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Discussion Starter #1 (Edited)
I recently installed a 350Z T-stat in my '13 4.0 to help keep it from getting 'heat soaked' & to help it generally run better during these HOT Texas summers. The swap did indeed help it run cooler & run better overall. It now drives the same way it drives when its a nice & brisk fall day, but with the ambient temp at 90* or more. However, from what I've read on other 350Z T-stat threads, it seems as though it might now be running too cool. To give a few comparisons I put together a bit of a chart with the different t-stats I've used & the temps I ran with each. All of these noted temps are with the outside temp being 90* or more.

Stock t-stat: Fairly consistent temps
Driving nice & easy (55mph or less)= 191*-193*
Constant highway (70+mph)= 195*-198*
After driving highway speeds then stopped in traffic for ~10 min or more= up to 208*
Once moving again at highway speeds= after a mile or so temp would drop & stay 195*-198*
Overall avg temp= 193*-198*

First 350Z t-stat I installed: Numbers all over the place
After initial warm-up driving= 185*
Slow down for traffic then resume speed= would drop to 183* then climb to 192*
Highway driving (70+mph)= fluctuate between 185*-192* or more
Stop for red light or traffic= would climb from 185* to 199*+ within ~10 min or less
Once moving again at highway speeds= after a couple miles would drop from 199*+ to 184* then begin to fluctuate again
Overall avg temp= no idea

Current 350Z t-stat: Runs too cool??
Easy driving after initial warm-up= 177*-183*
Constant highway (70+mph)= 183*-187*
Come to a stop for traffic etc. (after ~10 min or more)= 190*-194* then will settle out at 190*
Once moving again at highway speeds= drops from 194*/192* then will settle out around 187*-183* after a mile or so
Overall avg temp= 185*(ish)

Now, I understand that driving conditions are always changing & that I'm always putting the engine thru different degrees of loads which in turn causes the coolant temp to constantly change. And, I also don't want this thread to turn into a "low temp t-stats are dumb because..." or anything else along those lines. That's not the intent of this thread. Rather, I want to hear from people who have done the 350Z t-stat or even a NISMO t-stat swap & what coolant temps you're getting during different driving conditions & how you're getting your numbers, i.e. Scan-gauge, Torque app, etc. Even if you haven't done the t-stat swap but you know what your coolant temp numbers are, I'd like to hear from all of you as well. I look forward to seeing what type of readings others are getting & seeing just how different but the same our trucks really are.

Thanks for looking!:)
 

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For sake of discussion, the 350Z thermostat is simply a lower temp unit? Does it flow any more or less freely when open?

With that said, I run a Bluetooth scanner and torque daily on my 215K mile beater car so I can monitor coolant temps (trying to be nice to a worn out old reliable beater) and I have noticed as you have how much coolant temps swing dependent on engine load, ambient temps and terrain.
 

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These motors are not like the old small block chevy's that love to run 170-175 all the time. They are designed to run at just below the boiling point of pure water. 195-200 is where they are the most efficient. A spread of 10 degrees is not a big deal. Mine runs 193-196 all the time and it's not had a hiccup in 187,000 miles. I have changed the coolant once in that time.
 

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260k miles on my stock 4.0L and still on the stock thermostat. Only time i had a problem was when my radiator was packed with sand/mud from wheeling and then the temp would creep up to the top 3/4 line of the temp gauge. I did some heavy duty cleaning of the radiator and now it's back to normal. Never goes about the 1/2 way mark, even when towing the boat on a hot Florida summer day.
 

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Discussion Starter #5
My apologies to all for the late replies. I was sick recently & have been playing catch-up on everything I've been needing/wanting to do so I've been a tad bit on the busy side lately. Anyways, lets get back to business.

Shizzy- Yes. The 350Z t-stat is exactly the same as ours (I believe MY '03-'07 are anyways) except it opens at a lower temp, 170* vs our stock 180*. Swapping the stock t-stat for the 350Z t-stat is a performance mod a bunch of the early Fronty owners jumped on quite a few years ago. Several members even installed the NISMO t-stat which opens at 155*. Those guys (RDR & Brutal are the only two I can currently think of) did a LOT of performance mods, so the NISMO t-stats worked well & were justified for their rigs. Neither the 350Z nor the NISMO flow anymore "freely" seeing how they're installed in the same identical housing as our stock units. However, I think I remember one of them saying the spring rate on the NISMO t-stat is different therefore making it open & close much quicker than the other two t-stats.


