Coolant temp increase ?

[Hall]

What would cause my '08 G35 (169k miles) to occasionally have the coolant temperature increase ? By increase, instead of the needle being around the 8 o'clock position, it moves to 9 or even 10 o'clock. It has ONLY done this when it's 90º F or higher, AC is on, and I'm not moving. So far - knock on wood - I've been able to turn off the AC and crank the heat and that controls it. This isn't a frequent occurrence either. In 3-4 years, it's maybe happened 7-8 times. Coolant overflow tank level is okay but it does need topped off maybe every 18 months. No signs of leaks otherwise.

When I've been able to check, both cooling fans are working. It happened today, I turned on the heat, etc and was home in less than 10 minutes. I left it idling in my driveway, AC off, and both fans were working. I am a little familiar with Hondas which tend to have 1-2 coolant temp sensors - do these have them ? No check-engine codes are triggered. How do I diagnose what it is ? If it were the thermostat, I'd think it would happen more frequently and at other times or situations but in my case, it's very consistent conditions for IF it will happen. I'm not interested in replacing random parts and crossing my fingers either.

 

[Number_35]

My first thought was that the cooling fan (the one that draws air through the radiator) was not working, but reading on it looks like you've determined that it is.

How is the coolant level?

 

[SHOZ]

Just how much in degrees does it change? My temp gauge on the Gen Coupe is a glorified idiot light. If I did see it move once warmed up it's probably too late and already overheated.

 

[Hall]

My first thought was that the cooling fan (the one that draws air through the radiator) was not working, but reading on it looks like you've determined that it is.

I haven't checked while the temperature was up, only afterwards and as soon as I was able to. My main concern when that happened was to get it cooled down. Mine has (2) fans - one always runs, I think, and the 2nd only runs when really needed or if the AC is on. If I check right now, with the AC on, and the temperature gauge in the normal position, both fans spinning.

How is the coolant level?

Coincidentally, I just had a couple heater hoses replaced. On VQ engines, Nissan likes to put a bleed valve in line on one side and a useless, plastic coupling on the other. Both are notorious for cracking and failing with age. I replaced the coupling 1-2 years ago and just in the past 2 weeks, I had a shop replace the other (dropped car off while we were on vacation) along with draining and refilling the coolant. They charged me for 2 gallons.... The VQ engines can sometimes be a pain to bleed the air out of them, which I didn't do when I replaced the coupling. I never had any symptoms of air in the system though. These temperature rise had happened a couple times BEFORE I replaced it too, for what that's worth. The overflow tank level has always stayed between the MIN and MAX lines although I have had to top it off twice in 5-6 years. I would like to think that's not unusual.

 

[atikovi]

16 year old 169k car? I'd say the radiator is loosing it's efficiency from restricted passages inside or dirt and leaves on the outside blocking air flow.

 

[Hall]

Just how much in degrees does it change?

Mine has a "dial" (well, a half-dial). You could say it goes from 7 o'clock to 11 o'clock. I know where the normal position is and if it moves even the slightest amount up, I notice. Drove home today, in 95º F, AC on full-blast, with speeds from 0-5 mph in line at a stop sign up to 65 mph, and it was fine.

I do have an OBDII adapter but I need an Android device for it. The one I have that is supposed to work with an iPhone doesn't connect.

 

[Hall]

16 year old 169k car? I'd say the radiator is loosing it's efficiency from restricted passages inside or dirt and leaves on the outside blocking air flow.

Nothing on the outside restricting anything. If it were a thermostat or radiator, I'd think it would act up more often. It only happens in the scenario I mentioned and even then, not every time. Luckily, it's not a frequent occurrence.

 

[97prizm]

What would cause my '08 G35 (169k miles) to occasionally have the coolant temperature increase ? By increase, instead of the needle being around the 8 o'clock position, it moves to 9 or even 10 o'clock. It has ONLY done this when it's 90º F or higher, AC is on, and I'm not moving. So far - knock on wood - I've been able to turn off the AC and crank the heat and that controls it. This isn't a frequent occurrence either. In 3-4 years, it's maybe happened 7-8 times. Coolant overflow tank level is okay but it does need topped off maybe every 18 months. No signs of leaks otherwise.

