Engine coolant problems

1. sulgravesax L-plater Joined: Oct 2014 Posts: 42

   #1 8th November 2014, 21:22

   Hi guys
   
   I've got a problem with my 2001 vtr. The engine is getting hot but the temperature gauge is stuck on cold. The pipes from the top of the radiator and the heater matrix are hot but the pipe at the bottom which goes back into the expansion tank is stone cold. I have just replaced the temperature sensor but to no avail. If I unplug the sensor the temperature gauge goes up, the red light comes on and the fan cuts in. Once I plug the sensor back in the gauge goes back down to bottom and the fan stops.
   
   The plug for the sensor only has 2 wires with a another one that looks like it's been cut off. There are no other wires in the loom so I'm assuming it must have ever had only 2 wires. I can't work it out and it's starting to bug me.
   
   Any ideas?
2. user_64763 Established Member Joined: Jun 2013 York Posts: 2134 Citroen Saxo VTR (2001)

   #2 8th November 2014, 21:37

   The pipe at the bottom should be cold. Yes the sensor should only has 2 wires but with a 3rd that looks cut. It could just be the sensor itself that needs replacing! The gauge on the dials obviously works from when you unplug it but it's just not getting a signal so I'd say the sensor itself!
   
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3. sulgravesax L-plater Joined: Oct 2014 Posts: 42

   #3 8th November 2014, 22:49

   I've already replaced the sensor with a new one but I've just read that there's 2 sensors. One that feeds the ecu and one that feeds the dials?
4. oxass Infrequent Poster Joined: Sep 2014 Posts: 215

   #4 9th November 2014, 06:44

   The sensor in the thermostat housing sends a signal to the ecu.
   The sensor screwed into the head sends a.signal to the temp guage.
   The sensor can be tested with a multimeter.
5. sulgravesax L-plater Joined: Oct 2014 Posts: 42

   #5 9th November 2014, 10:54

   Surely the hose that goes into the bottom of the rad would be be hot? The water comes out of the engine hot then into the expansion tank, then through the radiator which is where the water is cooled then back into the engine to draw the heat out of the block again.
6. user_64763 Established Member Joined: Jun 2013 York Posts: 2134 Citroen Saxo VTR (2001)

   #6 9th November 2014, 12:02

   Quote:

   Originally Posted by sulgravesax Surely the hose that goes into the bottom of the rad would be be hot? The water comes out of the engine hot then into the expansion tank, then through the radiator which is where the water is cooled then back into the engine to draw the heat out of the block again.

   You've got it in reverse...the water doesn't go from the bottom of the expansion tank to the top lol
   The bottom hose is where the water leaves the expansion tank into the engine so by the time the water has got there it'll have passed through the radiator so it should be fairly cool.
   The top hose on the right of the rad will be the hot one but it'll only be hot if the thermostat has opened
   
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7. sulgravesax L-plater Joined: Oct 2014 Posts: 42

   #7 10th November 2014, 15:38

   ah that's why its cold then. most of the time im working in reverse so its not surprising lol. many thanks Jbrady for the clarification. ive got another sensor now so will try that tonight and see how we get on.

   1 user thanked this post: user_64763
8. user_64763 Established Member Joined: Jun 2013 York Posts: 2134 Citroen Saxo VTR (2001)

   #8 10th November 2014, 16:00

   Quote:

   Originally Posted by sulgravesax ah that's why its cold then. most of the time im working in reverse so its not surprising lol. many thanks Jbrady for the clarification. ive got another sensor now so will try that tonight and see how we get on.

   
   You owe me £15 for my service...
   
   
   Sent from my iPhone using Tapatalk
9. sulgravesax L-plater Joined: Oct 2014 Posts: 42

   #9 11th November 2014, 07:57

   i will send it in the post, is your address on dream street?