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How closely do you watch your temperature gauge?

post #1 of 24
Thread Starter 

A little story.... I was driving my G35 around Sunday evening and it started getting cold so I turned on the heat, but no heat was coming out.   The engine was warm and the temp gauge showed a normal reading, so immediately that seemed odd.   I cranked the heat all the way and the engine temp shot way up.   I pulled over and the let the engine cool down a bit, then was able to drive home slowly with a light throttle keeping the engine in an acceptable, but still high range.

 

Turns out the Nisson dealer where I had service done a month ago screwed up.   My G35 engine (same V6 as in several Nissans) is notoriously difficult to bleed the air from the cooling system after changing the coolant.  Part of the process of bleeding the air is turing the heat on high, which never happened a month ago when I had my coolant changed.  If there is air in the system the coolant won't circulate.  The engine will overheat and likely cause extensive damage.  If I hadn't quickly noticed the temp shoot up, I likely would have blown a head gasket causing several thousand dollars damage... and never know why.

 

So, how closely do you watch the temperature gauge?   Would you notice if your car is overheating before damage is done?   I checked, and all three of our cars have temp gauges and no idiot lights.  I like having gauges, but wish there was an idiot light too just in case.

post #2 of 24
Second most important gauge next to the Pyrometer during operation.
post #3 of 24

Had a Honda motorcycle dealer do the same thing to my 750 Honda Interceptor back in the day (not turn on the heat, just didn't put enough coolant back in to trigger the fan thermostat:nono:.   

 

I keep a pretty close eye on the temperature guage, and I don't rely on the guage alone.

post #4 of 24
I use a ScanGauge for my truck. It plugs into the diagnostics port and reads what the OBDII (OnBoard Diagnostics II)is reading, which are the various sensors that trigger your gauges and the innocuous check engine light.

Here it is at startup - I have selected water (coolant) temp (87) intake air temp (58), charging system voltage, and the blank one would be average calculated fuel economy (you pick your engine and enter actuals for awhile and it learns how your throttle affects mpg quite accurately) because I haven't driven anywhere yet.



The problem with dash gauges is they are typically set to thresholds. The needle will sit in one place as the temp moves within the threshold, and then will suddenly spike. The system knows exactly what the temp is, but you can't see it climb until the trigger point.

What's cool about the Scanguage beyond this is that it will read check engine codes and you can look them up online. My Cruiser pops emissions codes in the summer, probably because of our shitty ethanol gasoline mixes and higher temps, and I can press a few buttons and clear the codes. I don't have one in my Nissan minivan as it is a bit of overkill, but it is eye opening to see the degree to which your gauges mislead until they sound an alarm.
post #5 of 24

Hardly ever..and I was a mechanic for 10 years!  :D

post #6 of 24

I had a Ford Escort (awful car...) that broke down when the temperature gauge which had broken led to a cracked a head gasket.  The thing needed a new engine.

 

Craziest part was... I was winter camping in Jackson Hole and on the morning the car overheated without me knowing it it was -10 outside.  Made for an interesting morning (January 1, 2002).

post #7 of 24
Quote:
Originally Posted by tball  Part of the process of bleeding the air is turing the heat on high, which never happened a month ago when I had my coolant changed.  If there is air in the system the coolant won't circulate.  

Standard procedure for anybody who knows what they are doing. I wonder how many customers poached their engines thanks to this persons lack of skill. Time for a new dealer.

post #8 of 24
Thread Starter 
Quote:
Originally Posted by NayBreak View Post

I use a ScanGauge for my truck. It plugs into the diagnostics port and reads what the OBDII (OnBoard Diagnostics II)is reading, which are the various sensors that trigger your gauges and the innocuous check engine light.
 

 

Great idea.   I've just gone to Autozone to have codes pulled, but never thought about using it to monitor operations.  ScanGauge doesn't have alarms, but the cheaper UltraGauge does.  Not sure my wife will want to drive around with that plugged in, though.   I probably shouldn't say it, but I'm more worried about her watching the temp gauge.  Good chance we'd be looking at a new engine or car if she was driving when it overheated.

