Cracked Exhaust Manifold

lmcree

Original poster
Member
Mar 22, 2013
14
My exhaust manifold cracked on my '08 Envoy (I-6). any suggestions on a performance aftermarket manifold? Thanks for the help.
 

Wooluf1952

Member
Nov 20, 2011
2,663
Milwaukee, Wisconsin
http://gmtnation.com/f43/kooks-4-2l-i6-header-5341/

tiphat.gif
Welcome
tiphat.gif


In case you haven't heard:
http://gmtnation.com/f5/welcome-gmtnation-com-heres-story-226/
 

CaptainXL

Member
Dec 4, 2011
2,445
lmcree said:
My exhaust manifold cracked on my '08 Envoy (I-6). any suggestions on a performance aftermarket manifold? Thanks for the help.

On the retail market? Not that I am aware of. Someone was going to make some headers but there wasn't enough interest. But in case you are interested there is a warranty for replacing the exhaust manifold as show below. You need to be within 120,000 miles.




#11150: Special Coverage Adjustment-Exhaust Manifold Warranty Extension - (Jul 25, 2011)


Subject: 11150 - Special Coverage Adjustment - Exhaust Manifold Warranty Extension


Models: 2008-2009 Chevrolet TrailBlazer

2008-2009 GMC Envoy

Equipped with 4.2L Engine (LL8)




--------------------------------------------------------------------------------
Condition
Some 2008-2009 model year Chevrolet TrailBlazer and GMC Envoy vehicles equipped with a 4.2L engine (LL8), may have a condition in which, over time, may develop a crack in the exhaust manifold. If this were to occur, it could result in increased exhaust noise.

Special Coverage Adjustment
This special coverage covers the condition described above for a period of 10 years or 120,000 miles (193,000 km), whichever occurs first, from the date the vehicle was originally placed in service, regardless of ownership.

Dealers are to replace the exhaust manifold if it is determined to be cracked. The repairs will be made at no charge to the customer.

For vehicles covered by Vehicle Service Contracts, all eligible claims with repair orders on or after July 26, 2011, are covered by this special coverage and must be submitted using the labor operation codes provided with this bulletin. Claims with repair orders prior to July 26, 2011, must be submitted to the Service Contract provider.

Vehicles Involved
Involved are certain 2008-2009 model year Chevrolet TrailBlazer and GMC Envoy vehicles equipped with a 4.2L engine (LL8).

Important: Dealers are to confirm vehicle eligibility prior to beginning repairs by using the Applicable Warranties section in the Global Warranty Management system.
 

dmanns67

Member
Apr 3, 2013
32,979
Ohio
I have never seen headers for the Envoy 4.2. Kooks just recently released a header for the TB 4.2 I6 2002-2005. Still waiting to release the 2006-2009. At least you have a warranty replacement :thumbsup:
 

ScarabEpic22

Member
Nov 20, 2011
728
Definitely try the warrany replacement as it wont cost you anything except not using your truck for a day or two.

Me, I knew my 02 was on borrowed time and ordered a Kooks header. Glad I did, when it came back from MT this year, cracked manifold. :thumbsup:
 

Denali n DOO

Member
May 22, 2012
5,596
Welcome to GMTNation :thumbsup:

I hope you get the warranty and your fix is for free...
 

CaptainXL

Member
Dec 4, 2011
2,445
Might want to take pictures of the exhaust bolts with a date stamp. Make sure they are all there. When you get it back check to see all the bolts are back in. Don't let them charge you for fixing broken bolts.
 

DenaliHD66

Member
Dec 4, 2011
597
Are there ANY exhaust manifolds out there that aren't crappy cast iron like the ones from Dorman? Literally cannot find anything else other than them. I am not going to splooge for the Kooks headers.
 

DenaliHD66

Member
Dec 4, 2011
597
Well are these or the Dorman ones at least have an improved design over the OEM ones to make them more reliable?
 

dfc739

Member
Jul 29, 2012
170
Des Moines, IA
DenaliHD66 said:
Well are these or the Dorman ones at least have an improved design over the OEM ones to make them more reliable?

