Where Is the Thermostat on a 2004 Alero?


In 2004, after more than a century, Ransom E. Olds' namesake company closed its doors. But before doing so, Oldsmobile turned out two last Aleros. The very last car, a V-6 GLS, is still on display in a museum in Lansing, Michigan; the second-to-last car, a four-cylinder GL1, somehow found its way down to Florida. There, about a decade later, it wound up on a lift in a little garage, waiting for a new thermostat.

Thermostat Replacement

  • While I generally try not to be critical of pieces of history, it must be said: this engine was not the best-designed where thermostat housings were concerned. The thermostat housing on this engine is inexplicably tucked up under the exhaust manifold, so close to it that you have to take the manifold off to get to it. I started by draining the coolant.

    The good news is that the exhaust manifold on the 2.2-liter is pretty easy to take off, as manifolds go. I started by removing the manifold's heat shield, which was held to it with a vertical stud going down into the manifold, and two more going horizontally into the block. I then unplugged the oxygen sensor, and removed it. If this car had had a block heater, that would have been next. I removed the nuts on the 10 manifold studs, and slid the manifold backward off the studs. There was enough wiggle room in the exhaust system to get the manifold off the engine, but I'd have unbolted the system from the manifold and pulled that off first if it hadn't wanted to move.

    With the manifold off, I threaded two nuts onto one stud, and used a wrench to turn the rear one counterclockwise, locking it against the front nut. After applying some pressure to the rear nut, the stud began backing out of the head. I removed it, and then the rest of the studs, and tossed them and the nuts in the trash. These studs and nuts are known as "torque to yield" fasteners, meaning that they permanently stretch after being tightened. You can't reuse a TTY fastener -- new ones are the only option. After getting the studs off, I pulled the old exhaust gasket off, and cleaned the mating surfaces on the engine and manifold with a gasket scraper.

    After all that, the thermostat itself was easy; two bolts at the pipe junction, pull the pipe forward and off the engine, and then pull the thermostat out. I cleaned the mating surface, installed a new thermostat in the same orientation as the old one, and reinstalled the pipe. Its bolts took 89 inch-pounds of torque. At this point, I went ahead and refilled the cooling system; better to find out about a major leak now than after the manifold is back on.

    I installed new studs using the two-nut process, and tightened them to 89 inch-pounds. I used a wrench to hold the rear nut while I pulled the front one off, to keep from backing the stud out of the hole. With all new studs installed, I slid a new gasket on and slid the manifold over the studs. I installed the new nuts, and tightened them to 124 inch-pounds. The tightening sequence started at the top nut in the middle; I proceeded to work in a crisscross pattern from the middle, working my way back and forth to the outermost bolts. I installed the O2 sensor, and tightened it to 22 foot-pounds. The block heater would have gotten the same 22 foot-pounds, if this car had had one. Finally, the heat shield went on, and I tightened its fasteners to 17 foot-pounds.

    After bleeding the cooling system and topping it up, I checked for leaks and turned the car loose. One more little-known piece of history, back on the road again.

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