# Heat Stops Working When I am on the Freeway

**URL:** <https://community.cartalk.com/t/heat-stops-working-when-i-am-on-the-freeway/12236>\
**Category:** Maintenance/Repairs\
**Tags:** heating\
**Created:** [March 26, 2008, 10:37pm UTC](https://community.cartalk.com/t/heat-stops-working-when-i-am-on-the-freeway/12236 "2008-03-26T22:37:16Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![cyd000](https://avatars.discourse-cdn.com/v4/letter/c/34f0e0/32.png) [@cyd000](https://community.cartalk.com/u/cyd000)\
**Post date:** [March 26, 2008, 10:37pm UTC](https://community.cartalk.com/t/heat-stops-working-when-i-am-on-the-freeway/12236/1 "2008-03-26T22:37:16Z")

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The air will only blow warm when my car is left to idle for a period of time. If I start driving my temperature gauge drops clear down and I get nothing but cold air…so basically my heat only works when I am stuck in traffic.  
  
  
  
 Any ideas on what could be causing this?

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**Author:** ![Beadsandbeads](https://avatars.discourse-cdn.com/v4/letter/b/c57346/32.png) [@Beadsandbeads](https://community.cartalk.com/u/Beadsandbeads)\
**Post date:** [March 26, 2008, 11:20pm UTC](https://community.cartalk.com/t/heat-stops-working-when-i-am-on-the-freeway/12236/2 "2008-03-26T23:20:27Z")

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YOu need a new thermostat.

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**Author:** ![Docnick](https://avatars.discourse-cdn.com/v4/letter/d/ecae2f/32.png) [@Docnick](https://community.cartalk.com/u/Docnick)\
**Post date:** [March 26, 2008, 11:21pm UTC](https://community.cartalk.com/t/heat-stops-working-when-i-am-on-the-freeway/12236/3 "2008-03-26T23:21:43Z")

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Agree; most likely cause is a thermostat stuck in open position.

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**Author:** ![Joseph\_E\_Meehan](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/joseph_e_meehan/32/21_2.png) [@Joseph\_E\_Meehan](https://community.cartalk.com/u/Joseph_E_Meehan)\
**Post date:** [March 27, 2008, 11:58am UTC](https://community.cartalk.com/t/heat-stops-working-when-i-am-on-the-freeway/12236/4 "2008-03-27T11:58:08Z")

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Also a chance of air in the system, but I would bet on the thermostat.

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**Author:** ![cappy208](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/cappy208/32/31_2.png) [@cappy208](https://community.cartalk.com/u/cappy208)\
**Post date:** [March 27, 2008, 12:33pm UTC](https://community.cartalk.com/t/heat-stops-working-when-i-am-on-the-freeway/12236/5 "2008-03-27T12:33:55Z")

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thermostat costs around $12 gasket costs around $4 three or two bolts or nuts loosened up, and you pop off the thermostat housing, remove the old thermostat, pop in the new one (but you MUST put in the new thermostat the exact same way the old one came out; it IS possible to put them in backwards, then you will overheat)

trace the upper radiator hose from the radiator back to the engine. where the hose connects to the engine is the thermostat housing. that is what you remove and reinstall. once you get the thermostat housing off, you must clean up the surfaces (both the housing and the block) and use some permatex sealant to ensure the gasket seals.

this WILL let some antifreeze leak out. antifreeze IS toxic to pets, and it also attracts pets too. so clean up, catch all, and make sure you don’t harm the environment.