 

Quote:
Originally Posted by NayBreak View Post

The problem with dash gauges is they are typically set to thresholds. The needle will sit in one place as the temp moves within the threshold, and then will suddenly spike. The system knows exactly what the temp is, but you can't see it climb until the trigger point.
 

 

I didn't realize gauges are so dumbed down until this incident.   I thought the gauge was broken or my engine was toast because it shot up so quickly, but after a bunch of research realized that's the way they designed it :rolleyes

 

Quote:
Originally Posted by river-z View Post
 

I had a Ford Escort (awful car...) that broke down when the temperature gauge which had broken led to a cracked a head gasket.  The thing needed a new engine.

 

 

Bummer.   The potential for a broken gauge is another reason to have an idiot light in addition to the temp gauge.   I didn't realize the check engine light won't even come on if a car is overheating, and can't imagine why not.  I read the owners manuals of our G35, Tundra and MDX and none will indicate overheating other than the temp gauge.  The computer knows the car is overheating, why not throw the light on too????

 

Being an idiot, I did run out of gas once when my idiot gas light was broken.  The gauge was working fine but the gas light went bad.... so I didn't know when to fill up with gas and ran out.  :)

 

Given the potential catastrophic damage of overheating, I wish cars had a over-temp light in addition to a gauge, just like the low gas indicator light.

post #9 of 24
^^^that's interesting about the check engine light. I had a moron experience just a couple of weeks ago when I was changing the alternator on my wife's 2007 Quest and had to pull the entire radiator to get to it, so full coolant drain required. I hooked up the lower main coolant hose checking for fitment on reassembly and forgot to re-clamp it.

Fast forward three days, taking the kids to get flu shots, and this guy in another car is waving frantically at us and finally just pulls in front, stops, and tells me I have coolant pouring out. Temp gauge had just started to spike. I Idle it to the next intersection, pull off and look underneath, figure a hose blew, and decide to drive very slowly the one mile to the doctors office where there is also a gas station.

Temp stays high on the gauge, but no overheating. Check engine comes on. Buy some pliers and distilled water at Albertsons, coolant at the gas station, and basically get lucky and just put it all back together. But the system could somehow register the coolant loss I guess since it didn't overheat.

On a side note, I hadn't done a coolant flush before and tried to read up on various Nissan forums on bleeding. I came to the conclusion that running the heater is just to get the system to open and flow while in idle, but in a closed system it will exchange air for coolant in the reservoir, and the idea was just keep the front end up (using ramps I use for oil changes) during the initial radiator fill and then keep refilling the reservoir upon cooling after a short drive. Took 2 or 3 times to keep the reservoir from draining as the air/coolant exchange completed.

I have zero expertise here, but seems no way you can complete that process without several cycles. It doesn't strike me as bleeding as much as cycling the system to open without hitting extended running temps for a period of time and risking air pocket driven coolant detonations you don't want, and then cooling for the air/coolant exchange in the reservoir.

I had to refill the reservoir several times, and if that is typical then any shop could easily send you on your way with a properly filled reservoir that drains at next cool down. And then you don't check.

I don't let shops work on my cars for the basics given the potential issues like this, but having done one, a coolant drain and refill is so simple and yet requires multi-cycle observation that I wouldn't trust any shop for that job. Once done, the only remaining issue in my mind is checking the hoses periodically for signs of cracking, something else none of us do along with not paying attention to drive belts. But seeing is believing and you know when the system has no air left.

I could be totally wrong about most of this, just thought it was interesting having just been through something relative with my Nissan. One other thought was that the coolant at 100K was like new. I'm not sure that opening up the system and risking stuff like this is worth the idea that these modern fluids really break down. I had to do it for an unrelated failure, but I wouldn't touch it for maintenance having been in there and seeing zero contamination without some other symptom.
Edited by NayBreak - 10/14/14 at 9:08pm
post #10 of 24
Thread Starter 

^^^ Interesting your check engine came on when overheating.  OK, I could be wrong about the check engine light not coming on.  I hope so.  

 

I was basing that on one of the owners manuals I read saying something like "the temperature gauge is the only indication of the engine overheating," and the other owners manuals never mentioning the check engine light as an indication of overheating.   I can't imagine why the computer wouldn't turn it on when overheating, so I'm probably wrong... but not going to count on it!  

