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+categories = ["vehicle"]
+date = 2026-01-06T16:00:00Z
+description = ""
+draft = false
+slug = "2026-01-06-replace-thermostat"
+title = "🌡️ Replacing Thermostat Housing Assembly"
+author = "nicholas"
+++
+
+The engine coolant temperature gauge reports temperatures that are too low. The engine never reaches the proper operating temperature. The cabin air heating system produces only slightly hotter-than-ambient air. The upper radiator hose begins to warm immediately on starting the car. These are all symptoms of a thermostat that is stuck in the open position. I bought a new one from automotive store.
+
+
+## 🛠️ Parts and equipment
+I need a few tools and the replacement part:
+
+- Murray Plus 221 Degree Thermostat Housing - 73021
+- car ramp (2)
+- wheel chocks (2)
+- torx E10 socket
+- torx T15 drive bit
+- hex 10mm socket
+- flat head screwdriver
+- phillips head screwdriver
+- ratchet
+- clamp pliers
+- hook pick
+- drain pan
+- DEX-COOL engine coolant
+- automotive trim removal tool
+- silicone tube (3/8 in ID)
+
+{{< image 
+    src="images/oreilly-thermostat-part.png" 
+    caption="Thermostat Housing Assembly" >}}
+
+
+## ⚙️ Process
+I need to drain the coolant system first, then I can replace the thermostat, and finally refill the coolant.
+
+
+{{< image 
+    src="images/coolant-system-diagram-original.png" 
+    caption="Coolant System Diagram" >}}
+
+### drain coolant system
+- place car onto ramp, place wheel chocks under rear wheels
+- remove negative battery terminal clamp, disconnect
+- remove engine splash shield
+- place silicone drain hose over petcock nipple, place catch pan under hose
+- unscrew coolant reservoir cap
+- open petcock valve, drain coolant
+- close petcock valve, remove tube, store used coolant
+- replace splash shield
+
+### replace thermostat housing assembly
+- remove air filter hose
+- remove positive crank ventilation hose
+- remove sensor connector
+- remove upper radiator hose
+- remove thermostat housing assembly
+- install replacement thermostat housing assembly
+- replace all removed components
+
+I refill with new coolant and purge the coolant system of air.
+
+✅ Done.