I installed the Dorman about a year ago and have not had any issues. If I recall correctly, most of the new ones are an improved design with more metal around where the collectors converge. This is where my previous manifold had three or four gigantic cracks.

Edit: just read the link provided by CaptainXL, and "The original manifold on these vehicles has a tendencey to crack. This new aftermarket manifold has extra material added to offer more support and a much longer lifespan. Replace your cracked exhaust manifold for the last time with this premium upgraded design."
 

CaptainXL

Member
Dec 4, 2011
2,445
Yep. Been 2 years going strong with this one. Reason I got it is because as you read that it has added material and it was a tad cheaper. But yeah they are probably all improved designs.

It has a lifetime warranty as well. I would make sure that the manifold is actually cracked before ordering. Mine just had a bad compression gasket. So my old manifold is still good. Wanna buy it off me? $30.
 

DenaliHD66

Member
Dec 4, 2011
597
Yeah I am seeing how the Dorman says reinforced steel around the vulnerable parts. Also a review saying the heat shield didn't fit for one guy's application on his '02. Its cheap enough IMO that I'll just get it when I replace my exhaust system.
 

rjpoog1989

Member
Dec 4, 2011
116
Mine is cracked as well. I went with an Eastern Catalytic Manifold that I purchased off of Rock Auto. 5 years 50k warranty seemed good enough, and it wasn't that expensive. GM quoted me $980 for a new manifold through the dealer. I think that's outrageous.
 

Pittdawg

Member
Dec 5, 2011
538
DenaliHD66 said:
Yeah I am seeing how the Dorman says reinforced steel around the vulnerable parts. Also a review saying the heat shield didn't fit for one guy's application on his '02. Its cheap enough IMO that I'll just get it when I replace my exhaust system.

A very knowledgeable member on the OS indicated the problem is with manifold thermal expansion in what he referred to as experiencing thermal shock when they crack, especially in the common down spout. Based on this, I had my new manifold ceramic coated. So far so good.
 

lmcree

Original poster
Member
Mar 22, 2013
14
I took the envoy into the shop today. The dealer is replacing the manifold under warranty.

I had taken the envoy to several places, before i knew about the warranty, for quotes. Of course it was from $600 - $800 (assuming all went well.)

Really glad to have taken the time to do the research.......you all helped me save some money.

Again thanks for the great information.
 

Sparky

Member
Dec 4, 2011
12,927
Excellent. Glad it is covered. Sure beats footing that bill.

Last I checked my 02 still doesn't have a crack somehow. I'm not complaining.
 

TonyT

Member
May 6, 2012
108
CaptainXL said:
But in case you are interested there is a warranty for replacing the exhaust manifold as show below. You need to be within 120,000 miles.
#11150: Special Coverage Adjustment-Exhaust Manifold Warranty Extension - (Jul 25, 2011)
Subject: 11150 - Special Coverage Adjustment - Exhaust Manifold Warranty Extension
Models: 2008-2009 Chevrolet TrailBlazer
Any such for the 2003? I doubt it but thought I'd ask. Stealorship told me it was cracked and offered to replace it when I had them do the gas tank under warranty.
 

CaptainXL

Member
Dec 4, 2011
2,445
TonyT said:
Any such for the 2003? I doubt it but thought I'd ask. Stealorship told me it was cracked and offered to replace it when I had them do the gas tank under warranty.

Sorry, there is no warranty prior to 2008. But if they offered to do it for free then I'd be all over it. From reading a few threads it appears the dealer would charge a pretty penny. I've seen upwards of $900 just for the manifold. You might want to do it yourself if you have experience with such things. Just keep in mind that there is a risk of broken off bolts being left in the head. The very furthest one closest to the firewall (#11) is probably already broken off.
 

lmcree

Original poster
Member
Mar 22, 2013
14
The repair was completed with no issues. Car sounds great ..... drives great. Again, thanks all and look forward to talking soon.
 

DenaliHD66

Member
Dec 4, 2011
597
OK my noise has gotten worse, and its evolved into a metallic rattling sound going out the back of the exhaust pipe. Its basically a knocking sound right near where the cat meets the downpipe. Plus, I seafoamed today and smoke was coming out from under the heat shield. Misfiring is still present too.
 