Texas Scout- I completely agree with what you're saying. Nearly all motors of late, including ours, run at a much higher temp than motors of years gone by. As you said, it helps them run more efficiently. Since the motor & the combustion chamber are both at a higher temp, the fuel gets vaporized much quicker which helps it burn more completely which then reduces emissions & increases fuel mileage.
I expected when I swapped out the t-stats that it might take a bit of a bite out of my mileage, but I also expected that when I bought my 285/75/16 E-rated tires as well. However, with my truck now running at the cooler temps it doesn't feel 'bogged down' anymore. It doesn't feel like it's 'tired' & wants me to pull over & wait till cooler temps arrive; say late October for us here in Texas. LOL! And, it hasn't taken any sort of bite out of my mileage what-so-ever. IF IF it has taken any mileage away from me its slightly marginal at best. I took waaaay more of a noticeable hit on my fuel usage when I switched to the bigger tires than with my t-stat. But of course going from stock tires to large E-rated tires & getting worse mileage is kinda a "duuuh" thing to. LOL!



Sangster- WOW! 260K miles & still going strong!?? Congrats man! That's awesome! Yeah, whenever I wash my truck I always wash thru the condenser & radiator to get all the dirt, bugs, & whatever else out from between the cooling fins. I do the same on the transmission cooler as well. And, depending on how the weather has been, I'll spray & wipe down the entire engine about once every 4-6 weeks. One thing I can't stand is a filthy engine. A clean engine not only looks better but it also runs better because it can more easily dissipate the heat from it compared to one that has mud, dirt, grease & grime all over it. Now, I understand that if you go off-road a lot or live where the roads aren't very good your engine is going to get dirty. BUT, I've seen motors that were so packed with gunk that you couldn't see the different parts of the casting & it looked like the sides of the block were smooth! THAT sort of stuff I just dont understand how people let happen, but yet those same people wonder why their car is always breaking down. Derrrrr.:roll:


Thanks to all of you for the great responses to this thread! I had a couple agendas for starting this discussion. 1) mostly curiosity to see how other peoples trucks run during varying driving conditions & the temps at which they're running at compared to how my truck does under the same conditions. and 2) to maybe revive an old mod seeing how there seems to be a LOT of new members who have no prior experience with a Frontier compared to us 'old timer Frontier owners'. Plus maybe get some feedback from a few of those 'old timers' that did this mod way back when & see how its been for them since doing it.
Thanks again to all of you for replying!:smile:
 

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Texas Scout- I took waaaay more of a noticeable hit on my fuel usage when I switched to the bigger tires than with my t-stat. But of course going from stock tires to large E-rated tires & getting worse mileage is kinda a "duuuh" thing to. LOL!


:
If may not be as bad as you think IF you are using your odometer to calculate your mileage. Remember your speedo and thus your odo will be off (slow) with the larger tires. If you went from 265 65 17 to 285 75 17 your speedo will be over 13% off! That means you will have 13% fewer miles on your odo for any given tank of gas. That makes a huge difference.
 

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Discussion Starter #7 (Edited)
TX Scout,

My truck didn't come with instant mileage, DTE or anything else. Even if it did I would only use those things as a guide. Ive always used the odometer to calculate fuel usage. Guess Im just old school like that. Plus, growing up & driving cars that didn't have all that fancy stuff on them, the odometer was the only way to figure out your mileage anyways.

About 6 months after I bought my truck I installed a set of white face gauges. After I put it back together a couple of the gauges were off including the speedo. It wasn't much, but eventually my OCD caught up with me. So, when I finished my RTMR install I made sure that all the gauges read correctly. Theres a couple of streets close to where I live that have radar signs on them. I drove by them at different speeds to make sure my speedo was accurate. I also have the Torque app & used it to set the needles for the other gauges. I did this after I bought the larger tires as well to make sure everything was reading as it should.

I thought the speedo on these trucks was read by the RPMs of the transmission & also sensors on the axles so that if you put different sized tires/wheels from stock it would still read correctly?? I mean a base model S has 15" wheels, the SV has 16", & the SL comes with 18". I would think/hope that 'somebody' at Nissan would've thought about the different sized wheels between models & figured out a way to keep the readouts accurate. OR is there something Im missing??
 