 

On the G35 there is a bleeder valve on a hose back by the firewall to help get the air out of the cooling system.  The recommended procedure does require running the engine then cooling it down and refilling it, which I also wonder if shops take the time to do.  Clearly mine didn't.  

 

I'm done with the Nissan dealer.  Here's hoping the new Infiniti dealer does good work, as that's where it's going next.  The other Infiniti dealers are too far away.  I'd rather just pay someone to do it right rather than figuring it out myself.  I did fix a broken transmission and put a new engine in my RX-7 back in the day.  Since then my cars have been so reliable they haven't needed much more than routine maintenance, so I'm willing to pay the dealers to get it done right, or that was the idea!

post #11 of 24
Nissan does have a specific check engine code for overheating - P1217. So it should light up like mine did.

post #12 of 24
Quote:
Originally Posted by tball View Post

I'd rather just pay someone to do it right rather than figuring it out myself.  I did fix a broken transmission and put a new engine in my RX-7 back in the day.  Since then my cars have been so reliable they haven't needed much more than routine maintenance, so I'm willing to pay the dealers to get it done right, or that was the idea!

Ummm....

1) takes pets inside (sweet toxic coolant);
2) drives car up on maintenance ramps, blocks rear tires;
3) opens beer;
4) unscrews coolant drain bolt, drains coolant, re-tightens coolant drain bolt;
5) seals drained coolant in proper container and places out of reach of children / pets for disposal;
6) dilutes any coolant spill spots with water after wiping up;
7) washes hands, drinks beer;
8) opens radiator valve and refills radiator and reservoir;
9) washes hands, drinks beer;
10) turns car on with heater on high heat (outside air);
11) drinks beer;
12) looks at watch, needs to run for 10 minutes. Looks at radiator coolant level through fill plug;
13) finishes beer;
14) opens new beer;
15) adds coolant to radiator as necessary;
16) drinks beer (is all that constant hand washing really necessary at this point)?
17) maybe this could go for 15 minutes;
18) drinks beer;
19) 20 minutes now;
20) finishes beer;
21) radiator full, reinstall radiator cap;
22) unblock rear tires, back off ramps;
23) clean up;
24) open new beer;
25) let pets back out;
26) finish beer;
27) drive and cool down the next day until the reservoir levels and temp gauge are stable.

You are missing a clear opportunity to turn a one beer job into a three beer job in 27 simple steps biggrin.gif
post #13 of 24
Thread Starter 

^^^ Three beers is a great argument for DIY... but, I have an ever so slight preference for riding my bike.  So off to the dealership goes the car.   I do (did) enjoy working on cars.   Lots of things I like more, though.    

 

Back on the temp gauge and check engine light: after some googling, I do think the check engine light would have come on if my G35 had really overheated.   I'm probably just lucky I noticed the gauge before it got to that point   I read many stories online of the same scenario as mine ending up with a blown head gasket.  Once your check engine light comes on it may be too late.   We really need to keep an eye on our temp gauges.

post #14 of 24
Yep. And realize the margin of error to major damage with these threshold calibrated gauges is incredibly narrow in a cooling system failure. I think it is on the level of pure dumb luck to see it climb in those precious few seconds.

Which is why I question opening up the system in the first place just for a fluid change. Shops push flushing the system because they can charge more, but that can dislodge stuff that would otherwise stay put, making you think you need to flush more often. May not be worth the risk of things like blown head gaskets to flush perfectly clean functioning fluid.
post #15 of 24

The wife drives a 2008 Audi A3 - just old enough to start exhibiting signs of "German Engineering". Had to replace the compressor on the AC system and when we got it back from the shop the AC was fine but the temp gauge wasn't working. Took it back the next day and Art the mechanic replaces the sender. A week later it's not working again, I take it back to Art and it works fine when he's driving it. I'm growing less enamored of Art's diagnostic skills so I take it Mickey across town. He says the thermostat assembly controls the gauge and needs to be replaced ($350). The car runs fine, doesn't overheat.

