Temperature Gauge Fluctuations
Thread Starter
Newbie
Joined: Mar 2017
Posts: 9
Likes: 1
s350
Temperature Gauge Fluctuations
**** Below is my Original Post*****
Hi
Yeah I understand all that and to some degree that is the same logic I have been trying to apply.
But I can punch a few holes in that...what after fitting a new collateral temp sensor did the temp guage say pretty solid at around 90 C for 10 days when I was driving the same route work and back. Any why did this problem only restart after i came down asteep hill goe a diatan e of about 1.5 miles. During that time the temp droppwd to 80 form about 90. So this evening on my home from work came through town traffic. Temp guage was cycling between 80 and 90 all the while is was dr8nv in town which was about 30 mins. I then hit the open road and the temp keeps cycling between 80 and 90...it took 3 cycles and a distance of about 8 miles before the car settled down and again became pretty rock solid at about 90....
could I still uave a small air lock...but if I did I would possibly expect it to cycle all the time.... does yhe system need a minimum distance to monitor the averages of temp before it settles down....is it as still as theses temp gauges are very sensitive.
I have had may cars over the years...BMW SAAB other Merc and none of these have had such a twitchy temp gauge and to add insult to injury I believe these electronic thermostats are supposed to be more steady than the old mechanical ones.
Does anyone know what signals feed the coolant temp gauge.
many thanks guys....
Hi
Yeah I understand all that and to some degree that is the same logic I have been trying to apply.
But I can punch a few holes in that...what after fitting a new collateral temp sensor did the temp guage say pretty solid at around 90 C for 10 days when I was driving the same route work and back. Any why did this problem only restart after i came down asteep hill goe a diatan e of about 1.5 miles. During that time the temp droppwd to 80 form about 90. So this evening on my home from work came through town traffic. Temp guage was cycling between 80 and 90 all the while is was dr8nv in town which was about 30 mins. I then hit the open road and the temp keeps cycling between 80 and 90...it took 3 cycles and a distance of about 8 miles before the car settled down and again became pretty rock solid at about 90....
could I still uave a small air lock...but if I did I would possibly expect it to cycle all the time.... does yhe system need a minimum distance to monitor the averages of temp before it settles down....is it as still as theses temp gauges are very sensitive.
I have had may cars over the years...BMW SAAB other Merc and none of these have had such a twitchy temp gauge and to add insult to injury I believe these electronic thermostats are supposed to be more steady than the old mechanical ones.
Does anyone know what signals feed the coolant temp gauge.
many thanks guys....
Thread Starter
Newbie
Joined: Mar 2017
Posts: 9
Likes: 1
s350
***Response from Plutoe****
You do not have a problem-stop and go village driving always increases engine coolant temp(less volumes of air moving through the rad)
__________________
XDOS\DAS\Vediamo\SCN coding in Tampa-Orlando-Daytona Beach Area
PS---Don't forget checking the prerequisites of: read your manual and look at-- wiring conditions, voltage, vacuum, fuses, relays and exhaust leaks before diagnosing faults!
You do not have a problem-stop and go village driving always increases engine coolant temp(less volumes of air moving through the rad)
__________________
XDOS\DAS\Vediamo\SCN coding in Tampa-Orlando-Daytona Beach Area
PS---Don't forget checking the prerequisites of: read your manual and look at-- wiring conditions, voltage, vacuum, fuses, relays and exhaust leaks before diagnosing faults!
Thread Starter
Newbie
Joined: Mar 2017
Posts: 9
Likes: 1
s350
**** My update and further questions from today 10th March****
Hi
Yeah I understand all that and to some degree that is the same logic I have been trying to apply.
But I can punch a few holes in that...what after fitting a new collateral temp sensor did the temp guage say pretty solid at around 90 C for 10 days when I was driving the same route work and back. Any why did this problem only restart after i came down asteep hill goe a diatan e of about 1.5 miles. During that time the temp droppwd to 80 form about 90. So this evening on my home from work came through town traffic. Temp guage was cycling between 80 and 90 all the while is was dr8nv in town which was about 30 mins. I then hit the open road and the temp keeps cycling between 80 and 90...it took 3 cycles and a distance of about 8 miles before the car settled down and again became pretty rock solid at about 90....
could I still uave a small air lock...but if I did I would possibly expect it to cycle all the time.... does yhe system need a minimum distance to monitor the averages of temp before it settles down....is it as still as theses temp gauges are very sensitive.
I have had may cars over the years...BMW SAAB other Merc and none of these have had such a twitchy temp gauge and to add insult to injury I believe these electronic thermostats are supposed to be more steady than the old mechanical ones.
Does anyone know what signals feed the coolant temp gauge.
many thanks guys....
Hi
Yeah I understand all that and to some degree that is the same logic I have been trying to apply.
