1
00:00:00,560 --> 00:00:03,320
Speaker 1: Welcome to brain Stuff from how stuff Works dot com

2
00:00:03,640 --> 00:00:07,840
Speaker 1: where smart Happens. Hi. I'm Marshall Brain with today's question.

3
00:00:08,200 --> 00:00:11,520
Speaker 1: How does the thermostat in a car's cooling system work?

4
00:00:12,200 --> 00:00:15,800
Speaker 1: Any liquid cooled car engine has a small device called

5
00:00:15,840 --> 00:00:19,000
Speaker 1: the thermostat that sits between the engine and the radiator.

6
00:00:19,400 --> 00:00:22,480
Speaker 1: The thermostat and most cars, is about two inches in diameter.

7
00:00:23,000 --> 00:00:25,639
Speaker 1: Its job is to block the flow of coolant to

8
00:00:25,680 --> 00:00:28,639
Speaker 1: the radiator until the engine is warmed up. When the

9
00:00:28,680 --> 00:00:32,480
Speaker 1: engine is cold, no coolant flows to the radiator. Once

10
00:00:32,520 --> 00:00:35,560
Speaker 1: the engine reaches its operating temperature, which is usually about

11
00:00:35,600 --> 00:00:39,839
Speaker 1: two degrees fahrenheit, the thermostat opens by letting the engine

12
00:00:39,840 --> 00:00:43,400
Speaker 1: warm up as quickly as possible. The thermostat reduces where

13
00:00:43,760 --> 00:00:47,199
Speaker 1: deposits and emissions. If you ever have the chance to

14
00:00:47,320 --> 00:00:50,920
Speaker 1: test the thermostat, it's an amazing thing to watch because

15
00:00:50,960 --> 00:00:53,840
Speaker 1: what they do seems impossible. You can put one in

16
00:00:53,880 --> 00:00:56,440
Speaker 1: a pot of boiling water on the stove. As it

17
00:00:56,520 --> 00:00:59,880
Speaker 1: heats up, its valve opens more than an inch. Apparently

18
00:01:00,040 --> 00:01:02,720
Speaker 1: I magic. If you'd like to try it yourself, go

19
00:01:02,800 --> 00:01:04,800
Speaker 1: to a car part store and buy one for a

20
00:01:04,840 --> 00:01:08,000
Speaker 1: couple of bucks. The secret of the thermostat lies in

21
00:01:08,120 --> 00:01:11,920
Speaker 1: the small cylinder located on the engine side of the device.

22
00:01:12,480 --> 00:01:15,160
Speaker 1: This cylinder is filled with a wax that begins to

23
00:01:15,240 --> 00:01:19,240
Speaker 1: melt at about a hundred eighty degrees fahrenheit. Different thermostats

24
00:01:19,280 --> 00:01:21,760
Speaker 1: open at different temperatures, but a hundred eighty degrees is

25
00:01:21,760 --> 00:01:24,560
Speaker 1: a common temperature for a thermostat. To open it, a

26
00:01:24,760 --> 00:01:28,440
Speaker 1: rod connected to the valve presses into this wax. When

27
00:01:28,480 --> 00:01:32,199
Speaker 1: the wax melts, it expands significantly and pushes the rod

28
00:01:32,319 --> 00:01:36,080
Speaker 1: out of the cylinder, opening the valve. The wax expands

29
00:01:36,080 --> 00:01:38,480
Speaker 1: so much because it's changing from a solid to a

30
00:01:38,520 --> 00:01:41,640
Speaker 1: liquid in addition to expanding from the heat. This same

31
00:01:41,680 --> 00:01:46,240
Speaker 1: technique is used in automatic openers for greenhouse vents and skylights.

32
00:01:46,280 --> 00:01:49,680
Speaker 1: In these devices, the wax melts at a much lower temperature.

33
00:01:50,280 --> 00:01:53,160
Speaker 1: Do you have any ideas or suggestions for this podcast?

34
00:01:53,560 --> 00:01:56,240
Speaker 1: If so, please send me an email at podcast at

35
00:01:56,240 --> 00:01:58,960
Speaker 1: how stuff works dot com. For more on this and

36
00:01:59,000 --> 00:02:01,200
Speaker 1: thousands of other top it's go to how staff works

37
00:02:01,200 --> 00:02:04,080
Speaker 1: dot com. MHM