Hello all,


I have a 2000 Monte with the 3.8L. It has an exhaust manifold leak somewhere in the rear manifold. How hard is this to change out? Cant find any videos on the web. There is no friggin room between the motor and firewall to get to the bolts! I'm an adequate do it your selfer but damn this one looks like a b!+<#!! Should I rock the motor forward or is it possible to rotate the motor down for access? Anyone else out there ever replace the rear exhaust manifold? Any opinions or advice would be appreciated!!

 

Yea, you can get to it by rocking the engine forward. Unhook the dogbones first and hold it forward with a strap or something.. I used a mirror to find the bolts..

 

Thanks for the info! The flex pipe should allow that movement of the motor yeah? I still have no idea if it's coming from the manifold at the head, the gasket, or the flex pipe itself. Is there a gasket between the manifold and flex pipe as well? If so I'll go ahead and change both. But I definitely want to pull the manifold out and inspect it and go from there. Thanks again for your time brotha!

 

Yes, there is a gasket at the head and where the downpipe bolts up. Between the flex pipe and the rubber hangers, the exhaust can move a ton, you should be able to rock the engine forward far enough to easily get your hands back there.

Also, unlike the front cast manifold, the rear is a bunch of welded pipes. It's not common to have a weld crack / leak form but it wouldn't be the first I've seen either. Definitely should be able to tell pretty easily if there is a real sooty area on or near a weld.

 

Thanks again for the info guys. I will dig into this soon. But for now it is team jackstands for this girl. I'm also curious. Has an exhaust leak ever made your car hesitate or act like it's missing on a cylinder? It's probably another issue but I thought I'd ask.

 

Do you know if the leak is head to manifold? Manifold to downpipe? Manifold to EGR? Manifold to Cross over pipe? Or a damaged manifold?
Each one presents it's own issues. Two weeks ago, I resolved an issue with a loose connection between the rear manifold and the down pipe. I did it all from under the car. Since my car does not see any winter weather and I spent a couple days hitting the hardware with PB Blaster, it all came apart pretty easy. New gasket, replace some hardware and all good.
I found my leak because I suspected it (sounds louder than it should have). While under it for other reasons, found I could rock the downpipe at the rear manifold connection, just a little.

 

I am just guessing it is from the head to manifold considering where the noise and exhaust smoke is coming from on a cold start. But yeah it is loud as hell. Has to be the gasket or a cracked weld somewhere like mentioned before . I got underneath the car with it running to check the down pipe and it seems to be okay. But who knows. I'm just gonna spend the extra few bucks and get that gasket for the down tube/flex pipe while its apart.

 

Make sure you either remove the spark plugs or be very careful when removing the manifold.

 

It's certainly a possibility depending how bad the leak is. Any kind of opening to atmosphere ahead of the upstream O2 sensor can cause it to skew fueling as a result.

 

That makes perfect sense. Considering the 02 censor is probably all out of whack due to the exhaust leak. It was running pretty damn good before this. It did have a cylinder misfire (stored in codes) in one of the cylinders back there. But didnt have an issue like now with the uneven idle and throttle hesitation. But the noise I'm hearing from the manifold screams big leak! Gonna change plugs n wires while I have access as well. Any other component that you guys can think of that I should disconnect before rocking the motor forward? Thanks again guys!