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Yeah, this is a funny thing. I went up one size with mine. to 18" wheel, however I used the tire size comparitor to make sure that my "rolling circumference" was identical to stock. That way my speedo would be correct. The weird thing is, it's always been 1.25-1.5 mph slow. Then it hit me, the PRO 4X has a size larger tire on it. I took that size and use the compairtor again and sure enough, that size would have corrected my speedo perfectly.

The only answer I get is that the speedo is calibrated for the PRO 4X only and then used on all models.
 

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Discussion Starter #9
The only answer I get is that the speedo is calibrated for the PRO 4X only and then used on all models.
Really?? Huh. If that's true, I wonder why Nissan did it that way? Guess they've done several things, not only to our trucks but to other models, that seems rather odd. Heres an example.

Im looking to install an full sweep electric oil pressure gauge on my truck soon & was checking if any of the Z/G guys had installed one since their engines are very similar to ours. The search results came up with quite a few threads about the Z's & G's oil & coolant temps running really high. Im talking coolant temps running 200-220 & oil temps running from 200-260 during normal driving! One of the guys finally got an 'official' answer from Nissan saying those temps are 'normal', but if they're concerned about the high temps &/or plan on running the car on the track then they should get an oil cooler so as to not cause further damage to the motor. Nissan even gave them an actual Nissan part number for the cooler. Furthermore, Nissan said that they're aware of the concern over the high temps but they didn't install the oil cooler at the factory because the additional cost would put the car out of the reach of more people. Seriously!?? So, I guess they figured rather than fixing a design fault they'd just sell a car for less in hopes that more people would buy it & not notice the temps at which it operates. Then I suppose they'd make even more money off the oil coolers if/when those people found out. Plus, they'd make money off the extra maintenance associated with premature engine wear due to excessively high engine temps.

All I have to say about that is; Wow.

That's why I'm sooo glad this site has the type of people on it that don't condemn others for not knowing what a lot of us have come to think of as 'common knowledge' about our trucks. And when we find a solution to a problem Nissan doesn't seem to want to address, they spread the word on how to correct it for cheap & how to do it ourselves.
 

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If Nissan says those are standard temps, then they are standard temps. I'm not sure how an individual decides what temperature their car should run at. Comparing old carbureted cast iron engines to Computer controlled fuel injected aluminum engines is not always a correct thing to do. I have a 1998 Chevy cavalier that runs all day at 195 degrees and swings as high as 206 in hot weather which I have found Chevy says is normal. Miles? 218,000 and still going strong. So much for premature wear....
 

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just because oil/water temp is high at one point in the engine, does not mean it's high everywhere.

Something weird I have noticed as of late on my Frontier, when I turn the engine off after a long highway run. I hear bubbling sounds coming from the heater core area. I'm not losing coolant, but I think it's developed an air bubble in there. I have noticed that my heater does not work well until i'm running at highway speeds or if I'm accelerating fairly hard.

Is there a "burp vent" on the back of the manifold like the VQ35 engine?
 

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These motors are not like the old small block chevy's that love to run 170-175 all the time. They are designed to run at just below the boiling point of pure water. 195-200 is where they are the most efficient. A spread of 10 degrees is not a big deal. Mine runs 193-196 all the time and it's not had a hiccup in 187,000 miles. I have changed the coolant once in that time.
I'm curious where you have your info from that the motor needs to run hotter...

I thought the speedo on these trucks was read by the RPMs of the transmission & also sensors on the axles so that if you put different sized tires/wheels from stock it would still read correctly?? I mean a base model S has 15" wheels, the SV has 16", & the SL comes with 18". I would think/hope that 'somebody' at Nissan would've thought about the different sized wheels between models & figured out a way to keep the readouts accurate. OR is there something Im missing??
The truck speedo is driven off of the ABS/wheelspeed sensor at the wheel. The trans speed sensor is used by the ECM. HOWEVER the BDGT takes its speed sample from the trans speed sensor, so when you shift into Lo range BDGT will report you're driving much faster than you are actually going.

Is there a "burp vent" on the back of the manifold like the VQ35 engine?
to burp it you have to park with the nose in the air and then run teh engine above idle.

The ECM enters Open program once it heats up above 165deg F. As long as its over this temp the ECM adjusts for air temp, engine temp, O2 measurement & knock sensor readings.

