Avoid overheating turn off A/C signs

[kphoger]

Problems can ensue if the radiator fan isn't working ...

This.  A few years ago, my best friend's vehicle overheated in Mexico.  It's a 2005 Nissan Pathfinder (one of those "modern vehicles"), and he constantly does his own maintenance and parts replacements.  It ended up that the engine block cracked from the overheating, and he had to have the engine replaced (with a 2012 Nissan Xterra engine).  After it happened, he started thinking back, and he realized it had been a while since he'd heard the radiator fan kick on, so he suspects that may have been at least a contributing factor.  That fan not kicking surely wasn't due to lack of regular maintenance, and I'd be willing to bet that the large majority of drivers neither realize there are two fans under the hood nor listen for them.

[jander]

"Speed enforced by aircraft" .   On CA-25. In San Benito County. Because sure, San Benito County has the time, money, and aircraft to patrol that remarkably rural road.

[Max Rockatansky]

"Speed enforced by aircraft" .   On CA-25. In San Benito County. Because sure, San Benito County has the time, money, and aircraft to patrol that remarkably rural road.

At least trying to maintain 55 MPH or higher is actually kind of a challenge (a fun one) on 25 from 198 to J1. 

[kphoger]

"Speed enforced by aircraft" .   On CA-25. In San Benito County. Because sure, San Benito County has the time, money, and aircraft to patrol that remarkably rural road.

I saw those signs growing up in rural Kansas.  Are/were they not a nationwide phenomenon?

[Max Rockatansky]

"Speed enforced by aircraft" .   On CA-25. In San Benito County. Because sure, San Benito County has the time, money, and aircraft to patrol that remarkably rural road.

I saw those signs growing up in rural Kansas.  Are/were they not a nationwide phenomenon?

It's a dig at how silly the expense of wasting money on such a rural and lightly traveled state highway would be.  25 would be high on the list of my favorite desolate state routes, very scenic but you are on your own.  Amusingly 25 is called the Airline Highway.

[J N Winkler]

This.  A few years ago, my best friend's vehicle overheated in Mexico.  It's a 2005 Nissan Pathfinder (one of those "modern vehicles"), and he constantly does his own maintenance and parts replacements.  It ended up that the engine block cracked from the overheating, and he had to have the engine replaced (with a 2012 Nissan Xterra engine).  After it happened, he started thinking back, and he realized it had been a while since he'd heard the radiator fan kick on, so he suspects that may have been at least a contributing factor.  That fan not kicking surely wasn't due to lack of regular maintenance, and I'd be willing to bet that the large majority of drivers neither realize there are two fans under the hood nor listen for them.

This is one reason I get nervous about automakers eliminating temperature gauges (the 2009 Honda Fit in the family fleet doesn't have one).

Most newer cars have "soft start" fans that essentially run only as fast as needed to regulate coolant temperature to within about 10° F of a setpoint just above thermostat opening temperature.  To the driver it looks like the needle being pinned to just beneath the center of the gauge once the car is warmed up.  Without the ability to hear the fan, it can be hard to tell when the engine is laboring under thermal stress, but if the needle unpins and starts climbing, that is a pretty definite sign of problems.

Older cars, like my Saturn, tend to have "hard start" fans that run at full speed only when coolant temperature gets well above normal (thermostat opening plus ~30° F).  When a properly working fan triggers, the gauge needle swings rapidly back toward C until the thermostat is about to close, when the fan cuts out.  I have driven the Saturn for years and years without the fan coming on even once, only for it to run multiple times while I wait in traffic to cross the Bay Bridge or try to climb grades on the Pikes Peak toll road in top gear.

[kphoger]

This is one reason I get nervous about automakers eliminating temperature gauges (the 2009 Honda Fit in the family fleet doesn't have one).

Most newer cars have "soft start" fans that essentially run only as fast as needed to regulate coolant temperature to within about 10° F of a setpoint just above thermostat opening temperature.  To the driver it looks like the needle being pinned to just beneath the center of the gauge once the car is warmed up.  Without the ability to hear the fan, it can be hard to tell when the engine is laboring under thermal stress, but if the needle unpins and starts climbing, that is a pretty definite sign of problems.

Older cars, like my Saturn, tend to have "hard start" fans that run at full speed only when coolant temperature gets well above normal (thermostat opening plus ~30° F).  When a properly working fan triggers, the gauge needle swings rapidly back toward C until the thermostat is about to close, when the fan cuts out.  I have driven the Saturn for years and years without the fan coming on even once, only for it to run multiple times while I wait in traffic to cross the Bay Bridge or try to climb grades on the Pikes Peak toll road in top gear.

Temperature gauges aren't all the same anyway.  In the case of the Pathfinder, when that generation first came out in 2005, it had a real temperature gauge whose needle would move as the operating temperature fluctuated.  But so many people were taking their car to the mechanic for a supposed cooling system problem, when in fact nothing was wrong, that Nissan started installing a different type of gauge partway through the 2006 model year.  In the new gauge (the type both of mine mine had, which I've heard referred to as a "dummy gauge"), once the engine reaches normal operating temperature, the needle just pins to the midway point, no matter how the actual temperature fluctuates, until it reaches a near-critical threshold.  That way, people don't start freaking out at every little bump up and down of the needle.  In fact, I could often tell I was nearly out of coolant by the vents not blowing very much hot air well before I ever saw the needle move on the gauge.  And thus the downside is apparent:  by the time the needle would actually start to move upward, it would reach <H> within seconds, because the situation under the hood was so dire by that point.

[J N Winkler]

Temperature gauges aren't all the same anyway.  In the case of the Pathfinder, when that generation first came out in 2005, it had a real temperature gauge whose needle would move as the operating temperature fluctuated.  But so many people were taking their car to the mechanic for a supposed cooling system problem, when in fact nothing was wrong, that Nissan started installing a different type of gauge partway through the 2006 model year.  In the new gauge (the type both of mine mine had, which I've heard referred to as a "dummy gauge"), once the engine reaches normal operating temperature, the needle just pins to the midway point, no matter how the actual temperature fluctuates, until it reaches a near-critical threshold.  That way, people don't start freaking out at every little bump up and down of the needle.  In fact, I could often tell I was nearly out of coolant by the vents not blowing very much hot air well before I ever saw the needle move on the gauge.  And thus the downside is apparent:  by the time the needle would actually start to move upward, it would reach <H> within seconds, because the situation under the hood was so dire by that point.

This is interesting.  The first-generation Saturn S-Series had a similar issue in that small temperature changes would produce a lot of needle movement and the fan-on point corresponded to an indication just to the left of the red stripe next to H.  (This is the gauge I have.)  Many owners panicked, thinking their cars would boil over imminently in traffic.  The gauge was redesigned to reduce the amount of needle movement and to reposition the red stripe, but still gave a honest indication of temperature.  I can't say I think much of Nissan's approach.