1985-1998 [Subscribe to Daily Digest] |
 | [Main 9000 Bulletin Board | BBFAQ |
Prev by Date | Next by Date | Post Followup ]
Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
Not much Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Fri, 28 Nov 2008 22:17:38
In Reply to: Low temp thermostat. . . ., David W, Thu, 27 Nov 2008 08:13:45 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The advantage of an 82C thermostat is that the engine can run a little cooler. This will have some advantage in really hot climates. There is also the psychological advantage that there is more 'headroom' between where the engine is running and overheating. I say psychological, because it isn't much help. If the car is going to overheat due to a problem, starting 7 degrees (C) cooler means about half a minute more time before you overheat.
Downsides? Less cabin heat, but you probably won't notice it unless you live where it regularly gets below 0 degrees F. Two bigger ones - the engine runs cooler. Yes, that seems like one. The engine was designed for 89C. So you'll be running wider clearances and the engine won't be as efficient - there will be a gas mileage hit. Enough to notice? Good question. Also, when a car sits, the oil absorbs water. Running the engine heats the oil, which boils off the water. If the engine is running cooler, it takes longer to boil off the water. If you typically take 20 minute or longer trips, the water will boil off. If you take short trips, the car won't warm up as much, as hot, and as long, and you'll have more water in the oil. See, two downsides.
Also, just changing the thermostat doesn't make the engine run cooler when you need it most. Huh? All the thermostat does is open to port hot coolant to the radiator. When you're driving along at speed, the radiator can dispose of that waste heat in the strong airflow. At that time, the engine will sit at whatever temperature the thermostat is. Nice. But when you come to a stop, the airflow also stops, and the radiator can't dispose of all the heat load. When the coolant temperature gets high enough, the radiator fan kicks in. On older cars, that is determined by a switch on the radiator. On the newer ones (like your 97), it's based on the coolant temperature. So even with a 82C thermostat, the coolant is going to have to get hot enough to turn on the radiator fan. With older cars, going to a 82C thermostat didn't do much without changing the radiator fan switch to 82C also. Otherwise, the thermostat just sits wide open and the engine just gets hotter. On the newer cars, the trip is built into the engine control (EDU, actually), and isn't so easily changed.
Bottom line, it might be of some marginal use in very hot climates. Otherwise, it is of questionable value. The good news is it probably won't hurt. However, if the car were used primarily for short trips, I would advise against it. The water boil-off curve (versus time) isn't pretty, and a cooler thermostat only makes it worse. Yes, I know the oil gets hotter than the coolant, but heat is heat.
posted by 76.243.122...
, Fri, 28 Nov 2008 22:17:38 <-- Viewing This Message
, Thu, 27 Nov 2008 15:43:08
No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.
 |
 |
 |
 |
 |
