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Water necks, also called thermostat housings, are available in a variety of designs and finishes. Some include o-rings, so you can lose your factory gasket without losing any of your coolant.



What is a Water Neck?

Water necks and thermostat housings are the same thing. Replacing your water neck is as easy as replacing your thermostat. Polished aluminum and stainless-steel water necks add a little flash to that small block or big block you just finished rebuilding.

How do Water Necks Work?

The thermostat contained in the water neck opens as the engine reaches operating temperature. The water neck helps to hold the vehicle’s thermostat in place as it opens and closes to regulate the flow of coolant through your engine. The opening in the water neck created by the thermostat allows coolant to flow from the radiator back to the engine.

How are Water Necks Made?

Water necks are often made from plastic, aluminum, or steel. Early versions of the part were little more than a steel pipe gas welded to a piece of steel plate, with a paper gasket to create a seal.

Modern water necks are often machined from solid pieces of aluminum. Grooves are sometimes cut into the water neck’s mating surface, allowing for the use of o-rings instead of paper gaskets. Welds on many aftermarket and factory water necks are performed by robotic welding machinery instead of humans. Robotic welding processes ensure the finished product looks virtually seamless, as though machined from billet.

Why do Water Necks Fail?

  • Water necks do not fail often, but when they do, first check the mating surface and then look for cracks in the housing.
  • It’s more common for the gasket to start leaking than for the housing to become cracked.
  • Vibration may cause the housing to crack over time under normal driving conditions.
  • Age, heat, oxidation, and fluids cause gaskets to fail under normal operating conditions.

What are the Symptoms of Water Neck Failure?

  • A coolant leak is likely to be the first thing you notice if your water neck, or its gasket, fails.
  • Your vehicle’s engine may overheat due to coolant loss.

What are the Implications of Water Neck Failure?

  • Operating an overheating engine for any length of time may damage costly internal parts.
  • Coolant is hazardous to wildlife and pets. Coolant leaks need to be diagnosed and repaired as soon as you notice them.

Occasionally, diagnosing a coolant leak is as easy as popping your hood and tracing it back to a leaky water neck. Repairing the leak may be a simple matter of replacing the water neck or its gasket. Whatever you do, do not continue to drive your car or truck if it starts to overheat. Pull over, call for help, and schedule an appointment at your local Pep Boys once you and your ride are safely off the road.

If you have questions or concerns about water necks or any of your vehicle’s components, come into your local Pep Boys where we can answer any question, help you find any part, or perform any vehicle service you might need.