How to Replace the Exhaust Maniverter and rear converter for the 09-11 Ecotec engine

This is going to be a comprehensive guide on how to replace the Exhaust Maniverter and the Rear Catalytic Converter on a 2009-2011 Aveo (the car I will be referencing is a 2010) for those who live in the Salt Belt, and coastal areas, PB Blaster or Liquid Wrench will be your VERY BEST Friend here, since the bolts holding the Maniverter to the flex pipe, as well as the bolts holding the rear converter to the flex pipe and the rest of the exhaust system are exposed to the elements (i.e ROAD SALT). and I would recommend replacing BOTH the Maniverter and the Rear Converter as a set, because if you are replacing one, the other will likely be in the same condition. (I.E if the Maniverter is thermally damaged, or is poisoned from coolant getting into the exhaust from a blown head gasket)

TOOLS YOU WILL NEED:

a 1/4" Ratchet (the space you have to work in is EXTREMELY tight up top)
a 10mm 1/4" drive socket (for the lower heat shield bolts, and the manifold to cylinder head nuts)
a 12mm 1/4" drive socket (for the Upper heat shield bolts, as well as other bolts in the same area)
a 3/8" Ratchet
an E12 External Torx socket (for some hidden bolts)
a 1/2" Ratchet
a 1/2" breaker bar (an impact wrench WILL NOT fit in the space between the flex pipe and the front subframe)
a 14mm 1/2" drive socket
a Catch pan
a Floor Jack
2 Jack Stands (Safety First!)
a 10mm wrench (a Ratcheting Wrench is HIGHLY Recommended)
an Oxygen Sensor Socket
a small straight pick
a Quart of your Preferred Engine oil


REPLACING THE MANIVERTER

Step 1: Remove the Negative Terminal on the battery. (this prevents damage to the ECM, as well as erases the DTCs)

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Step 2: raise the front of your Aveo using the Floor Jack, and set your Jack Stands on the Front Subframe, making sure they will not interfere with you removing the Rear Converter, but to where they will hold the car effectively. (we don't want any squished Aveo Owners!)

Step 3: remove the Power Steering Pump Stiffening bracket and lifting eyelet from the Right side of the Cylinder Head (a 12mm bolt on the PS pump, and a 12mm nut on the head for the stiffening brace, and a 12mm stud for the lifting eyelet. these need to be removed, or else good luck getting the heat shield out)

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Step 4: remove the Dipstick and Dipstick Tube from the Oil Pan; make sure to have your catch pan ready, or else you WILL have a mess in your driveway like I did.

Step 5: disconnect the Upstream Oxygen Sensor from the engine harness, and then unclip the connector from the holding bracket

Step 6: using an Oxygen Sensor Socket (a 7/8" socket or Crows Foot with a slot cut in it) remove the Upstream Oxygen Sensor from the Maniverter (Put it in a SAFE Place, as these suckers are $238 a pop! and when you go to reinsert it in the New Maniverter, be sure to put Sensor Safe Anti Seize compound on the threads on the sensor. OPTIONAL: you can remove the Downstream sensor from the Flex pipe in the same manner as well, to prevent damage to the sensor when replacing the rear converter)

Step 7: remove the Lifting Eyelet/Upstream Oxygen Sensor connector Bracket from the left side of the cylinder head.

Step 8: remove the 12mm bolts securing the top part of the Maniverter Heat Shield to the Cylinder Head

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Left Side
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Right Side

Step 9: remove the 2 10mm bolts securing the lower part of the heat shield to the Maniverter (as mentioned in the Tool List, a Ratcheting Wrench is HIGHLY Recommended! Note to Salt Belt and Coastal Owners: exposure to Road Salt and Coastal Spray will likely cause these bolts to snap off; Make sure the Maniverter you buy comes with replacement bolts!)

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Left Side

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Right Side

Step 10: lift the heat shield carefully out of the engine compartment

Step 11: remove the 2 E12 bolts that secure the Maniverter to the Engine block. (Note to Salt Belt and Coastal Owners: these bolts will likely snap off due to exposure from Road Salt and Coastal Spray; make sure the Maniverter you get comes with replacement bolts!)

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Location of the E12 bolts, as they sit on the Maniverter

Step 12: remove the 9 10mm nuts that secure the Maniverter to the Cylinder Head; starting from the middle of the head, and working your way out.

Step 13: remove the 3 14mm nuts that secure the Maniverter to the Flex Pipe (Note to Salt Belt and Coastal Owners: these nuts are likely smaller in size due to exposure to Road Salt and Coastal Spray; be VERY Careful when attempting to remove these nuts, or they WILL Round off, and then you will have to resort to cutting the studs off; make sure your new Maniverter comes with new studs and nuts!)

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Step 14: lift the Maniverter out of the engine compartment; then remove the old manifold gasket from the cylinder head

Step 15: using your small pick, remove the Donut gasket from the Flex Pipe (check and make sure your new Maniverter comes with all gaskets!)

Step 16: Clean the Cylinder head around the exhaust ports of any soot, old gasket, or corrosion; and do the same to the Flex Pipe flange (a Clean mating surface means it will be leak free! use a piece of Brown Scotch Brite pad or 1" angle grinder disc on the flex pipe, and something NON MARRING on the cylinder head; preferably a Scotch Brite Roloc bristle disc on a 1" angle grinder)

Step 17: Installation is Reverse of Removal.

Step 18: top up the engine oil that was lost when the Dipstick Tube was removed from the Oil pan.


REPLACING THE REAR CONVERTER

Step 1: remove the 4 14mm Nuts that secure the Rear Converter to the Flex pipe and the Cat Back part of the Exhaust System (NOTE: an Impact wrench WILL NOT fit in the space underneath, or else YOU WILL Round off the nuts, and have to resort to cutting them off)

Step 2: if you are not replacing the Maniverter, remove the 3 14mm nuts that secure the Flex Pipe to the Maniverter.

Step 3: Disconnect the Downstream Oxygen sensor from the Vehicle Harness (this will prevent pulling the wiring out of the sensor and having to run to the parts store for a new one at $200 a pop! OPTIONAL: you can completely remove the sensor from the flex pipe if you do not want to risk damaging the sensor; just make sure to put Sensor Safe anti Seize compound on the threads of the sensor before you reinstall it)

Step 4: push the Flex Pipe towards the front of the car, to both disengage the gaskets from the converter (more than likely, these gaskets will come off in sharp pieces, so BE CAREFUL!) and to clear the studs on the front of the converter.

Step 5: remove the converter from the Cat Back part of the Exhaust system.

Step 6: clean any gasket remains, and any corrosion from the two flanges (a Clean Mating Surface will mean the joints will be LEAK FREE!)

Step 7: Installation is reverse of Removal (but MAKE SURE you put the converter where the long side of exhaust pipe faces the front of the car, or else the converter will not fall under the heat shield attached to the underbody, and it will not flow correctly. And if the converter does not come with bolts, make sure you get them before you begin, or else you will not be able to attach the converter to the flex pipe and cat Back part of the system)

FINAL RECOMMENDATIONS

make sure you fill out any warranty forms, as well as verify that the Oxygen Sensor Voltages are acting normal (Upstream sensor changes Voltages rapidly, while the Downstream sensor changes much more slowly; if not, you might want to check the health of your sensors) hope this how to Guide helps!

Thanks for posting this! My father's 2011 Aveo5 had it's catalytic converter collapse on itself recently and I was just about to do this project myself as well.