More data on fluctuating temp gauge... ??? (long)
10-21-2005, 05:04 AM
#1
AudiWorld Senior Member
Thread Starter
More data on fluctuating temp gauge... ??? (long)
Preface: maybe coincidence, but this started after I changed my grille from an LLTek to a new badgeless 5-bar, like Uneek has. Prior to this, gauge always went straight to 12:00, and fluctuated above that normally in traffic as the fans would cycle on and off.
This morning, as soon as I cranked 'er up, set the digital display for 49C, "coolant temp". Heater set "on" at 73 deg, low speed fan. Ambient outside displaying 52F.
Took off, down county road running about 45-50. Gauge and display tracked in sync, with gauge needle hitting 12:00 at 80C displayed. Noted the following things on the 35 mile run in:
~ twice, on the county road, I went through "cool spots" where the air is noticably colder, and the gauge dropped and the display went from about 81 down to 77 fairly quickly, then came back up to about 81C after I'd passed through the area. Oil temp about 150.
~ At Haymarket, sat at stoplight, and temp again dropped to about 78C. (No, the fans did not run)
~ Got on I-66, and ran 75mph for about 3 miles, then had to slow to about 45. Temp went from 83 back to 77 as soon as I slowed down to 45. Gradually came back up as we picked up speed to 60mph. Cruising, display never went over about 84C.
~ Noted this phenomenon once more when we slowed down near Rte 55.
~ Creeping in traffic for several miles, temp display went as high as 94C, but never higher as we kept moving slowly, getting air through the radiator. Oil temp was constant around 200F all this time.
~ After hard run in on 66 and Beltway, exited and stopped at a light for about 4 min. Idling, temp went about 93C, then started to come down slowly, even tho fans were not running.
~ Drove 2 more blocks and sat in parking garage idling. Temp got to 96C, still no fans, and stabilized before I shut it down.
QUESTIONS: I thought we had 90C thermostats? 80C is only 176F, and 94C is only 201.
If the thermo was 90C, it theoretically should not open fully until the coolant temp was to that level, so instead of running 75mph at 80F, I'd think I should be at 90(+).
I also thought that the thermostat would regulate the base temp (90C) once it opened. I don't ever recall, in my 50+ vehicles, having one that "cooled off" once the thermostat opened.
Can't imagine that the thermostat is opening more than it should, thus allowing more water flow/cooling.
Since oil temp tracks pretty well with the gauge/display (oil always being hotter), don't think there's an issue with the green temp sender (altho it could feed both the gauge and the display?)
Anyone else ever observe anything like this? Since I'm "over-cooling" rather than overheating, I'm not too worried, but I'd like to understand it.
Fig
Fig
This morning, as soon as I cranked 'er up, set the digital display for 49C, "coolant temp". Heater set "on" at 73 deg, low speed fan. Ambient outside displaying 52F.
Took off, down county road running about 45-50. Gauge and display tracked in sync, with gauge needle hitting 12:00 at 80C displayed. Noted the following things on the 35 mile run in:
~ twice, on the county road, I went through "cool spots" where the air is noticably colder, and the gauge dropped and the display went from about 81 down to 77 fairly quickly, then came back up to about 81C after I'd passed through the area. Oil temp about 150.
~ At Haymarket, sat at stoplight, and temp again dropped to about 78C. (No, the fans did not run)
~ Got on I-66, and ran 75mph for about 3 miles, then had to slow to about 45. Temp went from 83 back to 77 as soon as I slowed down to 45. Gradually came back up as we picked up speed to 60mph. Cruising, display never went over about 84C.
~ Noted this phenomenon once more when we slowed down near Rte 55.
~ Creeping in traffic for several miles, temp display went as high as 94C, but never higher as we kept moving slowly, getting air through the radiator. Oil temp was constant around 200F all this time.
~ After hard run in on 66 and Beltway, exited and stopped at a light for about 4 min. Idling, temp went about 93C, then started to come down slowly, even tho fans were not running.
~ Drove 2 more blocks and sat in parking garage idling. Temp got to 96C, still no fans, and stabilized before I shut it down.
QUESTIONS: I thought we had 90C thermostats? 80C is only 176F, and 94C is only 201.
If the thermo was 90C, it theoretically should not open fully until the coolant temp was to that level, so instead of running 75mph at 80F, I'd think I should be at 90(+).
I also thought that the thermostat would regulate the base temp (90C) once it opened. I don't ever recall, in my 50+ vehicles, having one that "cooled off" once the thermostat opened.
Can't imagine that the thermostat is opening more than it should, thus allowing more water flow/cooling.
Since oil temp tracks pretty well with the gauge/display (oil always being hotter), don't think there's an issue with the green temp sender (altho it could feed both the gauge and the display?)
Anyone else ever observe anything like this? Since I'm "over-cooling" rather than overheating, I'm not too worried, but I'd like to understand it.
Fig
Fig
10-21-2005, 05:12 AM
#2
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Well.>>>
your car runs nice and cool...i did 350 miles yesterday and my car ran from 94-105C....but i am running a Wahler thermostat, which i will change out soon for an OEM one....
When traveling on the highway, in 6th gear...there a heavier LOAD on the motor...so what you will see is the temps go up when accelerating in 6th quicker than say 5th. This is due mostly to the amount of stress put on the motor when the car requires HP to accelerate in 6th. Torque is the key in the lower gears.
So..if when you drive, you have a tendency to use more RPM's, there is less stress on the crankshaft in the motor.
I think what you are seeing is the LOAD changes generating heat and cooling based on your style....
Just my nickles worth! ;-)
Btw- nice meeting ya at H2O! ;-)
When traveling on the highway, in 6th gear...there a heavier LOAD on the motor...so what you will see is the temps go up when accelerating in 6th quicker than say 5th. This is due mostly to the amount of stress put on the motor when the car requires HP to accelerate in 6th. Torque is the key in the lower gears.
So..if when you drive, you have a tendency to use more RPM's, there is less stress on the crankshaft in the motor.
I think what you are seeing is the LOAD changes generating heat and cooling based on your style....
Just my nickles worth! ;-)
Btw- nice meeting ya at H2O! ;-)
10-21-2005, 05:16 AM
#3
Re: More data on fluctuating temp gauge... ??? (long)
it is normal for the low speed fans to kick on at about 97-100 F at idle and the temp will drop quickly down to about 89 F or so. The thermostat only does so much in regulating overall system temperature. The radiator fans are critical in this regard, esp at idle.
BTW, you do have an updated green engine coolant temp sensor, don't you?
BTW, you do have an updated green engine coolant temp sensor, don't you?
10-21-2005, 05:26 AM
#4
Re: More data on fluctuating temp gauge... ??? (long)
disregard my F's and substitute Celcius for the temps...I wish we in the USA could finally go metric and avoid brain farts like I just had!
10-21-2005, 05:30 AM
#5
AudiWorld Senior Member
Thread Starter
Thanks, Hans and Rocky
Yep, green sender.
What I don't understand is-- what's different from the last almost-4 yrs other than the grille?
Granted, it may be more efficient in directing airflow across the radiator, given the way the slats are layed out...
Fig
What I don't understand is-- what's different from the last almost-4 yrs other than the grille?
Granted, it may be more efficient in directing airflow across the radiator, given the way the slats are layed out...
Fig
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