How accurate are our temp gauges?

[solsnowbarger]

Hey brothers, quick question.
I've been having a misfire in #2, ruled out all the common (small) stuff, and after a sophomoric effort at a compression test, I'm afraid I'm low on that cylinder. I don't trust my results enough to diagnose, for a number of reasons, so I'm gonna bite the $95 dollar bullet and have a very trusted shop do a leak down test for me to try and diagnose professionally.
I want to give them as much info as I can, and I want to say to them "heck no, my engine never overheated!" And as far as I've seen on my in-dash gauge, that's true. However, I've seen it mentioned that the original really isn't as accurate as it could be? If you all could assuage my fears a bit that'd be great... Or you can tell me my gauge is worthless and condemn me to a few sleepless nights. Either way Id appreciate it greatly. Thanks guys,
Solomon

 

[UnderFire]

Mine let me know as soon as I started to overheat and how hot it was getting as accurately as it could since it isn't actually labeled with temperatures.

 

[BrianSD_42]

It is accurate, usually - for what it does.

I believe at about 240F it leaves normal and ticks over to red.

Here are my 2cents (not a tech). Anything above 225 is HOT. Anything over 215 F should be investigated.

I don't know when engine damage occurs but I'd bet you are fine since you don't know of it overheating.

 

[solsnowbarger]

Awesome, that's all good to hear. Thanks much guys, this place is a haven of peace and knowledge in the rough seas of the Internet.

 

[Drcoffee]

Not at all. Its no better than an idiot light. My guage needle stayed in the exact same position from 160 to 212. It must use stages
1-100 no change
100-150 rise to normal
160-220 stays at center
240 + overheat
Dont trust it. If it rises above normal, you are in big trouble.

 

[gamefreakgc]

These 5VZ-FE engines can take a lot of abuse, so if it's never gone past normal you're good. It's sort of a "too late" kind of thing if it ever went to red though, so not super helpful.

On the predecessor engine in the 2nd Gen 4Runners, the 3VZ-E, if it went to red you might as well just pick up a new pair of head gaskets on your way home lol! Luckily I never had this issue but many did.

 

[volkinator]

Not at all. Its no better than an idiot light. My guage needle stayed in the exact same position from 160 to 212. It must use stages
1-100 no change
100-150 rise to normal
160-220 stays at center
240 + overheat
Dont trust it. If it rises above normal, you are in big trouble.

I was comparing the gauge to my SG2 on the way to work today. and I noticed this same thing, up to the 160* mark at least. It stayed right around 160-170 this morning (cold morning in MN) and was stuck right in the center. It's interesting why they did it that way, my GM actually had numbers on the gauge and was pretty accurate.

 

[JohnMc]

Lots of cars with temp gauges do this. Because people like to see a gauge, but if the needles is always moving up and down some with varying outside temps and engine loads, people get nervous and start bothering the dealership service department about the gauge acting funny.

So many car companies do this. They add circuitry between the temp sensor and the gauge that makes it act like an analog idiot light. And sometimes not just on temp gauges either, an old Bronco II I used to drive had an oil pressure gauge that basically acted the same way.

On my '93 Volvo there is a small circuit board in the instrument cluster that you could pull out and replace with a jumper wire - to send the sensor reading directly to the gauges. I've done that, and although it still doesn't have any numbers associated with it, it does move up and down to represent swings in coolant temp, instead of dumbly sitting at 'normal'. I have no idea if something similar could be done on a Toyota cluster or not. In the Volvo, it was probably an afterthought to add that circuitry in, so the gauge was already designed to accept the direct sensor signal. If the gauge was designed from the beginning to take a dumbed down signal it might not work properly with a real one.

 

[solsnowbarger]

Interesting, thanks for all the info brothers. I am a little encouraged that I never did see it very from its usual spot. I'll update Friday with my mechanics diagnosis and then begin the tedious journey of fixing whatever's wrong with it. I have maybe 101xxx miles on the runner, absolutely not a hint of rust, and I literally bought it from the proverbial old lady original owner in Texas, so if I can get this one (probably big) issue out of the way then I should be good to go for quite a while

 

[KidVermicious]

You don't have to have overheated to blow a head gasket. Sometimes they just go.

Don't borrow trouble, though, go get your leakdown and find out for sure what the trouble is first.

 

[Drcoffee]

I was comparing the gauge to my SG2 on the way to work today. and I noticed this same thing, up to the 160* mark at least. It stayed right around 160-170 this morning (cold morning in MN) and was stuck right in the center. It's interesting why they did it that way, my GM actually had numbers on the gauge and was pretty accurate.

I switched to an aftermarket t-stat and checked the coolant temp via the OBD2 port scanner. Installed the t-stat correctly but the temp rose to 212* so I replaced it with oem t-stat and the temp dropped to 186*. My dash gauge needle was in the same place thru a nearly 30* change of temp. You cannot rely on it.

