FAQ: Engine Coolant Temperature & Fan Turn-On

Nate that is going to happen because the fan settings have not been lowered to match the thermostat. The fans are run by the PCM and are still programmed to turn on at 210 or whatever that setting is. Nothing to worry about.

What temperature should I be reading with a 190 Thermostat and engine idling for 20 minutes in 70 degree weather? The car is a 98 with 40,000 miles, and original thermo, but fresh anti-freeze. At what temps do the two fans come on? Each fan come on at a different temperature? With Air Cond on or off?
Should the gauge read a little above 200?

The OEM thermostat is a 195º unit. Driving, the temp will run between 190-200ºF. Idling, it will easily go above 200º. On hot days it will hit 210º F at idle, as the fans aren't set to come on until above that point. I believe the fans run at two speeds. Some say AC on commands the fans to turn on, but I have not noticed it.

205º is warm, but not overheating. 220º isn't good, but safe for normal driving. 230ºF is when I'd start getting concerned.

AA wrote:

The OEM thermostat is a 195º unit. Driving, the temp will run between 190-200ºF. Idling, it will easily go above 200º. On hot days it will hit 210º F at idle, as the fans aren't set to come on until above that point. I believe the fans run at two speeds. Some say AC on commands the fans to turn on, but I have not noticed it.

205º is warm, but not overheating. 220º isn't good, but safe for normal driving. 230ºF is when I'd start getting concerned.

I believe only one of the fans comes on to cool the Condenser. You can't hear it with the windows up and the radio on, which is the usual practice with the A/C on

Thanks guys, just wanna make sure all is functioning as designed.

Just a quick question, how fast does the 1995 Riviera warm up? Mine seems to warm up almost instantly. Temperatures have been around the freezing mark the last few days, and the car seem to come up to operating temperature in about 1-2 miles. It stays rock solid at a good temp, and I haven't seen it go over about 190 yet, but all the same I'm worried (silly I know) it warms up wwwaaayyy faster than anything I've ever driven.

Mine takes about 7-8 minutes idling in the drivevway at about 30 degrees farenheit. Takes 4-5 minutes of driving it.

If you're getting hot air out of the vents when it's showing it's warm, no reason to worry about a potential issue.

check for coolant in the oil and oil or exhaust fumes in the coolant... if you don't find fluid or gas where it does not belong, don't worry about it -- but then decide whether to connect the car to a scanner (NOT A CODE READER) to watch the coolant temp sensors. It may be that you have a worn temp sensor that, although it works, is no longer linear with temperature change in its operating range. Next thing to check (as has been posted elsewhere) is the cavity between the radiator and AC condenser; it's inconvenient but not difficult to check, requires removing the shroud over the radiator. The cavity accumulates debris over time and the debris cuts airflow. I notice you're located in Canada (in Chatham specifically). Except for a long pull up a long hill somewhere in midsummer I doubt that operating conditions where you are would tax a partially-blocked radiator. I bet, however, that one thing the previous owner noticed was that under that condition (long hill long pull in summer) the car heated up fairly high. (the other thing informing my guess is that you did not post any comment about your observations of the car's operating temp during the past summer)

The '95 - '99 Riv warms up reasonably quickly although yours sounds particularly quick to warm. In order for the car to operate properly (the HVAC for instance) and economically (the PCM's choice of fuel trim for instance) it needs to be warmed up. Since it sounds like you have a little time on your hands and you are interested, the things you can do quickly would be:

* while car is stone cold open the radiator cap and look for oil in the coolant and smell for the aroma of exhaust. if you find oil floating there or it smells like exhaust fumes you may have a head gasket leak. Put the cap back on...

* if you have an hour to 2 hours, remove the fiberglass shroud over the radiator and remove the debris that invariably accumulates there... put it back together, then start it up, and see if it warms up as fast as before (probably not)...

* while running just after startup pull the oil dipstick. You are not looking at the level, you are looking at the stick... is there any coolant on it? It would look like beads of water on the oily stick... Or is it really condensation? Whatever it is, note the condition, wipe it clean, check again, wipe clean, done for now.

* while running open the oil cap and see if the opening exhibits vacuum or pressure. Tell us.

* check that dipstick again, note the condition

* when car is warmed up, look in the overflow bottle. Any gas bubbles coming in from the radiator? If so, you've a head gasket leak.

* check dipstick (this is last time), note the condition.

let us know what you find Trevor.

Albertj

Put a scan tool on it and monitor coolant temperature. See if it agrees with the gauge.

Sounds like you might have an air bubble in the system but it's not bad enough to cause a temp spike.

Noticed during a 200 mile trip yesterday that my temperature gauge seems to be reading low. The entire trip from home and even at speeds of 80MPH I was reading add the mark just past 100 (The first thick line)

After reaching the destination and going through several stop-start routines it reached the normal level. Cycled it again at a gas station and it was reading low again. Anything to be concerned about? Temp was about 40F outside.

Ah....over-cooling. Either your thermostat is fuct (stuck open), or your Coolant Temp Sensor could be messin up. Also, make sure the coolant level is ok.

I'd have someone put a scan tool on it. Could just be the gauge or sender. I believe the coolant gauge and the computer get their readings from 2 different places. A scan tool will tell you what the coolant temperature sensor is telling the computer. I think if it was really running that cool, it would light a check engine light.

