How to Install a Mazda Protege Car Thermostat

by Jody L. Campbell

If the heater is not working well or at all in your Mazda Protege, the culprit could very well be the thermostat. In today's economy, you could save some serious money on expensive labor costs charged by local repair stations and remove and replace the thermostat yourself. If you haven't flushed your coolant system, or drained and filled, it in a couple of years, it would be a good time to kill two birds with one stone.

Park the Protege on a flat, paved surface, apply the parking brake and release the hood latch.

Place a wheel chock behind one of the rear wheels, then open the hood.

Lift the left front quarter panel of the Protege with the floor jack and place a jack stand under the front left frame rail. Repeat this for the right side to elevate the front axle of the Protege.

If the car is cool, remove the radiator cap. Do not remove the radiator cap if the engine is hot or still warm. Allow ample time for the motor to cool down, and then remove the cap slowly.

Put on safety glasses and crawl under the Protege. Locate the lower radiator hose, and loosen the clamp. Original clamps my be the type where you need to squeeze to tabs together to remove them, or they may be the kind that tighten and loosen with a screw. Use the channel locks for the tab kind or a screwdriver for the screw kind.

Line up the drain bucket beneath the lower radiator hose and remove the hose. Be careful, because the antifreeze will come out quickly. Wipe up any spills immediately with the shop rags.

Replace the lower radiator hose and resecure the clamp. Lower the Protege back to the ground.

Remove the air cleaner assembly in the engine compartment if necessary to access the thermostat. Remove the lid first, then the filter, then the bolts at the bottom of the air cleaner box using the ratchet, socket and the extension.

Disconnect the coolant temperature switch from the thermostat housing.

Remove the upper radiator hose from the thermostat housing. Remove the mounting nuts, the thermostat housing, the thermostat and the gasket.

Thoroughly clean the surfaces of the thermostat housing and the cylinder head housing with the gasket scraper. Take your time and get the two surfaces very clean.

Insert the new thermostat into the cylinder head, making sure the pin is on top and the spring of the thermostat is in the cylinder head side. Install the new gasket so the print side of the gasket is against the cylinder head flange.

Replace the thermostat housing and nuts, and tighten them securely. Do not overtighten, or you could damage the cylinder head.

Replace the upper radiator hose and clamp. Replace the coolant temperature switch, and replace the air cleaner assembly.

Make sure the drain bucket is beneath the radiator neck in the event antifreeze purges air bubbles from the system. Add new 50 percent mixed antifreeze and 50 percent water to the radiator. Add it slowly, using a funnel if necessary. When the radiator is full, start the engine with the radiator cap still off, and allow the Protege to reach operating temperature. Add antifreeze to the radiator as necessary. Fill the surge tank when through. Remove the wheel chock, release the parking brake and test drive. Recheck the antifreeze level a couple times and add as necessary.


  • check Poor the old antifreeze from the drain bucket into the empty antifreeze containers, and discard appropriately.


  • close Clean any antifreeze spills up immediately. Antifreeze has both a sweet smell and taste which can attract pets or small children, and it is highly toxic.

Items you will need

About the Author

Jody L. Campbell spent over 15 years as both a manager and an under-car specialist in the automotive repair industry. Prior to that, he managed two different restaurants for over 15 years. Campbell began his professional writing career in 2004 with the publication of his first book.

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