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Discussion Starter #1
Just wondered where the majority of peoples temp needles sit. Mine used to sit within the "norm" on the gauge, lower end when cruising, and mid to high in traffic.

A couple of years ago I flushed my system and fitted a new thermostat, anti-freeze, and filled with distilled water. After that, the gauge sat much lower, just under the norm when cruising, and I seem to remember it took a long time when stationary for it to go up into the zone where the fan cut in.

My cars been laid up during the last year, I drove it yesterday, and noticed that it still sits fairly low when cruising, but when I sit in traffic or stop at the lights, it goes up to midway quite quickly, and goes right to the top end of norm before the fan cuts in. The fan does always cut in, and nothings bubbling/leaking

Just wondered if this is normal, or if I need to flush and change my stat again, or change my temp sensor?

By the time the engine is up to the mid point on the gauge, it feels like the stat is already open, as the top hose was hot. I had been on a run though. Maybe I should test to see when the stat opens, and the hose gets warm from cold. I haven't got access to any proper temp measuring equipment
 

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The temp gauges on these cars are rather unreliable and inconsistent. One gauge might read N at 200°F, another might read between O and R. That said... on my 94 the gauge would read just to the left of the N while cruising in cold temperatures, and ride right on the N cruising in warmer weather. It creeps up to O-R before the fan kicks on. My father-in-law's 97's gauge reads about 2/3 while cruising. My 97 would read about 1/2 at the same temperature.

As long as the fan comes on at the right temperature (verify using an IR thermometer at the coolant crossover near the t-stat), you're in good shape. Basically, each gauge has its own "personality". :)
 

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Thanks Brandon, I think mines doing pretty much what it always used to (before I put the new antifreeze in). It just seemed like the behaviour changed after it spent the year sitting around. Maybe the antifreeze has just "aged" a bit.
 

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While the gauge isn't very accurate in terms of consistency from one car to the next, it really shouldn't move around much at all once the vehicle is warmed up, short of beating on it in 100+ degree heat. Given that it heats up in traffic and cools down once moving, and that the fan is cycling, I would suspect an air bubble trapped somewhere.
 

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Discussion Starter #7
I'll have to go back through my receipts/emails and try and find out which thermostat I've got in there. I got it sent over by Jason 3 yrs ago when I did the heater core.
 

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Mine is still all original except for the water pump and it stays right in the middle. I do need a new radiator and plan to install a 180 degree stat at the same time.
 

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I've had a few different clusters and senders in my car and they all seem to hover just below the N, as it did when it was stock. I must be lucky when it comes to consistency :tongue:


Air bubbles make it dance all over the place
 

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There IS a pair of TSBs - older one-wire sending units would fail due to the internal design and read LOW. Later ones would fail and read HIGH.

Before I panic one way or the other, I'd a) query the ECU if at all possible (i.e., for an OBDII system) and see what the ECU is seeing, and b) consider replacing the sending unit.

RwP
 

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My temp. gauge sits right around the "r", and the "m". Have never really noticed it to move much. It does move a little depending on ambient temp., and load.
 

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Mine behaves nearly identical to the OP's. I have a 97 sport with factory 195* replacement. It's relatively normal (half way point) while cruising. If I'm sitting in traffic for a while, especially after I've been driving a while then it goes up around 3/4 of the way. I used to get a little worried but it never goes any higher and the fans kick on. I thought it was normal for these cars.
 

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Discussion Starter #13
Interesting seeing the way different cars behave.

Mine behaves nearly identical to the OP's. I have a 97 sport with factory 195* replacement. It's relatively normal (half way point) while cruising. If I'm sitting in traffic for a while, especially after I've been driving a while then it goes up around 3/4 of the way. I used to get a little worried but it never goes any higher and the fans kick on. I thought it was normal for these cars.
This sounds pretty much the same as mine. I feel better now! I think I'll see how it goes for a while, then if I'm not happy I'll flush it and fit another new thermostat.
 

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Does anyone else's temp gauge read significantly lower with the AC on? Mine takes at least 15 minutes of driving in traffic in 80 degree weather to reach N. When I'm moving at a steady speed it usually stays below the N and the fan never comes on. With the AC on it also gets below the N.
 

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Mine rarely moves above the "[" for [NORMAL] . That's with my stock replacement radiator DOHC swap with my super large trans cooler, Ford Zerex G-05 50/50 Gold Coolant and the Reinhardt 170 degree high flow DOHC thermostat. Keeps really cool even after hard racing at the track in 100+ degree heat. Also running a 93 mark viii fan and coolant inlet flow resistor in line to my heater core.
 

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Fully stock motor plus CAI, my needle runs just north of dead center in the summertime. Just south in the winter. No noticeable difference with A/C running.
 

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Mine (94) will run just left of the N (188-195)at night and while cruising around town, in the middle on the interstate below 70 mph (195-210), 75mph+ it runs on the R to just past the M (210-220). In the winter, no matter how hard I beat on it, it never got past 190. As I have seen it on here, these temp gages are as accurate as a sundial on a cloudy day.
 

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Forgot to mention even in the heat of the summer the coolant temp never sees above 200 degrees or the N in [ NORMAL ] in 110 degree summer heat, cruising, racing, highway, etc. I monitor my temp with a scan gauge II. I'm looking to add an oil cooler, larger radiator, aux. fans, and electric water pump in the future to assist in removing heat soak between runs. I'd like to be able to run an oil cooler with fan, aux coolant fan and radiator fan, and coolant pump between runs without running the car. I think that would be pretty slick.
 

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I hate to bring a thread back from the dead, but I have a quick question.

While renting an OBD-II tool from the Zone, I decided to watch the reading from the temp sensor. My gauge would sit between N-O and according to the Tool, the temp was right around *185-*189. I noticed while driving it around that the temp gauge would not budge, yet the reading from the tool would go as high as *194.

Once parked, the temp would drop back down into the high 180's. Fan never cut in, but the temp never seemed to get high enough to require it. And the gauge never moved.

Should I at all be concerned with A) my gauge being stubborn, or B) My actual readings being inconsistent?

I have an aftermarket digital gauge I use in my 3 series and the temp is ALWAYS a steady 239*. Even on track day or heavy traffic. I know a BMW is a bit more advanced than our birds, but I just want to be sure my car is well within spec. I have no qualms with swapping T-stats on this car, and the radiator is fairly easy. So are all the hoses. So I'm not afraid of changing parts.

-Zach
 
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