25 Comments on “Auto Repair & Diagnostics : How to Know if a Thermostat Is Faulty on a Car”

• jeremy32100

  

  13 July, 2011, 11:01

  We have a 2000 Mercury Grand Marquis 4. 6 V8. 124k miles. Heat works great nice and hot but on cold winter days below 32 outside the temp gage stayed around the C mark, Check Engine light on P0125 code, now that its April almost May and Warm outside the temp gage needle finally moves to the normal operating tempeature. But when the AC the temp gage will drop a little. The check engine light went out on its own however it will still turn on sometimes,, any ideas on this? Thanks
• jeremy32100

  

  13 July, 2011, 11:25

  Hi, just confrim so are you saying if BOTH top and buttom radiator hoses are hot and about the same tempeature on both to the feel, does that mean the thermostat is working properly? Thanks
• RedBoiGoi

  

  13 July, 2011, 12:18

  @MrSPAXX7 Cool, you have some Vodka? Let’s partyyyy
• MrSPAXX7

  

  13 July, 2011, 13:00

  Hello, I’m Tom and I’m an alcoholic.
• alfqueiroz

  

  13 July, 2011, 13:00

  Very good quality information.
• xxdjcharlierockxx

  

  13 July, 2011, 13:09

  awesome. . . i know what i gotta do tomorrow! i know where to check it(i got no heat)now where to find the thermostat itself! i got a eagle talon btw. . . hey nice vid!
• z31man

  

  13 July, 2011, 13:41

  @frosty9595 o. 0 ! Not good. Man, i really don’t want to spend another hour putting my new one in. It does take forever to warm up now and gas mileage went to s#!t I guess. . . . . I’ll wait for the weather to warm up and stop being lazy. Thx.
• frosty9595

  

  13 July, 2011, 14:27

  @z31man It can do alot worse then no heat. Increased engine wear from metal not expanded from heat. . . . horrible gas milage from not going into closed loop. . . . ruined catalayic converter from not going into closed loop. . . . . and a laundry list of other things
• z31man

  

  13 July, 2011, 15:03

  Yeah, My top hose was HOT and the bottom was cold, or very cool. I just took my thermostat out to see if it’ll still overheat. Waiting for the sealant to set right now. If it still overheats, it’ll probably be my water pump. If it doesn’t, I can live with my car taking forever to warm up. I Live in Florida, so the heater is almost useless.
• Ooomwizard

  

  13 July, 2011, 15:27

  @MakeGlovesNotWars Could be a clogged heater core, or, the underdash vent system isn’t opening up to allow cabin air to flow through. If you can pull off both in/out hoses from the heater core (from the far ends) and blow on one end you can tell if it’s clogged. As for underdash vents you have to “dive in. ” (Could be a vacuum line problem. ) GL!
• Ooomwizard

  

  13 July, 2011, 15:45

  @cannonseeker Sounds like a blown head gasket. Does the radiator fill hole smell like exhaust? If so, that’s your problem. GL!
• MakeGlovesNotWars

  

  13 July, 2011, 16:06

  Hey there, I have a 1962 Willys Wagon. Both hoses are warm, the truck doesnt overheat, and it still blows cool air. I made sure there was no air in the system as well. Still thermostat, or clogged heater core(which I was told was new)
• macal38

  

  13 July, 2011, 16:26

  hello-i have a 1993 nissan quest-blows cold air only. radiator has enough anti-freeze. any ideas out their,i bought a new thermostat,have not change it yet. their is a bracket behind thermostat .
• LLeon252

  

  13 July, 2011, 17:05

  @cannonseeker
  Have you checked the radiator cap to make sure its good or right psi rating
• cannonseeker

  

  13 July, 2011, 17:08

  MY CAR IS A 03 VW GTI 1. 8T, IT OVERHEATS BUT THE ENGINE TEMP AND ALL HOSES ARE AT 195-210 DEGREES. ALL HOSES HAVE BEEN REPLACED, NEW THERMOSTAT, WATER PUMP, TIMING BELT AND NO PROBLEMS WITH MY RADIATOR. MY RESERVOIR IS RUNNING OVER FROM PRESSURE. I HAVE NO WHITE SMOKE COMING FROM MY TAILPIPE AND NO WATER IN MY OIL. I HAVE FAILED MY EMISSIONS INSPECTION. WHAT CAN BE THE CAUSE?
• nguyen2m

  

  13 July, 2011, 18:05

  @michaelheiland123654 The well fall out because he did not tie enough nut, low air pressure for hand gun.
• nguyen2m

  

  13 July, 2011, 18:34

  @pyaethiha You car radiator fan may not work properly when temperature going up.
  Check your radiator fan, make sure it running when engine is hot.
• dmdjm

  

  13 July, 2011, 18:53

  i agree. if the hose above is hot while the lower hose is cooler then most probably the coolant is not circulating in the engine. that makes real sense. very clear and easy to understand. good job, man! big help!
• johnredpath

  

  13 July, 2011, 18:56

  nice video dude very informative and clear. it helped me imenseley
• woopywoop24

  

  13 July, 2011, 19:05

  @pyaethiha check your radiator fan and thermo switch. . the thermo switch function is to detect the heat from the coolant inside the radiator, if the thermo switch is in good condition, it will trigger the cooling fan to cool the hot coolant inside your radiator.
• pyaethiha

  

  13 July, 2011, 19:42

  i have a 2003 eclipse gt with v6 engine. my car tends to overheat when driving slow or ideling in hot days. i changed thermostat already but the problem is still there. so what i had to do is turn the defrost on the let the fan run to cool the enging down.

  If you guys can help me fix this problem, please post solutions on here. thanks a lot.
• InitialDirt

  

  13 July, 2011, 19:56

  my car is a 1986 rx7
• michaelheiland123654

  

  13 July, 2011, 20:24

  My friend was driving a 1993 Explorer with no warning the wheel fell out yes old vechiles are scary, Pres Obama should take them out of the road like cash for clunker program!
• InitialDirt

  

  13 July, 2011, 20:51

  queer fuck
• InitialDirt

  

  13 July, 2011, 21:38

  its call a tow truck, and yes old cars are scary.