So I wouldn't worry about a cooler temp tstat being a problem. Cooler air charge delivers more power and as long as the engine isnt boiling over and teh trans is under 210 its all good. The trans is much more sensitive to high temps. over 220 is not good, and over 240 is Bad. Ideal is to stay under 200deg. For every 20 over 200 your trans life is cut by 1/2. ATF burns up faster, acids develop faster (in the atf),
 

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Discussion Starter #13 (Edited)
If Nissan says those are standard temps, then they are standard temps. I'm not sure how an individual decides what temperature their car should run at. Comparing old carbureted cast iron engines to Computer controlled fuel injected aluminum engines is not always a correct thing to do. I have a 1998 Chevy cavalier that runs all day at 195 degrees and swings as high as 206 in hot weather which I have found Chevy says is normal. Miles? 218,000 and still going strong. So much for premature wear....
Let me ask you a couple of questions, shizzy. First off, when did I ever compare an old cast iron motor to a new all aluminum motor? Because I don't recall doing that. I know the differences between the two & also know not to compare them. So, I'm not quite sure if that was directed at me or maybe TX Scout. If Scout, then I think he was simply giving me a bit of history between old school & new school motors based off my initial post & me stating that I had installed a lower temp t-stat. In my opinion, no harm & no foul.

Secondly, I think you pretty much missed the point of my previous post. It wasn't necessarily about the Z's & G's, but about some of the odd things Nissan does. Then I gave an example of an odd thing Nissan had done with the Z's & G's, which you seemingly missed the point of that as well. It didn't have much of anything to do with coolant temps but more so with oil temps of the VQ35 engine in the Z & G platforms. I found numerous threads about owners who were experiencing higher than usual oil temps & were wondering if anyone else had been experiencing the same & what they had done to correct it. The issue had become such a widespread concern that Nissan finally posted a statement & called the temps they were experiencing "normal". Do you seriously think Nissan would call it anything else?? Then, around that same time Nissan comes out with an oil cooler kit made specifically for those models. Convenient timing? Maybe. Covering their asses?? IMO, more than likely yes. BTW, this whole example is a very paraphrased version of about 40+ pages of threads I read. Why else would Nissan come out with an oil cooler kit specifically for those two models & no others even tho they had been in production for a few years if there wasn't an issue with the oil cooling system??

Think about this; what did Nissan do when thousands upon thousands of Frontiers, Xterras, & Pathfinders were having cross contamination issues between their radiators & transmissions?? Did they offer a recall? Hell no. Instead, they extended our warranty to 80K miles. Pfffft! Big deal. That was around the mileage when most of the contamination issues were reported!! And you CANT tell me Nissan didn't know when most of the contamination issues were happening either. They knew damn well when it was occurring. I know it happened around that time on my '06 Frontier because it had just shy of 90K miles when I had to replace & flush everything because of the contamination. So, if Nissan didn't fess up to a situation they knew for a fact was a design fault across three different models & hundreds of thousands of vehicles, do you really think they would fess up & admit they have oil cooling issues with 2 different models that share the same engine?? As long as it wasn't an 'imminent safety concern' then, no. If they did admit a design fault in the oil cooling system of the Z & G, they'd have to offer & install their oil cooler kit on both vehicles for anyone who wanted it for free. You think they were about to flip the bill for that?? Again, not a chance. If they ever were to admit fault to any of the above it would open them up to all sorts of legal mitigation & more than likely bankrupt them in a matter of a few years. Point of all this is, Nissan did exactly what many were expecting them to do...deny, deny, deny. After they denied any wrong-doing, they offered some sort of reconcilement so they can say they took 'corrective action' against the problem incase anyone tried to come back on them about it. In a nutshell, its all about CYA.

Furthermore, your comparison of your '98 Cavalier coolant temps to '03 & newer Z's & G's oil temps is a moot point. 195*-206* coolant temps for any modern vehicle is perfectly acceptable. However, the Z's & G's oil temps were running at 220*+ & that was under light load in 30*-50* weather. Several owners also stated that when they were in slow moving traffic their oil temps climbed as high as 260*. One guy even stated that after he laid into the skinny pedal a bit, his oil temp had shot up close to 300*!! That is NOT something that anybody with a good working sense of engines would consider "normal" by any means. As engine oil temps reach 250*+, the long chain molecules it once formed begin to break down. This is also true if the oil has fuel, coolant, or any other contaminants in it. Even under normal driving conditions engine oils can shear or breakdown from a 30 weight oil to as low as a 20 or 15 weight oil. And that's without any impurities degrading the oil further. Add to it excessive heat, & can you honestly say that your cars cooling system is working in such a way that its doing all it can to protect your investment?? If you think consistently running an engine with 220*+ oil temps doesn't have an effect on internal parts & doesn't cause premature wear, well I'm not sure what to tell ya.
 

