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2008 chevy trailblazer_ls
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OK so I am two timer at this. First manifold cracked at 81,000 miles and now at 120,000 it is cracked again.
That stinks.
Last Friday when mine was repaired I asked the service writer if this is going to happen again, he said no the new manifolds are not the same as the cracking ones, he new ones are manufactured differently to prevent this? Did I take the carrot?
 

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Keith, Was your replacement manifold from GM?
 

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2009 saab 9_7x
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Keith, Was your replacement manifold from GM?
The first one was replaced at the Chevrolet dealer but I cannot be positive they used a true GM part or something else. It was replaced back in 2008 so I guess it would not hurt to call the dealer.

I may have a little different outlook on this. I bought this vehicle new and it has been one of the most reliable cars I have owned. I am frustrated that it cracked again but not overly bothered by it.

My Trailblazer is used mostly by my wife but it also used for a lot of long distance vacations as well as I tow a 5,000lb trailer. If there is a header available I would prefer that anyway as it would help boost low speed torque for when I tow.
 

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2008 gmc envoy_sle
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That stinks.
Last Friday when mine was repaired I asked the service writer if this is going to happen again, he said no the new manifolds are not the same as the cracking ones, he new ones are manufactured differently to prevent this? Did I take the carrot?
I wonder if someone could simply compare part numbers? This is interesting...
 

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2008 gmc envoy_sle
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That stinks.
Last Friday when mine was repaired I asked the service writer if this is going to happen again, he said no the new manifolds are not the same as the cracking ones, he new ones are manufactured differently to prevent this? Did I take the carrot?
I wonder if someone could simply compare part numbers? This is interesting...
So is the consensus that the service writer was blowing smoke up you arse? I noticed that no one has commented on this potential nugget of information...
 

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2009 saab 9_7x
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This weekend I plan to replace the thermostat, belts, hoses, coolant temp sensor and install my new Gibson cat back exhaust. I will putt the heat shield off the manifold and get the part number. At least I can see if it was a genuine GM part or a clone.
 

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2008 chevy trailblazer_ls
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This weekend I plan to replace the thermostat, belts, hoses, coolant temp sensor and install my new Gibson cat back exhaust. I will putt the heat shield off the manifold and get the part number. At least I can see if it was a genuine GM part or a clone.
Alright!
 

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2008 gmc envoy_sle
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That stinks.
Last Friday when mine was repaired I asked the service writer if this is going to happen again, he said no the new manifolds are not the same as the cracking ones, he new ones are manufactured differently to prevent this? Did I take the carrot?
Jbones, do you have the part number of the manifold the dealership installed for you? Please let me know, thanks.
 

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2008 gmc envoy_sle
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It says 12637060 (MANIFOLD).
Thanks for checking for me jbones, I appreciate the super fast response.
Here is the email I sent to GMPartsDirect

"I am looking to purchase the part identified in the subject line
above. I heard a rumor that GMC recently changed the exhaust manifold
because the old manifolds were prone to cracking and the new manifold
is "beefier". Can you confirm that you stock the brand new updated
manifold/part number or not? Thanks."

Here is their response:
"Thank you for your emailed inquiry to us at www.GmPartsDirect.com. We look forward to receiving your order. I have entered your supplied information into our licensed GM parts catalog and below are the part numbers requested and are verified as being correct per the VIN supplied.
12637060 Exhaust Manifold (includes studs)".

So, they did not answer my question but the part number they supplied certainly matches yours. Either GMpartsdirect carries the new manifold or there is no such thing as a new manifold, impossible at this point to tell. My detective work is not quite panning out just yet :duh:
 

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2008 gmc envoy_sle
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Found this archived post, interesting:

http://forums.trailvoy.com/archive/index.php/t-30899.html

ontimeman 11-28-2007, 11:34 AM
Hi,, i am a new member, am also a chevy partsman,,, for info... exman part #88890560, this would be for a 2002 thru 2005 4.2, ... list is approx 207.33, depends on dealers matrix pricing though,, a bussiness should expect to pay around 155.50.... 2006 and up use #12587310.. list is approx 226.74 and shop cost approx 155.50. dont know what if anything is the differance besides the price as we have'nt sold one in a longgggg time to see them for comparrison. :D
 

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gmc
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Cracking

From all the pictures on here the manifolds all tend to crack in the same area.

The problem is the manifold thermal expansion, when they experience thermal shock they crack especially in the common down spout.

One permanent fix is the proposed dual outlet manifold, the design will eliminate the high stress area. It needs 8 more people to come forward with $$ to get the design moving.

http://forums.trailvoy.com/showthread.php?p=1144045#post1144045

Its not going to happen for free.
 

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2009 saab 9_7x
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I installed the Gibson cat back exhaust yesterday. Thankfully the noise was not from another cracked manifold. The front part of the muffler was rotted away.

I knew the resonator was shot as it was vibrating and rattling inside but I did not suspect the muffler was as bad as it was. So I escaped a second manifold, plus I love the sound of the Gibson!
 

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2008 gmc envoy_sle
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From all the pictures on here the manifolds all tend to crack in the same area.

The problem is the manifold thermal expansion, when they experience thermal shock they crack especially in the common down spout.

One permanent fix is the proposed dual outlet manifold, the design will eliminate the high stress area. It needs 8 more people to come forward with $$ to get the design moving.

http://forums.trailvoy.com/showthread.php?p=1144045#post1144045

Its not going to happen for free.
If the cracks are a result of thermal shock, then wouldn't a process like ceramic coating fix this problem?
 
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