 

So yeah, I watch my temp gauge like a hawk - when it's working!

post #16 of 24

I have the opposite problem with my temperature gauge. I've never noticed it overheating, but I've noticed on a cold day it goes down when I am going downhill for long stretches. So when I get to the bottom of a mountain pass, my heater is blowing cold air and my temperature gauge is buried below the C. It goes right back up when I get to level ground or an uphill section. Weird, right? Anyone know what is going on here?

post #17 of 24
Thread Starter 
Quote:
Originally Posted by CluelessGaper59 View Post
 

I have the opposite problem with my temperature gauge. I've never noticed it overheating, but I've noticed on a cold day it goes down when I am going downhill for long stretches. So when I get to the bottom of a mountain pass, my heater is blowing cold air and my temperature gauge is buried below the C. It goes right back up when I get to level ground or an uphill section. Weird, right? Anyone know what is going on here?

 

Um, Physics.  Your engine isn't doing much work going down a big hill so it's your coolant is getting cold.   It all makes sense to me.  If it's really, really cold and you are going slow or are in neutral your thermostat could even close completely cutting off cabin heat.

 

Edit: Yeah, I used to know just how far I could coast coming down each Colorado pass before I had to put it in gear and burn gas.   Your car will get cold.

post #18 of 24
Quote:
Originally Posted by river-z View Post
 

I had a Ford Escort (awful car...) that broke down when the temperature gauge which had broken led to a cracked a head gasket.  The thing needed a new engine.

 

Craziest part was... I was winter camping in Jackson Hole and on the morning the car overheated without me knowing it it was -10 outside.  Made for an interesting morning (January 1, 2002).


Extreme cold can freeze poor coolant even when the car is running,  then it causes the over heating.

Have helped out a few  people stuck because of that. Usually they had no idea their radiator froze but had no heat for a while before the car overheats.

No fun being stuck on a mountain pass in the middle of the night when it's below -35c and passing cars are very rare.

Even worse when your just wearing party dresses like one group.

.

post #19 of 24
Quote:
Originally Posted by CluelessGaper59 View Post
 

I have the opposite problem with my temperature gauge. I've never noticed it overheating, but I've noticed on a cold day it goes down when I am going downhill for long stretches. So when I get to the bottom of a mountain pass, my heater is blowing cold air and my temperature gauge is buried below the C. It goes right back up when I get to level ground or an uphill section. Weird, right? Anyone know what is going on here?


Your car is essentially idling going down those hills, and lots of air is passing through the rad, cooling it down.

Your car should have a thermostat, a spring loaded plate that closes off the coolant flow to the rad when the temperature is below a certain point.  Usually it lives where the upper rad hose attaches to the engine.  Sounds like your thermostat is reluctant to close once it's been opened.  Replacing a thermostat used to be dead easy, but the car engineers have been burning the midnight oil trying to make things more difficult.  What are you driving again?

post #20 of 24

Thanks Ghost- that makes sense. I don't even change my own oil. I'll have my mechanic check out the thermostat! I drive a 2002 Suzuki XL-7.

post #21 of 24

I read the thread title and initially thought it was about anger management strategies.

post #22 of 24

Does not sound like a thermostat; when these get stuck (in open position), the engine runs too cold.  When you cranked the heat on, the engine getting hot - also makes no sense to me; that should have caused the engine temperature to go down (not up).

 

It doesn't sound like a sensor either - these usually stick in one position (or don't register anything at all).

 

My guess is either low coolant, or bad coolant (you do know that coolant has to be replaced regularly, right?).  If you haven't replaced your coolant in  5 years, that should be a clue.  If you take off the radiator cap and it looks like dark roast, that's another clue, but could be worse (i.e., if it's  mocha - you have a cracked head and/or engine block).

 

Good luck.

post #23 of 24
Quote:
Originally Posted by qcanoe View Post

I read the thread title and initially thought it was about anger management strategies.

Well, sort of it is. At least when things go wrong.
post #24 of 24
Thread Starter 

Yeah, I've been known to overheat and blow a gasket on occasion.   Gotta let things idle more to keep the "check temper" from coming on :) 

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