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2006 gmc envoy_denali_xl
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Discussion Starter #1 (Edited)
Hi All,

New to this site...lots of great info here. I did some searching, but can't find an answer to my question.

I bought an '06 GMC Envoy XL and only drove it 100 miles before the check engine light came on with a misfire on cylinder 6. Diagnosed it as a bad lifter (AFM) and observed the lifter not moving with the valve cover removed.

I'm doing all of this with the engine still in the truck.

I have a Haynes manual and it says to remove the cylinder head, I have to unbolt the exhaust manifold from the head. It does not say I have to remove it. I have it unbolted, but I don't see how I can get to the bottom cylinder bolts to remove it.

Anyone done this job and can give me some guidance? I tried to bite the bullet and remove the exhaust manifold, but the 3 nuts going to the pipe won't come off. My impact is not strong enough and I can't really get at one of them.

This is the last step holding me back! Please help!
Thanks!
 

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2006 gmc trailblazer_ls
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39 Posts
If you have it off the head just pull it out of the way. I pulled the head and then motor on mine without taking the manifold off of the pipe.


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2006 gmc trailblazer_ls
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If you’re not familiar with the cam/timing on this engine do your research because it is quite a job to do it. You have to pull the oil pan to time it. To pull the oil pan you have to remove front axle shafts and front differential from the oil pan if it is 4x4. If not then it is much easier.


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2006 gmc envoy_denali_xl
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Discussion Starter #4
If you have it off the head just pull it out of the way. I pulled the head and then motor on mine without taking the manifold off of the pipe.


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Thanks! Am I missing some kind of trick to access the cylinder head bolts that are near the exhaust manifold? The manifold pulls away about an inch, but I can't figure out how to get at the cylinder bolts with it still there. How did you do it?
 

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2006 gmc trailblazer_ls
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Thanks! Am I missing some kind of trick to access the cylinder head bolts that are near the exhaust manifold? The manifold pulls away about an inch, but I can't figure out how to get at the cylinder bolts with it still there. How did you do it?


I don’t remember. It’s been too long. I don’t remember there being any bolt by the exhaust manifold. I thought they were all under the valve cover. Also those bolts are known for breaking. I broke all but two on mine. Use an impact on all them that you can to remove them.


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2006 gmc trailblazer_ls
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Crap. I just realized you have a 5.3. All of this crap I’m spouting is for the 4.2 I6. Im pretty sure you will have to remove the manifold completely. Use a map gas torch on those nuts that you can’t get loose. Get them red hot and then hit them with an impact I’m not much help as I’m not familiar with the v8 in the envoy.


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2006 gmc envoy_denali_xl
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Discussion Starter #7
Well, apparently it is required to remove the exhaust manifold and it is a bear! The bolts going into the engine were near impossible to get to, but I managed and didn't break any bolts. The 3 nuts on the manifold to cat flange were another matter. I spend hours trying to get them off, even buying a bigger impact gun, but nothing worked. I ended up using a variety of tools to finally cut the nuts. That freed one, but the other two required me to cut the stud off as well.

Now I am going to work on removing the cylinder head bolts and pray they come out without any issues!
 

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2007 chevy trailblazer_lt
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Well, apparently it is required to remove the exhaust manifold and it is a bear! The bolts going into the engine were near impossible to get to, but I managed and didn't break any bolts. The 3 nuts on the manifold to cat flange were another matter. I spend hours trying to get them off, even buying a bigger impact gun, but nothing worked. I ended up using a variety of tools to finally cut the nuts. That freed one, but the other two required me to cut the stud off as well.

Now I am going to work on removing the cylinder head bolts and pray they come out without any issues!
Did u get through with this. I just did my HG replacement and didn't have problem. I did completely remove the exhaust manifolds tho.

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2006 gmc envoy_denali_xl
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Discussion Starter #9
Yes I finally got the job done. The rest of the job went without a hitch. After I was done, I had to redo some coolant connections due to leaks. So far, so good. Oil pressure has been good and the lifters are no longer making noise.
 

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I recently removed/reinstalled the driver's side cylinder head on my 2006 5.3 without removing the manifold from the exhaust pipe (to fix a collapsed AFM lifter on cylinder 7), but it was a pain. I ran some of those ratcheting-type tiedown straps around the manifold, through the driver's side wheel well, over the tire, and looped the other end around part of the wheel, and was able to pull the manifold far enough from the head to get to the head bolts and get the head out and back in.

It is *much* easier to just remove the manifold, if you can manage to disconnect it from the pipe, but mine would have required a torch (impact wrench wouldn't budge them, just started to deform the bolthead) so I just did it without removing the manifold. I can't vouch for the passenger's side cylinder head, though.
 
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