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"Normal" Cooling System? Or a problem?

2000 Oldsmobile Silhouette, 128K.



I bought the van with 104K about 18 mos ago. My wife normally drives it so unfortunately I can’t say everything about the history or consistency of things regarding my question.



Every vehicle I can recall owning (including the other 2 I have now) had a cooling system that held the car’s temperature rock solid with no noticeable variation - unless something was wrong. This one, not so much.



The short story is that the thermostat is 195 deg (OEM temp), but the fans do not kick on until about 230-240. I don’t think that’s right, but maybe some cooling systems just work that way. (My Haynes manual is silent on all by the 195 degr thermostat).



The longer story:

- The gauge is not numbered. I recently spent some time with IR thermometer trying to get actual temps.



- Judging by watching gauge readings next to my IR thermometer readings - while driving down the road the temp needle holds steady at the gauge point that corresponds to the 200 degree range.



- If you stop and idle long enough the temp gauge climbs about a quarter/third (from say .33 to .66 up the gauge) until the fans kick on - the temp range there is 230-240 (I’d be more precise but its cramped under there and hard to get a reading I fully trust next to the temp sensor). It never gets near the red.



- The fans then bring the temp back down to the 200 range, and it will do this cycle again if you let it idle long enough.



- So, in one respect all of that seems “normal.” In another respect it doesn’t sit well with me.



So what say you?



Other details (for those who want them): the car spent its life on DexCool. I had that flushed out pretty much immediately and since then have drained & refilled once. It now runs a universal coolant (yellow).



I replaced the thermostat about 12mos ago after a P0125 code and test of the other system components. I replaced it with OEM 195 degr and it is functioning. No codes, and it opens and closes.



As near as I can tell the cooling fans are PCM controlled with info from the temp sensor. The temp sensor has been tested for actual resistance variation, and the gauge movements next to IR thermometer readings reinforce the notion that the sensor is doing its job.

The t-stat is functioning normally for this engine.

I had the same van and the same operating temps.

I too wondered about the climb in temp while idling and asked GM (via their website) and they told me the reason for the higher temp when stopped (in gear) or idling (in neutral) is to burn off the higher emissions when doing this, rather than the temp remaining in the normal range while travelling.

Thanks Roadrunner - I was actually thinking that if I could just drive another one of the same year to see what it does I would learn something. Your experience is the next best thing.

I’m not thrilled about the extra heat in the transmission - I’d rather it stay as cool as possible.

Roadrunner covered your question. I just want to comment on your other cars. It is likely that the reason that the temperature appeared so stable is that some cars (I know my Volvo and BMWs are this way) have a compensation circuit on the back of the temperature gauge. It holds the needle steady in the middle of the span over a fairly wide range of temperatures. The needle does not move up unless the car is so hot that a problem is indicated.

Thanks. I had never heard of such a thing. It maked me so curious that I am going to play around now with the other two cars and the IR thermometer. (What’s the point of a toy if you don’t play with it?)

Manolito is correct.
The temperature gauge on many modern cars is “buffered”, and will essentially have only three readings:
Stone Cold
"Normal"
Overheated

Since it takes a few seconds for the gauge to move from “stone cold” to “normal” when the engine actually reaches normal operating temperature, it appears that the gauge is accurately measuring the increased temperature in precise gradients, but it is really not doing that.

Similarly, when the engine’s temp rises to a dangerously high level, it will take a few seconds for the gauge to rise to the very hot level, even though the engine’s temp has been steadily rising for…maybe several minutes.

Essentially, many/most of the temperature gauges nowadays are really glorified idiot lights, and don’t give an accurate indication of rapidly rising engine temps as gauges did on older cars. You might say that these modern gauges give a false sense of security since they really only have three indications on most cars: Cold, “normal”–which actually encompasses a somewhat wide range into one specific reading, and “overheated”.

Others have answered your question. This seems normal for your vehicle. As long as the cooling fans kick in all is fine.

The thermostat is not a regulator of engine temp, is simply stays closed to allow the coolant to stay in the block until it opens up when the coolant reaches the set point, 195 in this case. After that the thermostat stays open regardless of how high the engine temp goes. Therefore the thermostat sets the minimum temp for a warmed up motor.

The maximum temp allowed is whatever the sensor is set for to kick on the cooling fans. From your measurements that is about 235 degrees. If you want to reduce that max. temp you have to locate the proper sensor and see if there is one available that kicks in at say 220 degrees. If there is and you install it you could find your electric cooling fans run much more frequently and for longer periods which could burn the fans out quicker.

Since the guage isn’t approaching the H or red zone, I’d leave it alone.

Thanks for the tutorial, Uncle T. I had been wondering about that ever since I wound up with a wandering Temp guage indication after I changed the thermostat on '94 Taurus (the saga is documented on this Group).

What about older cars that did not have temp-controlled electric fans? Did they just try to pick a useful value air flow from the belt-driven fan?

The belt driven fan has two types. One is just a solid fan and the blade spins all the time. The other uses a “clutch” so the fan just spins (and therefore draws a bit of engine power) at slower engine speeds.

Either way once you are moving it is the airflow by the radiator from the cars motion that provides the cooling. Once you are going about 20 mph there is enough airflow that the fan isn’t needed. If it is the solid type and keeps spinning about 20 mph it isn’t adding anything to the cooling airflow, it is just spinning.

When you are sitting still the belt driven fans were needed to keep the air going by the radiator so the car won’t overheat. Sometimes I would get stuck on NJ’s famous Garden State Parkway which is a massive traffic jam on most nice summer weekends. After about 20 mins. of sitting the temp guage would go up and you’d have to rev the motor up to cool down the temp., or raise the hood, or turn off the AC. The electric fans are better particularly in todays cars which virtually all have AC.

Well, I should have just done this experiment to start with. I fired up my 95 Caravan which is one of those whose temp needles stays steady. It behaves exactly the same way without any of the variation registering on the temp gauge. 200 degr reads the same as 240. So my Silo gauge is just more “honest.” A while back someone posted a thread about not having gauges (I think it was about an oil pressure gauge). I’m the opposite - I want more gauges and I want them to be accurate. So I guess now I like my Silo gauge better than any others (tho I want it to have actual numbers on it).

Those of you who are in the know obviously could have told me this before I tried. But I’m always wanting to see for myself anyway. I don’t learn something new every day, but I do try.

Thanks all.

Interesting thread-for me anyway…

Thank you all who participated !