How to Replace A Thermostat Housing

📋 Quick Facts

Plastic thermostat housings warp and crack with age - Chrysler Pentastar, Ford EcoBoost, GM Ecotec, and Audi/VW 2.0T are all known offenders. Replacement housing kits run $40-150. DIY is a 1-2 hour job. Many kits include the new thermostat preinstalled.

🛠 What You'll Need

• New thermostat housing assembly with new thermostat (thermostat housing kit on Amazon)
• New gasket or O-ring (often included) (thermostat housing gasket on Amazon)
• Fresh OEM-spec coolant (1-2 gallons) (coolant on Amazon)
• Drain pan (2-gallon) (drain pan on Amazon)
• Metric socket set and torque wrench (metric socket set on Amazon)
• Plastic gasket scraper (plastic gasket scraper on Amazon)
• No-spill funnel (Lisle Spill-Free funnel on Amazon)

✅ Before You Start - Checklist

• Park on level, solid ground (no slopes, no soft dirt)
• Engine is at the correct temperature (cold or warm as specified)
• All tools and parts on hand BEFORE you begin
• Owner's manual nearby for torque specs and locations
• Safety: gloves, eye protection, hood propped open

📝 Step-by-Step Instructions

1. Cold engine, hood up, battery negative offDisconnect the battery if the CTS sensor sits on the housing - prevents code storage.
2. Locate the thermostat housingFollow the upper radiator hose to the engine. The housing is the plastic or aluminum piece where the hose meets the block.
3. Drop the coolant level below the housingOpen radiator cap slowly. Drain via petcock or by pulling the lower radiator hose. Catch in pan - about 1 gallon.
4. Unplug all sensors on the housingCoolant temp sensor (CTS), sometimes a low-coolant sensor, and on some hybrids an electric thermostat connector. Squeeze locking tab, pull straight out.
5. Disconnect hoses from the housingUpper radiator hose, sometimes a bypass hose and heater hose. Loosen clamps, twist, pull. Cap with rags.
6. Unbolt the housing from the blockUsually 3-5 bolts (8mm, 10mm, or 13mm). Note lengths if different. Set aside in order - getting them wrong can punch through into a coolant passage.
7. Pull the housing straight offMay stick on old gasket - tap with a rubber mallet to break the seal. Do not pry with a metal tool against the aluminum sealing surface.
8. Remove the old thermostatNote orientation (jiggle pin up, spring/temp bulb toward engine). Most kits supply a new thermostat - discard old.
9. Clean the mating surface on the enginePlastic scraper only. Wipe with clean rag and brake cleaner. Aluminum gouges = guaranteed future leak.
10. Transfer sensors from old housing to new (if needed)If the new housing came bare, swap the CTS with a 19mm or 22mm deep socket. Apply a dab of thread sealant if the threads are not pre-coated.
11. Install new thermostat in the housingMost aftermarket kits ship with the thermostat preinstalled. If yours did not, seat it in the housing recess - jiggle pin up.
12. Place new gasket or O-ring on the housingO-rings: seat fully in the groove. Paper gaskets: dry on, no sealant needed.
13. Bolt the new housing to the blockHand-start all bolts first. Torque in a cross pattern to FSM spec (typically 80-100 in-lb or 8-12 ft-lb).
14. Reconnect hoses, clamps, and sensorsMatch your photos. Snap connectors until they click.
15. Refill coolant via no-spill funnel and bleedHeater full hot, engine on with funnel, top off as level drops. Squeeze upper hose to burp air. Drive 10 miles, recheck cold the next morning.

✅ After You Finish - Verify Checklist

• No tools left in the engine bay or under the car
• Test the system you worked on (start, drive, check, etc.)
• Look for leaks or drips after 5 minutes of running
• Record the date and mileage in your service log
• Recycle or properly dispose of any old parts/fluids

🔗 Related Guides

❓ Frequently Asked Questions