMW M3, it's just that in the spitfire the guage told the actual story - nowdays it's deemed more "acceptable" to stick it at 90 and hold it there all the time that things are "normal".

J

AMG Merc

Original Poster:

11,955 posts

282 months

Wednesday 14th November 2007
quotequote all
Thanks guys, that's interesting.