Are you getting adequate heat out of the vents?

manofmany wrote:

Noticed during a 200 mile trip yesterday that my temperature gauge seems to be reading low. The entire trip from home and even at speeds of 80MPH I was reading add the mark just past 100 (The first thick line)

After reaching the destination and going through several stop-start routines it reached the normal level. Cycled it again at a gas station and it was reading low again. Anything to be concerned about? Temp was about 40F outside.

The OE thermostats are designed to fail open. (I had one do that on my Riv...)

Time to scan but odds are your thermostat is wack.

Albertj

albertj wrote:

manofmany wrote:

Noticed during a 200 mile trip yesterday that my temperature gauge seems to be reading low. The entire trip from home and even at speeds of 80MPH I was reading add the mark just past 100 (The first thick line)

After reaching the destination and going through several stop-start routines it reached the normal level. Cycled it again at a gas station and it was reading low again. Anything to be concerned about? Temp was about 40F outside.

The thermostats are designed to fail open.

Time to scan but odds are your thermostat is wack.

Albertj

I guess youre right..but if you dont buy a special"stuck open" thermo,a standard Stant fails in the closed position..

robotennis61 wrote:

albertj wrote:

manofmany wrote:

Noticed during a 200 mile trip yesterday that my temperature gauge seems to be reading low. The entire trip from home and even at speeds of 80MPH I was reading add the mark just past 100 (The first thick line)

After reaching the destination and going through several stop-start routines it reached the normal level. Cycled it again at a gas station and it was reading low again. Anything to be concerned about? Temp was about 40F outside.

The thermostats are designed to fail open.

Time to scan but odds are your thermostat is wack.

Albertj

I guess youre right..but if you dont buy a special"stuck open" thermo,a standard Stant fails in the closed position..

I fixed the post

I'd have to see if you popped that thermo in backwards... (heeeeee).

Albertj

LARRY70GS wrote:

I'd have someone put a scan tool on it. Could just be the gauge or sender. I believe the coolant gauge and the computer get their readings from 2 different places...

That's a negative. There is just the one temperature sensor that feeds the PCM, then the PCM sends serial data to the IPC 'brain', which decodes it and actuates the gauge motor.

Abaddon wrote:

Also, make sure the coolant level is ok.

L67 wrote:

Are you getting adequate heat out of the vents?

x2

For anyone who is curious about the thermostat thing, a mini-lecture:



There are two kinds of thermostats. The short ones usually stick closed. The longer, bigger ones are called fail-safe thermostats by some in the trade, and when they die they stick open so the engine does not overheat. You might be able to see both types for one application if you ask a counterperson at a full-line parts store like a NAPA -- and if it's not busy at the moment.

Thermostats, also, can open too late, too slow, or not adequately -- basically a fail-safe thermostat has a little coil spring (to push it closed) and a ball of wax (holding it closed). The hot coolant melts the wax and when melted it allows the thermostat to push open against the spring. . When the car is shut off the spring pushes the thermostat closed. As the car cools off the wax hardens and holds the thermostat closed until the next drive cycle.

So what happens when it quits working right?

If the spring gets weak and wax is gone it might sit open and car will run too cool. If the ball of wax (it's sealed in the metal gadget in the spring) gets messed up for some reason, wax leaks out, the thermostat won't sit open but car may warm up funny, sometimes, depending on how hard you are revving it. I've never seen one with a broken spring. I've seen cheap ones with fatigued springs (compare the removed one to a new one). IF you replace it yourself AND you get a good one it's entirely possible you won't have to replace it again. Word to the wise: consider getting the OE thermostat 24505924, it comes with gasket/o-ring. Your problem is it's usually priced 3x the cheapies - a Gates standard thermo for this application runs like $3.50 on rockauto.com and the OE is about $10. Go figure. Maybe one of the pro mechanics on the site will comment further.

Albertj

Eldo wrote:

LARRY70GS wrote:

I'd have someone put a scan tool on it. Could just be the gauge or sender. I believe the coolant gauge and the computer get their readings from 2 different places...

That's a negative. There is just the one temperature sensor that feeds the PCM, then the PCM sends serial data to the IPC 'brain', which decodes it and actuates the gauge motor.

OK, in that case, a quick scan will tell whether the sensor and the gauge agree, and if not, it's a gauge problem.

Sorry guys, spent almost 20 hours removing snow yesterday.

Anyways. coolant level is fine. I do get adequate heat from the vents, even with the sub-zero temperatures we had today. My thought was that the thermostat was sticking open also. Not sure what brand is in there as it's been in there atleast 2.5 years.

Is the OE thermostat rated at 180 degrees or 195? I'm thinking mine has always been right around 180.

EDIT: Come to think of it, I think I may have replaced it with a 180 degree thermostat 2.5 years ago. I didn't remember replacing it at first, but now I remember doing so because the thermostat housing was warped.

manofmany wrote:

Is the OE thermostat rated at 180 degrees or 195? I'm thinking mine has always been right around 180.

EDIT: Come to think of it, I think I may have replaced it with a 180 degree thermostat 2.5 years ago. I didn't remember replacing it at first, but now I remember doing so because the thermostat housing was warped.

The OE is 195.

Might want to get a good stat and replacement housing from RockAuto (they have both)?

Albertj

I'm running at about 205 before the thermostat pops, and that is in Chicago winter with the heat blasting. I really need to change that to a 180 degree thermostat. Just bought the car and not at all comfortable with that needle being over 200 (if the gauge is accurate that is).