How to Replace the Thermostat on Oldsmobile Cars

by Contributing Writer; Updated June 12, 2017

If you need to change the thermostat in your Oldsmobile car you will need basic hand tools, a few dollars for replacement thermostat and RTV gasket maker to complete the job. If you've noticed that your engine had been running hot, this could be all it will take to keep your aging Oldsmobile car on the road for years to come. When the thermostat stops working, the engine overheats, and when this happens on an engine that has high miles, it can cause several issues that could cause the need to overhaul the engine.

Under The Hood:

 How to Replace the Thermostat on a 1997 Cutlass

Pesky Petcock

To lift the front, I put the floor jack in the center under the crossmember and then put jack stands under the frame behind the front wheels. To get to the petcock so I could drain the cooling system, I had to remove the lower splash shield. The petcock was next to the condenser-to-radiator bolt and faces forward. It's made of plastic and it was stubborn to open. I sprayed it with some penetrating lubricant to free it up so I didn't I break it trying to get it open.

Burping the System

I torqued the thermostat bolts to 18 foot-pounds. I refilled the cooling system with a 50 percent solution of good-quality ethylene glycol antifreeze and drinking water. I had to remove the bleedscrew on the water outlet housing and then replace it when the coolant started to bubble out. I almost forgot put the bleedscrew back in before I started the engine, which would have sucked air into the system.

 How to Replace the Thermostat on a 3800 Engine

Open the hood for access to the engine compartment. Locate the top radiator hose and trace it to the engine.

Unscrew the hose clamp securing the hose to the thermostat-housing inlet pipe with a slotted screwdriver. Pull the pipe away from the pipe.

Unbolt the screws holding the thermostat cover in place with a socket wrench. Pull the housing cover off by hand. Pull the old thermostat out of the assembly by hand.

Insert the new thermostat with the spring side in first. The thermostat can just be dropped in the housing.

Scrape the gasket material off the mating surfaces of the housing with a razor scraper. Ensure all the black gasket material is removed before applying the new gasket.

Apply the new gasket on the mating surface of the thermostat cover. Ensure the bolts holes match up.

Bolt the cover back on to the housing with a socket wrench. Ensure the bolts are tight to create a seal for the gasket.

Slide the hose back over the inlet pipe. Tighten the hose clamp with a slotted screwdriver.

Twist the radiator cap counterclockwise to pull off the radiator. Fill with pre-mixed coolant until the radiator cannot hold any more.

Start the car and allow it to idle. When the vehicle warms up, the level will drop. Fill with more coolant until the radiator cannot hold any more.

Turn the car off. Tighten the cap back on to the radiator. Close the hood.

Items you will need

  • Slotted screwdriver

  • Socket wrench

  • Socket set

  • 1 gallon pre-mixed antifreeze

 How to Replace the Thermostat in a 2002 Oldsmobile Alero

Proceed directly to Step 4 if your Alero has a manual transmission.

Remove the three bolts securing the heat shield to the exhaust manifold, using a ratchet and socket, and remove the heat shield. Remove the oxygen sensor from the exhaust manifold with a ratchet and oxygen sensor socket. You do not need to disconnect the oxygen sensor, simply set it aside.

Raise the front of the Alero with a floor jack and slide jack stands under its frame rails. Lower the Olds onto he jack stands. Crawl beneath the vehicle and find where the exhaust flex pipe connects to the exhaust manifold. Remove the three flex pipe-retaining nuts from the manifold’s studs using a ratchet and socket. Pull the flex pipe rearward to clear the manifolds studs, then downward to disengage it from the manifold.

Raise the vehicle off the jack stands with the floor jack and remove the jack stands. Lower the Alero to the ground.

Unscrew the cap from the Alero’s coolant overflow tank. Position a drain pan under the petcock on the bottom of the radiator. Turn the petcock counterclockwise until it stops to begin the flow of coolant from the radiator. Once the coolant stops flowing, tighten the petcock. Proceed to Step 7 if your Alero has a manual transmission.

Remove the eight exhaust manifold-to-cylinder head nuts with a ratchet and socket, and pull the exhaust manifold from the engine compartment. Pull the exhaust manifold gasket from the cylinder head and discard it. Clean the mating surface on the cylinder head and manifold with a plastic gasket scraper.

Look on the middle of the engine block on the passenger’s side and find the metal housing bolted to the water pump housing; this is the thermostat housing. Remove the two bolts, securing the thermostat housing.

Push the thermostat housing and hose forward to expose the thermostat below it on an automatic transmission Alero. On Aleros with a manual transmission, pull the thermostat housing and hose upward to expose the thermostat. Pull the thermostat from the water pump housing.

Install the rubber seal around the perimeter of the new thermostat if it’s not pre-installed from the box. Guide the thermostat into the water pump housing with the spring side facing out of the water pump housing.

Reposition the thermostat housing over the top of the thermostat and hand-thread the two thermostat housing bolts. Tighten the two thermostat housing bolts to 2 foot-pounds using a torque wrench and socket. Proceed to Step 17 if the Alero has a manual transmission.

Slide a new exhaust manifold gasket onto the exhaust manifold studs on the cylinder head. Install the exhaust manifold onto its studs on the cylinder head and hand-thread its retaining bolts. Tighten the exhaust manifold bolts to 9 foot-pounds, starting from the top center nut and working outward, using a torque wrench and socket.

