How do you change a thermostat on a 3.4l v6 engine in a lumina?

Answer 1

Answer: With moderate difficulty. Typical of automotive engineers, they designed a 3/4 inch tube to block the removal of the upper radiator hose connection to the thermostat. Instead of using a simple bolt and spacer, they have a one piece bolt and stud holding the upper radiator hose connection and a brace for the 3/4 inch tube. The tube can only be properly removed if the exhaust manifold is removed, as the exhaust manifold was installed over the attachment point of the tube. Not real bright on the engineer's part. The easy way to replace the thermostat is to remove the nut holding the 3/4" tube from the flange stud. Next remove the bolt/stud holding the bottom of the thermostat flange. You may have to grind a cheap 13mm open end wrench thinner to fit the tight space. I used a cheap stubby 13mm open end ground thin. In the process of removing that bolt/stud, the small attachment bracket for the 3/4" tube will be bent. No problem...just bend it straight later. Remove the other bolt holding the flange covering the thermostat. Clean the old rubber gasket from the counter bored thermostat seat. The thermostat comes with a rubber gasket, and also a paper gasket for spacing. If you don't use the paper gasket, the flange will be bent when you tighten down on the bolts because the rubber gasket is thick. Instead of reusing the original lower bolt/stud combination, I used an 8mm-1.25 X 45mm bolt, nut, a flat washers, and a spring type split lock washer . Position the thermostat with the rubber and paper gasket, the upper radiator piping flange over the thermostat, and install the upper bolt finger tight. Straighten the previously bent attachment flange on the 3/4" tube. Put the lock washer and the flat washers onto the bolt. Now holding the 8mm nut between the thermostat flange and the flange for the 3/4" tube, screw the 8mm bolt through the tubing flange and the nut you're holding and into the flange for the thermostat. It may take two wrenches: One to hold the nut, and the other to turn the bolt. You will simply have to tighten the bold in such a manner that the nut and the bolt tighten down simutaneously to where the thermostat flange and the 3/4" tubing flange are tightened snug. It is more important that the nut holding the thermostat flange is tight than the bolt holding the 3/4" tubing flange. The 3/4" tubing only has to be secure in that it won't have any looseness. Note: Do not use a bolt any longer than the 45mm length. If you do, you'll probably crack the thermostat mount or punch through and hit coolant. This explanation sounds difficult to understand, but once you get into it, it will all make sense. You can use two or three flat washers to make sure that you don't go too deep with the bolt.