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Darn gauge Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Mon, 28 Mar 2005 05:27:07
In Reply to: Re: Cooling fan question..., Kyle Harris, Sun, 27 Mar 2005 17:57:24 Members do not see ads below this line. - Help Keep This Site Online - Signup |
There is a darn good reason why manufacturers put idiot lights in (no, this isn't a veiled insult) - Gauges cause them a world of trouble.
The 9000 has a repuatation for running hot. Actually, it has a reputation for a gauge that reads higher than people are used to from other cars.
The following is true for pre-96 cars:
The Saab temp gauge doesn't have numbers. It is also not linear - a 10 degree difference near the bottom is a lot more travel than 10 degrees near the top. So "10:00" is higher than 9:00, but is it bad? There is no standard for numberless temperature gauges - you can't compare a Saab temp gauge reading with a Toyota, or with anybody else.
Because there is a gauge, people can watch it, and quite often, obsess over it. What's a good value? It depends on a lot of things - If you're stuck in traffic, it is Normal for the gauge to be running higher. It will vary with outside temperature - believe it or not, the gauge can read higher if it is very cold outside. And with cars where the thermoswitch is in the radiator, there is at best a loose coupling between engine temperature and the fan coming on.
Folks like to obsess over it, and that's one reason people put in lower than stock thermostats and thermoswitches. Hey, running cooler must be right, right? Well, not necessarily. Lower engine temperatures mean lower efficiency, and the engine tolerances were designed for certain operating temps. Does that mean that running an 82C thermostat is a problem? Not really - I run them, because the 7 degree C difference between that and stock is pretty minimal.
Saab had so much problem with folks complaining about 'high' temp gauge readings that in later cars ('96 at least), they compensate the temp gauge reading for a bunch of things, like outside air temp and engine load. So on a '97 9000, you'll see a nice 8:30 reading, very solid. Does this mean that the engine temp is nice and low, and doesn't move? No, it means that the compensation algorithm, is taking out the variation that everyone worries about. If the engine temp goes high, the gauge will move up.
For those cars without temperature compensation on the gauge, the gauge can be very valuable, If you know what to IGNORE. It goes up when you're not moving much. It can go pretty high when stuck in traffic. As long as the radiator fan comes on, you're OK. When should you worry? When driving along the highway, with lots of airflow over the radiator, the temp gauge is creeping up near the red. Yes 9:00 is ideal, but not necessary. 9:15 isn't to worry about. On a 90 (F)day, with the A/C on, driving down the highway, you'll see higher readings than on a 45 degree day.
If the gauge gets into the red, that is a problem. If it gets a needle's width from the red, I'd be worried. If it were really near the red with lots of airflow over the radiator, I'd get the system checked. But Saab knew what it was doing when it set up the gauge, and if you aren't in the red, you aren't killing the engine.
posted by 192.249....
, Sun, 27 Mar 2005 17:36:28, Mon, 28 Mar 2005 05:27:07 <-- Viewing This Message
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