Lift the Alero and slide jack stands under the subframe. Lower the Alero onto the jack stands.

Pull the old gasket from the groove inside the flex pipe and set a new gasket into the groove. Guide the flex pipe flange onto the studs on the exhaust manifold and hand-thread the retaining bolts. Tighten the flex pipe bolts to 26 foot-pounds with a torque wrench and socket.

Raise the Alero off the jack stands and remove the jack stands. Lower the vehicle to the ground.

Apply a thin coat of an anti-seize chemical to the threads of the oxygen sensor and hand-thread the sensor into the manifold. Tighten the oxygen sensor with a ratchet and oxygen sensor socket.

Set the exhaust manifold heat shield onto the exhaust manifold and hand-thread its retaining bolts. Tighten the heat shield bolts to 18 foot-pounds with a torque wrench and socket.

Add 50-50 premixed Dex-cool coolant to the overflow tank slowly until the level reaches and stays consistent at a level at the top of the coolant overflow tank’s label. Tighten the coolant overflow tank’s cap.

Start the engine and increase the rpm to between 2,000 and 2,500 until it reaches operating temperature – roughly halfway up the temperature gauge. Allow the engine to idle for three minutes and shut it off.

Allow the engine to cool until it is cool to the touch. Check that the coolant level is still at the top of the coolant overflow tank’s label. Add more 50-50 premixed Dex-cool coolant as needed. The 2.2-liter engine has a total coolant capacity of 2.15 gallons, but the exact amount required to fill it may vary.

Take any old coolant to a nearby automotive fluid disposal center. Some auto parts stores take old fluids free of charge.

Items you will need

  • Ratchet

  • Socket set

  • Oxygen sensor socket

  • Floor jack

  • Jack stands

  • Drain pan

  • Plastic gasket scraper

  • Torque wrench

  • New exhaust manifold gasket

  • New flex pipe-to-exhaust manifold gasket

  • Anti-seize chemical

  • 3 gallons 50-50 premixed Dex-cool coolant

 How to Change a Thermostat on a 1999 Oldsmobile

Remove the radiator hose from the thermostat housing by prying the old retaining clip off of the hose with a screwdriver. Pull the hose off of the thermostat housing.

Remove the bolts that hold the thermostat housing onto the intake manifold of the Oldsmobile with an adjustable wrench. With the bolts removed, lift up on the thermostat housing to remove it from the manifold.

Pull the old thermostat out of the intake manifold and plug the hole with a cotton towel.

Scrape the old gasket off of the intake manifold with a razor or a scraper. Do not get any of the old gasket into the intake manifold.

Remove the cotton towel from the hole in the intake manifold and place the new thermostat into place. The thermostat will be marked to indicate which end should be placed into the intake manifold.

Place a bead of silicone RTV gasket maker onto the bottom edge of the thermostat housing and then bolt the housing back onto the intake manifold of the Oldsmobile.

Place a band clamp onto the radiator hose and secure the radiator hose back onto the thermostat housing.

Items you will need

  • Screwdriver

  • Bucket

  • Wrench

  • Cotton towel

  • Scraper

  • 1999 Oldsmobile thermostat

  • RTV gasket maker

  • Band clamp

 How to Change the Thermostat in a Oldsmobile Alero

Drain the cooling system. Take out the bolts that hold the water pump feed pipe to the thermostat housing.

Lift out the thermostat-housing-to-water-pump feed pipe. Pull out the thermostat.

Set the new thermostat in position. Connect the thermostat housing-to-water-pump feed pipe.

Set the bolt in place that holds the thermostat-housing-to-water-pump feed pipe. Torque the bolt to 89 inch pounds. (See Tips and install the exhaust manifold if necessary.)

Refill the cooling system to the proper level with the appropriate type of coolant. Start the engine and check for leaks. Make the necessary adjustments to coolant levels to assure optimum engine performance.

Items you will need

  • Mechanic's toolset, including a full socket set, wrenches and screwdrivers

  • Replacement thermostat, new or rebuilt

  • New gasket for thermostat

 How to Change the Thermostat on a '99 Intrigue

Take the radiator hose off the thermostat cover by loosening the nut that holds the band clamp around the hose. With the hose loosened, pull the radiator hose off the thermostat cover.

Loosen the cover by removing the bolts that hold it onto the top of the engine with an adjustable wrench. Remove the cover from the engine.

Pull the thermostat out of the engine and discard it. Scrape the old paper gasket off the engine with a small scraper. To prevent getting any gasket into the engine, plug the hole that the thermostat was in with a shop towel. Once the gasket has been scraped off the engine, remove the shop towel from the hole.

Place a new thermostat into the engine with the correct side up. (The thermostat will be stamped with the word "up" or "top"--this end should stick out of the engine.)

Place RTV silicone gasket maker onto the mating surface of the engine. (Due to the Intrigue's age, the use of RTV silicone gasket maker is preferred over a paper gasket to prevent leaks due to imperfections in the mating surfaces of the engine and the thermostat cover.)

Bolt the cover back into place using the original bolts that were removed. (The RTV silicone gasket maker will squeeze out; this is normal.) Place the radiator hose back onto the cover and tighten it into place.

Items you will need

  • 1999 Intrigue thermostat

  • RTV silicone gasket maker

  • Nut driver

  • Adjustable wrench

  • Plastic scraper

  • Shop towels

About the Author

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