But I can punch a few holes in that...what after fitting a new collateral temp sensor did the temp guage say pretty solid at around 90 C for 10 days when I was driving the same route work and back. Any why did this problem only restart after i came down asteep hill goe a diatan e of about 1.5 miles. During that time the temp droppwd to 80 form about 90. So this evening on my home from work came through town traffic. Temp guage was cycling between 80 and 90 all the while is was dr8nv in town which was about 30 mins. I then hit the open road and the temp keeps cycling between 80 and 90...it took 3 cycles and a distance of about 8 miles before the car settled down and again became pretty rock solid at about 90....
could I still uave a small air lock...but if I did I would possibly expect it to cycle all the time.... does yhe system need a minimum distance to monitor the averages of temp before it settles down....is it as still as theses temp gauges are very sensitive.
I have had may cars over the years...BMW SAAB other Merc and none of these have had such a twitchy temp gauge and to add insult to injury I believe these electronic thermostats are supposed to be more steady than the old mechanical ones.
Does anyone know what signals feed the coolant temp gauge.
many thanks guys....
Thread Starter
Newbie
Joined: Mar 2017
Posts: 9
Likes: 1
s350
Hi Guys
Does anyone have any insight into my temp guage fluctuations.
Eg...last night I drove home while I was on the open the car sat at about 90 degrees C.I was driving at about 60mph all the time. Then I stopped for about 10 mins and then went b on my way again. This from start the temp went from 90 to 80 to 90 to 80 and back up to 90 before I got home. This tool place over a 10 min period. While driving on a country road at speed between 40 to 50 mph.
I get that while the car was stopped for 10 mins the engine heated up but what I don't get is the amount of hunting that was going on worn the temp guage. I totally understand one cycle from 90 to 80 and back to 90 degrees. But what would the car do three cycles. I have read nearly every four to try and find an answer but as many people say this is normal operation as there is saying it is not. Does anyone fully underarms how the temp guage on the w221 works.....I have c read loads of information on this but can't seem to find a definite answer....sorry about the bad tying Im doing this from my phone.....any insight would be gratefully accepted
Does anyone have any insight into my temp guage fluctuations.
Eg...last night I drove home while I was on the open the car sat at about 90 degrees C.I was driving at about 60mph all the time. Then I stopped for about 10 mins and then went b on my way again. This from start the temp went from 90 to 80 to 90 to 80 and back up to 90 before I got home. This tool place over a 10 min period. While driving on a country road at speed between 40 to 50 mph.
I get that while the car was stopped for 10 mins the engine heated up but what I don't get is the amount of hunting that was going on worn the temp guage. I totally understand one cycle from 90 to 80 and back to 90 degrees. But what would the car do three cycles. I have read nearly every four to try and find an answer but as many people say this is normal operation as there is saying it is not. Does anyone fully underarms how the temp guage on the w221 works.....I have c read loads of information on this but can't seem to find a definite answer....sorry about the bad tying Im doing this from my phone.....any insight would be gratefully accepted
Junior Member
Joined: Nov 2011
Posts: 48
Likes: 5
2008 S550
Sounds like a sticky thermostat to me. The temp sensor is integrated in the housing on the thermostat. Kinda pricey though. Check it with hot water first to make sure it opens slowly and all the way before replacing. The opening temperature varies with age.
Temp fluctuations generally are from obstructions, air or cavitation in the pump from the air. The thermostat is an obstruction to let it reach operating temp. If it gets stuck half way when it reaches operating temp it will allow fluid to flow but the average temp will be higher. When it pops open all the way the temp will drop to norm. It opens and closes regulating the temp all the time to be at a constant temperature (with the help of your fans when it gets too hot and your not moving).
Air maybe? Bleeding is easy, just remove the radiator cap (when it's not hot) and let the car run at operating temp for a few minutes. Make sure it doesn't overflow. Then close it.
Temp fluctuations generally are from obstructions, air or cavitation in the pump from the air. The thermostat is an obstruction to let it reach operating temp. If it gets stuck half way when it reaches operating temp it will allow fluid to flow but the average temp will be higher. When it pops open all the way the temp will drop to norm. It opens and closes regulating the temp all the time to be at a constant temperature (with the help of your fans when it gets too hot and your not moving).
Air maybe? Bleeding is easy, just remove the radiator cap (when it's not hot) and let the car run at operating temp for a few minutes. Make sure it doesn't overflow. Then close it.
Thread Starter
Newbie
Joined: Mar 2017
Posts: 9
Likes: 1
s350
Hi Thanks for the response. I'm afaid it's not the therostat as that has been changed twice. Also the temp sensor on the back of the head and the Warter pump has been changed. The thermostat on these is an electronic one. So the two pins is not the temp sensor but power to the station. These stats operate as a older mechanical one but when required the ecu will independently control the status and send a signal to open it. I belive the gauge is controlled by one of modules on the car and what we see is not a direct reading but a reading supplied by one of the electronic modules and that is dependant of a number of different inputs to the module. I think it's the engine ecu that drives the temperature gauge... I have also bled the coolant a couple of times. I haven’t got much more to change other than the fan and that is quite expensive and don't want to do that until I have good evidence.
But first I'm trying to find out if this is normal. The big question for me is how much movement of the gauge should I expect to see under what driving conditions
But first I'm trying to find out if this is normal. The big question for me is how much movement of the gauge should I expect to see under what driving conditions