 

[A.Wilson013]

Once while being an idiot in the sand I saw temps at around 210. Like [MENTION=78997]Drcoffee[/MENTION] said, the needle did not move.

The only time I ever saw it move was after doing my valve cover gaskets. My heater went from blowing lovely hot air, to pumping out cold air instantly, and the needle just barelllyyyy moved past the normal position. I immediately shut down the engine and addressed the issue (I had forgotten to clamp one of those coolant lines under the TB.)

I don't know how hot it was (before the days of my scan gauge), but it was apparently over 210.

 

[MandAtaco]

My 2000 never moves and I run between 190 and 210 depending on the situation.

I had a 96 that I tried to blow up about 3 years ago (long story), the Scan Gauge showed about 235+ but the dang needle never moved. That gauge is pretty much useless.

 

[TheDurk]

In the summer of 2010, my fan clutch went. I had been driving the NJ Turnpike with no problems and then hit the stop-and-go traffic on the upslope to the Lincoln Tunnel. Outside temp was 95°F. I saw a little steam out of the hood, but wasn't sure what it was. Gauge was to the right of center but not red. Turned off A/C. In another minute there was more steam and then the needle JUMPED into the red. I just couldn't stop for another 200 yards and the longest minute of my life as there was no shoulder and traffic was brutal going maybe 25mph. Pulled off at first exit, let it cool down, dumped my emergency drinking water bottle in, and went back home against traffic at speed with no issue.

So gauge was pretty much useless. Good news is it is five years and 50k later and I am thinking I dodged the bullet. No problems at all. Knock on wood. But red zone is not a guaranteed instant death.

 

[RedSled]

So with all this being said, i am wondering if there is a replacement ( aftermarket or ? ) that can be used that actually has degree readings, and maybe fit in the original spot?

 

[cashmoney]

It works for 99.9% of people on the road as does every other idiot gauge out there. I miss the days of being blissfully ignorant of vehicles. Thanks to forums like this I've become paranoid of every little temp fluctuation, every noise, every quirk that my vehicle does. There are days I stare at others in traffic and admire how they just get in a vehicle and drive it without ever worrying about anything and I sit back and wonder how it's possible for them to do that. I mean if they aren't monitoring every system in their car how can their car be expected to survive? How do they know that their alternator is charging half a volt low on this particular day? How do they know that they may have a weak plug or vacuum leak if they don't track their mileage? HOW DO THESE PEOPLE DO IT?!?!?!?

And after I get out of the looney bin I realize that it's because most people don't give a dang, most vehicles survive just fine without their owners knowing every single little thing that is going on with their vehicles, and that life goes on because the reality of the situation is that 99.9% of people will sell a vehicle inside of 5 years and so they never have to worry about it unless something actually happens which lets face it, 9 times out of 10 nothing does. Just think about people you know who drive their cars without fancy gauges or even a single clue about how a vehicle works and how their vehicles just keep chugging along with little to no issues. It's astounding really.

All of that to say that .1% of the owners of these vehicles are on forums such as this so they never get the fear of God put in to them about vehicle maintenance so instead of trying to second guess the engineers at Toyota why don't we all just sit back and relax and let the vehicle do its thing and quit worrying so much about them.

 

[RedSled]

It works for 99.9% of people on the road as does every other idiot gauge out there. I miss the days of being blissfully ignorant of vehicles. Thanks to forums like this I've become paranoid of every little temp fluctuation, every noise, every quirk that my vehicle does. There are days I stare at others in traffic and admire how they just get in a vehicle and drive it without ever worrying about anything and I sit back and wonder how it's possible for them to do that. I mean if they aren't monitoring every system in their car how can their car be expected to survive? How do they know that their alternator is charging half a volt low on this particular day? How do they know that they may have a weak plug or vacuum leak if they don't track their mileage? HOW DO THESE PEOPLE DO IT?!?!?!?

And after I get out of the looney bin I realize that it's because most people don't give a dang, most vehicles survive just fine without their owners knowing every single little thing that is going on with their vehicles, and that life goes on because the reality of the situation is that 99.9% of people will sell a vehicle inside of 5 years and so they never have to worry about it unless something actually happens which lets face it, 9 times out of 10 nothing does. Just think about people you know who drive their cars without fancy gauges or even a single clue about how a vehicle works and how their vehicles just keep chugging along with little to no issues. It's astounding really.

All of that to say that .1% of the owners of these vehicles are on forums such as this so they never get the fear of God put in to them about vehicle maintenance so instead of trying to second guess the engineers at Toyota why don't we all just sit back and relax and let the vehicle do its thing and quit worrying so much about them.

You know, your right. I think ill go for a ride.