When I've been able to check, both cooling fans are working. It happened today, I turned on the heat, etc and was home in less than 10 minutes. I left it idling in my driveway, AC off, and both fans were working. I am a little familiar with Hondas which tend to have 1-2 coolant temp sensors - do these have them ? No check-engine codes are triggered. How do I diagnose what it is ? If it were the thermostat, I'd think it would happen more frequently and at other times or situations but in my case, it's very consistent conditions for IF it will happen. I'm not interested in replacing random parts and crossing my fingers either.

Coolant level or the thermostat is getting lazy. I had this happen on my neon, then one night on my way to work the temp just kept rising and I had to pull over.

 

[SC Maintenance]

Until you monitor it in real time on OBD, you really don't know what the temp is. It could be going up a small amount, or a lot?

 

[oldcodger]

I vote for a slowly failing thermostat.

 

[eljefino]

Stand next to it when it's really hot, near the a-pillar by the driver's door is fine. You should feel the fans THROWING heat. If they aren't, it's an air flow problem (bad fan motor or control) or water flow problem (water pump or clogged radiator).

That doesn't narrow it down much. But a well functioning system should throw lots of heat at you. If you have another car to compare to, do so.

Since your heater core sheds enough heat to bring things within reason, I think the water pump is fine and your radiator is compromised.

 

[nicholas]

What would cause my '08 G35 (169k miles) to occasionally have the coolant temperature increase ? By increase, instead of the needle being around the 8 o'clock position, it moves to 9 or even 10 o'clock. It has ONLY done this when it's 90º F or higher, AC is on, and I'm not moving. So far - knock on wood - I've been able to turn off the AC and crank the heat and that controls it. This isn't a frequent occurrence either. In 3-4 years, it's maybe happened 7-8 times. Coolant overflow tank level is okay but it does need topped off maybe every 18 months. No signs of leaks otherwise.

When I've been able to check, both cooling fans are working. It happened today, I turned on the heat, etc and was home in less than 10 minutes. I left it idling in my driveway, AC off, and both fans were working. I am a little familiar with Hondas which tend to have 1-2 coolant temp sensors - do these have them ? No check-engine codes are triggered. How do I diagnose what it is ? If it were the thermostat, I'd think it would happen more frequently and at other times or situations but in my case, it's very consistent conditions for IF it will happen. I'm not interested in replacing random parts and crossing my fingers either.

Get a simple scanner.....
Elm 27 is a great one....
The free Car Scanner, blue pic provides a ton of info.

For our old Honda , Rislone hyper cool reduced coolant temps 10c across all usage, especially during the hottest week ever in Orlando.

It's good stuff that actually works.

 

[nicholas]

Could also be an air bubble , pocket in the system.
Burping it is easy........

 

[Marcozi]

Mine has a "dial" (well, a half-dial). You could say it goes from 7 o'clock to 11 o'clock. I know where the normal position is and if it moves even the slightest amount up, I notice. Drove home today, in 95º F, AC on full-blast, with speeds from 0-5 mph in line at a stop sign up to 65 mph, and it was fine.

I do have an OBDII adapter but I need an Android device for it. The one I have that is supposed to work with an iPhone doesn't connect.

What app and communications adapter are you using? I run obdfusion on my iPhone without problem. So apps are finicky about the adapter.

 

[Hall]

Could also be an air bubble , pocket in the system.
Burping it is easy........

This is what I'm gonna try first. Already ordered a no-spill coolant funnel. Are you familiar with VQ engines ? With a no-spill funnel and maybe jacking up the front end a little, I don't see the point of the inline bleeder Nissan puts in the heater hose line since it will be 6-12" lower than the funnel.

 

[oil pan 4]

What would cause my '08 G35 (169k miles) to occasionally have the coolant temperature increase ? By increase, instead of the needle being around the 8 o'clock position, it moves to 9 or even 10 o'clock. It has ONLY done this when it's 90º F or higher, AC is on, and I'm not moving. So far - knock on wood - I've been able to turn off the AC and crank the heat and that controls it. This isn't a frequent occurrence either. In 3-4 years, it's maybe happened 7-8 times. Coolant overflow tank level is okay but it does need topped off maybe every 18 months. No signs of leaks otherwise.

