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Author Topic: 3.4L V6 Teardown Part 5 - Rear Exhaust Manifold  (Read 11448 times)
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Wolfy1969
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« on: January 05, 2011, 03:02:33 PM »

I know...I said heads were next...well, they are, but you have to get the exhaust manifolds off first because they're bolted to the head.

Straight up - right off the bat....this sucks.  Period.  There's no way around it.  Of course, ideally if I had the engine out and mounted on a stand, this would be a piece of cake.  But I don't, so doing this with the engine still in the car is a major pain, but it CAN be done...

Exhaust sucks because of not only where the parts are that have to be removed and for the back at least, you'll be working blind and from feel alone, but the nature of the extreme heat, moisture and contraction all work to corrode the pipes, fittings and the fasteners that hold it all together.  Bolts are often very hard to remove, and the chance of rounding a bolt head or nut off, or even snapping a bolt or stud is fairly high.  I couldn't even take a lot of pictures to help because I couldn't see what I was doing myself.  The first time we took this apart, we found 3 studs on the front manifold that had broken off in the head.  This was causing a vacuum and exhaust leak because the manifold was no longer being held tightly to the head.  I had to have a machine shop drill out those studs and re-tap the holes for me.  I put all new studs and nuts on, so again, mine will go easier this time, but it's still a bear, and mine were no fun at all the first time around.  Some penetrating oil/spray may be of use here to loosen really stuck bolts as well as leverage pipes on ratchet handles.  Just go slowly and rock it a little at a time to break it free instead of throwing all your muscle at it at once - that's more likely to snap something off or round off a bolt head.

The easiest way to start tackling this is to start with the crossover pipe that connects the two manifolds.  All the manifolds have a 2 piece heat shield on them held on with small 10mm bolts.  For the crossover pipe, you only really need to get the top shield off to get at the bolts to disconnect it.  Here's the one at the back:



The front one used to go here under the right front engine mounting bracket.  Mine was stripped though, so I twisted some bailing wire around the shield near the front just to stop it from rattling around with vibration:



With the shield off, you can now see the crossover pipe which takes the exhaust from the front head, joins it with the back one with some of it going up the EGR tube, and sends it out the exhaust pipe.



There is a flange like this at both ends of the crossover pipe.  There are actually 3 bolt/nuts in a triangle configuration - 3rd one is behind the pipe.  These really suck - they are often among the most rusted and most stubborn parts to remove on an engine.  Soak them in penetrating spray, let them sit a while, put a ratchet on them, try to move them a bit..if they won't maybe tap the ratchet handle with the side of a hammer to break them free, but don't wail on it - you might snap it off...



Front Flange:



You can go ahead and completely remove the crossover pipe now depending on what it is you're repairing.  For now, I was aiming to get that back head out since that's my trouble spot, so I just broke the back connection for now.

Next, remove the bolts for the rear manifold shields.  There's 2 10mm bolts at about the highest point on the shields - you'll have to feel for them, and/or look ahead at the pics of the shields out so you can see where the holes are.



Once the bolts are out, you can slide the top shield off.  You'll see it has a cutout where it sits on the exhaust pipe, and a hole where the EGR tube slides through.  Slide it up and over the EGR tube and take it out.



Looking at the back end with the shields gone.  That thing sticking up smack in the middle of the picture with the wire harness coming out of it?  That's one of two O2 sensors.  The other one is under the Tek by the Catalytic Converter.  To the right is the EGR tube, immediately to its left is the right hand stud that the ignition module sits on.  The left one came out when I took the bolt off.



Next, slide the bottom shield out.  This isn't much fun - I found it easiest to slide it out to the left where the alternator was.  It takes some wiggling and positioning to get it out, but it will come out.



Now, find the top 3 13mm manifold bolts.  My socket in this pic is on the 2nd one.  You can find these by feel.  Note that when you find the 3 top ones, the 3 bottoms ones are directly below them.



The bottom ones suck...plain and simple...the hardest one by far was the last one on the bottom right.  Maybe if I had gone ahead and taken the crossover pipe completely out it might've been easier to get back there, but that one was about the hardest thing I've done so far in this whole teardown...I still feel it today.  Ever seen that funny pic where the guy is laying on his engine and it looks like the Tek is eating him like a shark?  That's what you'll be doing here and probably what he was doing...lay some blankets or something over the front end to cushion your gut and get in there...

I think it would be easier if I could get to them, from underneath if necessary to unbolt just the 2 bolts that bolt the back manifold to the exhaust pipe collar, and then take the head and manifold out as one unit and then separate them.  If you can do it this way, more power to you!





« Last Edit: January 05, 2011, 03:40:35 PM by Aztek-Knight » Logged
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