Engine temperature reading

[Luma46]

After reading some posts on the thermostat issues, I wonder if I should be worried about my engine temperature reading. It is showing about one third past/between the second and the middle mark on the temperature gauge. This is a 2007 V6, which I purchased recently, so I do not know what was it showing when new.
I have had vehicles that were always showing temperature right in the middle, and others (like my 1996 Pathfinder that I sold last year) that would show temperature around one quarter of the full scale right from being brand new and even after thermostat replace.
It has been my experience as well that those engine temperature gauges/sensors are very sensitive, 2 or 3 deg.C can easily show as a quarter of the scale difference.
Could anyone recommend the best spot to check the actual temperature on the engine with an infrared thermometer?

[fdryer]

How about pointing it at one of the radiator hoses coming from the engine? One will be from the thermostat so it would be the hottest or else just keep taking a reading from various spots to see the highest temperature reading. If you know where your coolant sensor is located, point your infrared sensor there. :cool:

[far2grumpy]

After reading some posts on the thermostat issues, I wonder if I should be worried about my engine temperature reading. It is showing about one third past/between the second and the middle mark on the temperature gauge. This is a 2007 V6, which I purchased recently, so I do not know what was it showing when new.
I have had vehicles that were always showing temperature right in the middle, and others (like my 1996 Pathfinder that I sold last year) that would show temperature around one quarter of the full scale right from being brand new and even after thermostat replace.
It has been my experience as well that those engine temperature gauges/sensors are very sensitive, 2 or 3 deg.C can easily show as a quarter of the scale difference.
Could anyone recommend the best spot to check the actual temperature on the engine with an infrared thermometer?

I have 05 Vue 3.5L and the temperature gauge generally stays mid-way between second and middle mark during vehicle operation. I also have a ScanGaugeII installed and the actual water temp - with gauge in indicated region - varies between 195 and 205 degrees F. The lower number applies at highway cruise and higher number prevails at low speed, stopped and idling.

Our typical daytime temperatures are in the low 70's this time of year and the cooling fans have not yet ran (except automatically when AC on).

I expect water temperature to increase as weather warms during in-town driving.

Incidentally, the cooling fans operate at predetermined water temps ... use following for an idea of engine temp (apply to 3.5L engine only):

The PCM (powertrain control module) commands the fan ON under the following conditions:

Low fan ON when coolant temp exceeds approximately 98°C (208°F).

High fan ON when coolant temp exceeds approximately 102°C (216°F)

High fan runs for 300 seconds at key off if temp exceeds 112 C (234 F). Will reduce to low fan at 102 C (216 F) if time remains.

A/C refrigerant pressure exceeds 361 kPa (52 psi) Low Fan Speed.

A/C refrigerant pressure exceeds 2100 kPa (300 psi) High Fan Speed.

[far2grumpy]

Luma46 ... in case you're not acquainted with operation of the Vue's cooling fans.

I do believe 04 / 07 3.5L Vues have similar cooling systems ... in this case two fans (left and right).

When the BCM outputs a LOW fan request (98C / 208F) one relay is used to operate both left and right fans in series - this provides approximately 6 volts to each fan motor - resulting in half-speed.

When BCM outputs a HIGH fan request at (102C / 216F) the LOW fan relay remains activated, plus two others latch to provide full 12 volts to both fans (they do roar at this point).

There's a schematic for fan operation at following thread (post #2) if interested.

http://www.saturnfans.com/forums/showthread.php?t=135235

[far2grumpy]

Luma46 ... please mentally change BCM references in above post to PCM. :blockhead

[Luma46]

Luma46 ... in case you're not acquainted with operation of the Vue's cooling fans.

I do believe 04 / 07 3.5L Vues have similar cooling systems ... in this case two fans (left and right).

When the BCM outputs a LOW fan request (98C / 208F) one relay is used to operate both left and right fans in series - this provides approximately 6 volts to each fan motor - resulting in half-speed.

When BCM outputs a HIGH fan request at (102C / 216F) the LOW fan relay remains activated, plus two others latch to provide full 12 volts to both fans (they do roar at this point).

There's a schematic for fan operation at following thread (post #2) if interested.


Thanks a lot 'far2grumpy', you are always very helpful and very factual. Actually I do realize that I have at home the scan interface that connects to my HP Pocket PC that I have not used at least 2 years. I have to try if it tells me anything ...

[tjr002]

I agree

[1saxman]

The gauge indication posted is the correct indication, one-third to halfway between the 1/4 and 1/2 marks. The thermostat will fail safe, or cold, which will throw a P0128 code and the SES light. When the gauge goes down almost to the 1/4 mark and pretty much stays there, you'll need a thermostat. The gauge can go almost all the way up to the end (where the red is) under extreme conditions, which is why you must keep the coolant level in the surge tank no higher cold than the cold fill line, to give plenty of room for expansion. Now, I've never seen the gauge go over the halfway mark in either one of ours even under the worst conditions. Generally you are using the AC in my area in hot weather when overheating is more likely, which automatically runs the auxilliary cooling fan. Even when the AC is not on, the aux fan will come on when the gauge gets close to the halfway mark, and you can see the temp rapidly coming down. You should also check from time-to-time to see that the coolant level in the surge tank rises on a hot engine (as soon as you get home on a hot day) and lowers on a cold one (before starting it the next day). This means the system is airtight and full of coolant, with minimal air space. While you're looking, the DexCool should be transparent orange/red. If cloudy or discolored, you need coolant service ASAP.

[far2grumpy]

The gauge indication posted is the correct indication, one-third to halfway between the 1/4 and 1/2 marks. The thermostat will fail safe, or cold, which will throw a P code and the SES light. When the gauge goes down almost to the 1/4 mark and pretty much stays there, you'll need a thermostat. The gauge can go almost all the way up to the end (where the red is) under extreme conditions, which is why you must keep the coolant level in the surge tank no higher cold than the cold fill line, to give plenty of room for expansion.

I posted earlier about seeing 195 to 205 degrees F on the ScanGaugeII in my 05 Vue V-6 doing mostly city driving. I recently completed a 2000 mile circuitous journey from my home city down to the hills of Arkansas, north to Omaha and returned to home plate.

I had the cruise on 75 for all interstate driving and the water temp stayed solid at 183 degrees on the interstate. The outside air temp reached into the mid 90's more than once and the intake air temperature reached 140 degrees when traveling on sun-baked asphalt and 90+ degree temperatures.

I used 10% ethanol when available because of the 10 price difference, but my average for 2000 miles (highway and city) was 23.5 mpg.

The back and rump grew weary but you gotta love the Vue ... didn't miss a lick, didn't use a drop of oil, and IMO has far more power than a vehicle that size and weight requires. (I also need to say it was just me and my fishing tackle - and cooler filled with various beverages).