When I've been able to check, both cooling fans are working. It happened today, I turned on the heat, etc and was home in less than 10 minutes. I left it idling in my driveway, AC off, and both fans were working. I am a little familiar with Hondas which tend to have 1-2 coolant temp sensors - do these have them ? No check-engine codes are triggered. How do I diagnose what it is ? If it were the thermostat, I'd think it would happen more frequently and at other times or situations but in my case, it's very consistent conditions for IF it will happen. I'm not interested in replacing random parts and crossing my fingers either.

Test your anti freeze and water percentage.

 

[Hall]

What app and communications adapter are you using? I run obdfusion on my iPhone without problem. So apps are finicky about the adapter.

I thought in years past, Apple didn't allow adapters to talk via Bluetooth. I have an ELM327 adapter that I've had for years but always used it with an Android. I did buy an adapter from CARISTA that works with iPhones but I've never gotten it to connect to my iPhone using Torque+. It's supposed to be able to work with it.

I forgot about the INNOVA plug-in reader (6100P) I have. I can try it as well. Thing is (knock on wood), this temperature rise isn't common. I could start the car in my driveway, crank the AC, and let it sit and it might happen...

 

[Hall]

Connected my scanner just a bit ago. Mind you, everything was operating okay. Outside temperature is around 96º F. The gauge was in the "normal" position but interestingly, it did NOT move, that I could notice, with the variance below. I recall a post from @Astro14 a while ago indicating that the gauges in modern cars are, to some degree, calibrated with a lot of slop. That is, the needle position is controlled so that it doesn't fluctuate up and down constantly even when coolant temperatures can go up and down.

Idle, AC off
205-214ºF

Driving, AC on
198-199º F

 

[Craig in Canada]

What would cause my '08 G35 (169k miles) to occasionally have the coolant temperature increase ? By increase, instead of the needle being around the 8 o'clock position, it moves to 9 or even 10 o'clock. It has ONLY done this when it's 90º F or higher, AC is on, and I'm not moving. So far - knock on wood - I've been able to turn off the AC and crank the heat and that controls it. This isn't a frequent occurrence either. In 3-4 years, it's maybe happened 7-8 times. Coolant overflow tank level is okay but it does need topped off maybe every 18 months. No signs of leaks otherwise.

When I've been able to check, both cooling fans are working. It happened today, I turned on the heat, etc and was home in less than 10 minutes. I left it idling in my driveway, AC off, and both fans were working. I am a little familiar with Hondas which tend to have 1-2 coolant temp sensors - do these have them ? No check-engine codes are triggered. How do I diagnose what it is ? If it were the thermostat, I'd think it would happen more frequently and at other times or situations but in my case, it's very consistent conditions for IF it will happen. I'm not interested in replacing random parts and crossing my fingers either.

Curious - do you have a reason to feel this is actually a problem? The real temperature of the coolant can be all over the place, and you've reported that when it's really hot out, it reads hotter. That's....expected. Unless of course you've owned the car for 10 years and the temperature has never moved before and suddenly now it is.

Most gauges are heavily buffered, meaning they're little more than temperature idiot lights. A huge range of temperatures shows exactly the same place on the gauge because that's what the software/electronics are designed to show you. They've done this so that folks don't freak out when it moves, but it also hides what's really going on from those who would like to see instrumentation show reality. When I've had a car with a true temperature gauge, the temperature often changed depending on weather and driving conditions.

You could be chasing a whole lot of troubleshooting for nothing if you don't actually have a problem.

 

[someonesomewhere]

Curious - do you have a reason to feel this is actually a problem? The real temperature of the coolant can be all over the place, and you've reported that when it's really hot out, it reads hotter. That's....expected. Unless of course you've owned the car for 10 years and the temperature has never moved before and suddenly now it is.

Most gauges are heavily buffered, meaning they're little more than temperature idiot lights. A huge range of temperatures shows exactly the same place on the gauge because that's what the software/electronics are designed to show you. They've done this so that folks don't freak out when it moves, but it also hides what's really going on from those who would like to see instrumentation show reality. When I've had a car with a true temperature gauge, the temperature often changed depending on weather and driving conditions.

You could be chasing a whole lot of troubleshooting for nothing if you don't actually have a problem.

Mirrors my thoughts on his "issue". Above 90, AC on, car sitting still? Of course it's going to get hotter. As long as it isn't overheating, it's expected, normal, and completely fine.