 

[best4x4xfar]

It works for 99.9% of people on the road as does every other idiot gauge out there. I miss the days of being blissfully ignorant of vehicles. Thanks to forums like this I've become paranoid of every little temp fluctuation, every noise, every quirk that my vehicle does. There are days I stare at others in traffic and admire how they just get in a vehicle and drive it without ever worrying about anything and I sit back and wonder how it's possible for them to do that. I mean if they aren't monitoring every system in their car how can their car be expected to survive? How do they know that their alternator is charging half a volt low on this particular day? How do they know that they may have a weak plug or vacuum leak if they don't track their mileage? HOW DO THESE PEOPLE DO IT?!?!?!?

And after I get out of the looney bin I realize that it's because most people don't give a dang, most vehicles survive just fine without their owners knowing every single little thing that is going on with their vehicles, and that life goes on because the reality of the situation is that 99.9% of people will sell a vehicle inside of 5 years and so they never have to worry about it unless something actually happens which lets face it, 9 times out of 10 nothing does. Just think about people you know who drive their cars without fancy gauges or even a single clue about how a vehicle works and how their vehicles just keep chugging along with little to no issues. It's astounding really.

All of that to say that .1% of the owners of these vehicles are on forums such as this so they never get the fear of God put in to them about vehicle maintenance so instead of trying to second guess the engineers at Toyota why don't we all just sit back and relax and let the vehicle do its thing and quit worrying so much about them.

Well said sir. In my experience, I ventured into the red zone once upon a time in the desert running low on coolant. I had about 120k on the vehicle and am now at 162k. I had the A/C on and ambient temp was around 100° +. I watched as I hit the accelerator, the needle would move up and if I let off it would drop. Luckily, I had a big tank of water in the truck from the camping trip I had been on and filled up the coolant overflow and was fine the whole way back to Denver from western Utah (many miles, many big hills). After the trip I flushed and filled and have not seen anything of the sort since. So I have witnessed "some" sensitivity of the needle, and did not completely destroy anything.

 

[solsnowbarger]

Well said sir. In my experience, I ventured into the red zone once upon a time in the desert running low on coolant. I had about 120k on the vehicle and am now at 162k. I had the A/C on and ambient temp was around 100° +. I watched as I hit the accelerator, the needle would move up and if I let off it would drop. Luckily, I had a big tank of water in the truck from the camping trip I had been on and filled up the coolant overflow and was fine the whole way back to Denver from western Utah (many miles, many big hills). After the trip I flushed and filled and have not seen anything of the sort since. So I have witnessed "some" sensitivity of the needle, and did not completely destroy anything.

Agreed man. Before buying my Runner I had an old ES300 that I didn't do a damn thing to in the 5 years I had it, and I never once had a problem. Now, I did live in constant fear, listening to every noise and thinking to myself "the pedal feels different today, THE END IS NIGH!" I still have paranoid thoughts every time I start up, but now thanks to this forum I at least have a mild bit of confidence that whatever does go wrong, I might just be able to fix.

 

[gamefreakgc]

It works for 99.9% of people on the road as does every other idiot gauge out there. I miss the days of being blissfully ignorant of vehicles. Thanks to forums like this I've become paranoid of every little temp fluctuation, every noise, every quirk that my vehicle does. There are days I stare at others in traffic and admire how they just get in a vehicle and drive it without ever worrying about anything and I sit back and wonder how it's possible for them to do that. I mean if they aren't monitoring every system in their car how can their car be expected to survive? How do they know that their alternator is charging half a volt low on this particular day? How do they know that they may have a weak plug or vacuum leak if they don't track their mileage? HOW DO THESE PEOPLE DO IT?!?!?!?

And after I get out of the looney bin I realize that it's because most people don't give a dang, most vehicles survive just fine without their owners knowing every single little thing that is going on with their vehicles, and that life goes on because the reality of the situation is that 99.9% of people will sell a vehicle inside of 5 years and so they never have to worry about it unless something actually happens which lets face it, 9 times out of 10 nothing does. Just think about people you know who drive their cars without fancy gauges or even a single clue about how a vehicle works and how their vehicles just keep chugging along with little to no issues. It's astounding really.

All of that to say that .1% of the owners of these vehicles are on forums such as this so they never get the fear of God put in to them about vehicle maintenance so instead of trying to second guess the engineers at Toyota why don't we all just sit back and relax and let the vehicle do its thing and quit worrying so much about them.

Haha, that's totally it. I've been saying it for a while but no one gets it. I'm sad when a new member joins and is like "dude I need a new rad, tranny cooler, and have to flush my tranny right now" because they get scared from all the people who are freaked out about something bad happening to their 4Runner. When in reality, it rarely happens to anyone because Toyota did make a pretty good vehicle to begin with.

It's good to be aware of your vehicle and potential hazards to avoid, but there's a fine line between prevention and paranoia.