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Probably not a problem. Really Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Wed, 23 Jan 2008 14:02:00
In Reply to: T-stat installed, temp wanders, TomA, Fri, 18 Jan 2008 20:20:11 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Let me guess - when the car is first warming up, you'll see the temp gauge go up and up, and then somewhere above 9;45, it suddenly drops. Just a few seconds. Then it creeps up again, and drops down. The swings gets smaller and smaller as the car warms up. You don't notice it much when the car is warm.
Normal. Really. When the car is cold, the radiator is full of cold coolant - maybe 30 degrees on a typical morning, colder even, and your brandy-new thermostat is shut tight. The engine starts to warm up, and the nice new thermostat stays nice and tight. The engine temperature climbs. When the temperature at the thermostat gets warm enough (typically about 180 F), it opens; this pushes a chunk of cold coolant (30 degrees) from the radiator into the engine; it sweeps by the coolant sensor on the way to the thermostat. Yes it has picked up heat from the engine, but it's still colder than what was there. The temperature at the sensor drops like a rock. The thermostat sees the colder temperature coolant and shuts. And the cycle continues until the engine/radiator temps start to equalize. When the engine is cold, the difference between the coolant in the engine and the radiator can be 150 F or more; once it's warmed up, there is maybe a 30 degree difference.
Why didn't you see this before? With your old, slow, leaky thermostat? The one that didn't respond quickly, and that didn't shut that tight?
When I replace a thermostat, I see this happen about 50% of the time. And then after a couple of weeks, the new thermostat quiets down and you don't see the big swings. And about half the time, the new thermostat looks just like the old one.
As to an air bubble, if you did put the thermostat in upside down, it will still bleed, just not as effectively. You'd probably notice it as a reduction in heat, because the bubble will lodge in the heater core - the top of the system.
If you're getting enough heat, you can hold off on going in after the thermostat. I'll bet that by the time it gets warm, you won't bother.
posted by 192.249....
, Wed, 23 Jan 2008 14:02:00 <-- Viewing This Message
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