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Discussion Starter #14
Scout,

Yeah, sounds like you've got an air pocket in your heater core. To expand on what Mtyler told you to do about lifting the front in the air, its also a good idea to get an spill-free funnel. You take the radiator cap off, attach the funnel (it has different adaptors that come with it) then after the coolant has gotten up to running temp you run the rpm at about 2k for about 20 seconds. Do this several times & add coolant as needed. That'll help push the air through the system. The funnels are about $30 off amazon.
Or if funds are limited, aren't they always, you can overfill the reservoir about an inch or so. Then run the truck for a couple days & keep watch on the level & add as needed. Also, after the truck has cooled down for awhile you can pop the top on the reservoir & 'burp' it that way. Just be sure to open the cap slowly so the coolant doesn't come rushing out & get on you then possibly burning you. Theres several ways of 'burping' your cooling system. It all depends how comfortable you are on doing it which way.



Mtyler11,

Ahhhh, ok. Gotcha. That makes sense about the speedo. Thank you! :)
 

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I'm curious where you have your info from that the motor needs to run hotter...
The normal operating temperature for most engines is in a range of 195 to 220 degrees Fahrenheit, though most dashboard temperature gauges don't show an exact temperature. Instead, there are typically markings for cold and hot on the edges of the gauge and a normal range in the middle. In most vehicles, the temperature needle will be at or near the center when the engine is at normal operating temperature, which usually takes at least a minute or two to reach after starting a cold engine.
Read more at https://www.cars.com/articles/should-i-worry-about-how-hot-my-engine-is-running-1420680334271/#Yfa822KLkGbf3JXZ.99
The Factory Service manual says:

Thermostat opens at 177-182 deg F
Thermostat full open at 203 deg F

Water control valve:

Opens: 200-206 degF
Full open: 226 degF

The hotter the internal temp of the motor, the more efficiently it burns fuel.

Any more questions?
 

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The Factory Service manual says:

Thermostat opens at 177-182 deg F
Thermostat full open at 203 deg F

Water control valve:

Opens: 200-206 degF
Full open: 226 degF

The hotter the internal temp of the motor, the more efficiently it burns fuel.

Any more questions?
water valve is only for the 4banger... Yes the tstat is a 195deg unit, but that doesn't mean its optimum. OEMs run the engine at ~195 for emission reasons, not for efficiency. gas engines are most efficient when in Open Loop and air is as cold as possible. The intake track is long (for the air) but the fuel track is short (injected just before the valve). The hotter the engine, the hotter the air. The fuel isn't there long enough to heat up. ACTUALLY the action of injecting the fuel COOLS the air charge. This is one reason racers have a cup that the fuel line runs through as a coil that you add ice to.

There's a reason NISMO has a cold tstat. Its for performance. and it is measureable. As the engine gets hotter, the more it has to de-fuel to prevent pre-detonation. This is the #1 reason you want a colder motor. #2 is for denser air. denser air has more O2. You get denser air with colder air.
The ECM during Open Loop (when it uses data from IAT, O2, MAF sensors) adjusts for the efficiency (complete burn).
As long as you are hot enough to stay in Open Loop (above 158deg F) thats as hot as you need.
 

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Most Efficient Internal Combustion Engine - HCCI

TLDR cooler combustion temps are better (to a point)... keep the motor cool for power... as long as its coolant temp is ~155 to run in open loop so ECM can do its job (optimize power/efficiency/emissions)

Also, Nissan is working on a new motor design... and GM did it first...
 

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Most Efficient Internal Combustion Engine - HCCI

TLDR cooler combustion temps are better (to a point)... keep the motor cool for power... as long as its coolant temp is ~155 to run in open loop so ECM can do its job (optimize power/efficiency/emissions)

Also, Nissan is working on a new motor design... and GM did it first...
I hope it's not a "variable displacement" motor, that thing scares me. Too many moving parts.
 

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I hope it's not a "variable displacement" motor, that thing scares me. Too many moving parts.
everything I've seen says 'no' to variable displacement & everything done with variable compression using VTEC (variable valve timing). So now your VTEC will be VTEC-ier!
 
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