: Removing exhaust down pipe on 99 Seville

06-12-11, 02:59 PM
I have finally started on this, and it says to remove back downpipe on it. I was able to seperate it from the exhaust system behind it, but to remove it from the manifold is quite another story. I can't get one of the bolts broke
loose for the life of me. Is it really needed to take it off? I can't see what it would impeed when dropping the cradle.
I also can't find the connections for the electrical harness underhood relay center, is this the computer connections that are refered to in other threads, under the dash? Just says "Disconnect the electrical harness from the underhood relay center"
BTW, I have a 97 Seville Factory Service Manual, and this is a 99 Seville. I didn't think that would make a difference, maybe it does?

Also, nowhere in the removal instructions did it mention disconnecting from the heater core, I know it is needed, just seemed weird that it wasn't listed that I found.
Thanks for any help

06-12-11, 04:43 PM
I have left the down pipe connected until the cradle is out of the car. It is much easier to get some leverage on those bolts that way. Just disconnect the 4 catalytic conv nuts and disconnect the wiring harness to the rear O2 sensor.

As for the electrical, there should be a fuse box on the passenger side. You have to get it apart and flip it over. There are 3 8mm bolts that hold 3 large square connnectors under there. 2 stay with the body and 1 comes out with the engine. There is also a large connector on the driver strut tower that needs disconnecting.

For the heater hoses, the connections are on the drivers side above the trans. Two rubber hoses come out at the firewall. They connect to two steel pipes in that area.

You should really get a service manual for your 99. There are some major and minor differences between those model years.

06-12-11, 05:03 PM
Thanks for the reply. I already disconnected the hoses, I just found it odd that it wasn't mentioned anywere that I saw, and I am learly of what else wasn't mentioned.
Just to be sure, the rear O2 sensor you are reffering to is the one behind the cat converter right? I didn't see one on the back side exhaust maniford, just the one on the
front, and the one behind the cat converter.
Thanks alot

06-12-11, 05:43 PM
Yes, the O2 sensor after the cat. The wiring is behind a heat shield that may be riveted in place. Just drill the rivets with a 1/4 inch bit. There is an O2 sensor on the rear manifold. You will see it when you drop the cradle. Watch out for the strut and control arm sensor wiring. On my 2000, the connectors are up on the inside of the body and are a bit of a pain to disconnect. Watch out for the rear brake lines as well. They may run along the cradle and will make dropping it out difficult until you remove them.