CaptainXL

Member
Dec 4, 2011
2,445
DenaliHD66 said:
OK my noise has gotten worse, and its evolved into a metallic rattling sound going out the back of the exhaust pipe. Its basically a knocking sound right near where the cat meets the downpipe. Plus, I seafoamed today and smoke was coming out from under the heat shield. Misfiring is still present too.

Keep Seafoaming it. All your gonna do is plug up the cat. That stuff is nothing more than isopropyl alcohol, some naptha and 60% oil.

Yes, it's mainly oil. Makes a nice smoke screen though.

http://www.mta.ca/administration/fa...Engine treatment - SeaFoam Sales Co. 2010.pdf

Your better off using GM Top Engine Cleaner, Berryman B12, BG 44K or Kreen

If you have a rattling sound out the back of the exhaust then something is loose. Could be the catalytic converter substrate rattling around or the heatshield. Would need to take an upclose look.
 

DenaliHD66

Member
Dec 4, 2011
597
Local BG dealer never got back to me and today was a rare day off and I couldn't wait around to get the BG engine flush. I kinda figured they wouldn't contact me, I need to find a retailer online.

I drive 60 ish miles a day... can I push my luck and drive it until I can get it further checked out/parts ordered? Its misfiring about once a second.
 

dfc739

Member
Jul 29, 2012
170
Des Moines, IA
DenaliHD66 said:
OK my noise has gotten worse, and its evolved into a metallic rattling sound going out the back of the exhaust pipe. Its basically a knocking sound right near where the cat meets the downpipe. Plus, I seafoamed today and smoke was coming out from under the heat shield. Misfiring is still present too.

Wait, you're misfiring? Did it throw a code? You should probably get that worked out first considering it'll eventually destroy your catalytic converter. Which heat shield was smoke coming out during seafoaming? I agree with CaptainXL about seafoam. My opinion, which does not reflect the opinion of this site or any of its other users, is that it's snake oil. It makes a nice smoke show when fed in through the vacuum, but I could not tell a bit of difference. Maybe it works when put in gas, I don't know. I couldn't tell any difference there either though. If seafoam wants to prove their product is good, there are plenty of junk engines they could pull and do a tear down with before and after pics. But I haven't seen any.
 

sLAsh

Member
Jan 26, 2012
39
Add me to the cracked manifold club. As far as I can tell all the bolts are still there.
I was thinking about heating up the last bolt or having the engine hot before trying to take it out. If it doesnt soften the locktite its more likely to strip out the threads but I would rather retap the hole than have to try and drill it out. I know with one of my old paintball markers the manufacturer used red locktight on the bolts and the only way to undo them was with a little heat.
Right now I am just soaking the bolts with PB blaster so I would love to hear from anyone else that tried heat on these bolts

Here's an interesting post I found regarding heating a bolt up and then applying beeswax to break the mechanical bond when dealing with red locktite. Anyone ever try this? http://www.practicalmachinist.com/vb/general/red-loctite-question-190683/
 

dfc739

Member
Jul 29, 2012
170
Des Moines, IA
DenaliHD66 said:
Confirmed, manifold is leaking. Does the Dorman exhaust manifold come with a new set of bolts, or do I need to buy those separately?

Manifold:
Amazon.com: Dorman 674-777 Exhaust Manifold Kit: Automotive


Bolts?
Dorman 674-014 AutoGrade Exhaust Manifold Hardware Kit : Amazon.com : Automotive


Man I so wish I could just drop the money for the set of Kooks. But then my exhaust manifold would be worth 1/6th of what my entire truck is.

My Dorman came with the bolts that connect the main pipe to the catalytic converter, a new heat shield, and the gasket between the head and collectors but not the bolts that attach the manifold to the head. I can't remember the thread size now, but you need grade 10.9 bolts. There is a set that comes directly from GM that has the red threadlocker already applied but they are pricey. I've been using some without the threadlocker with no problems for about a year now. You'll probably also want to replace the donut gasket between the main pipe and catalytic converter so pick one up. Make sure to read up on doing this. There are many threads here and at the old site about this problem. These bolts are notorious for breaking off in the head.

I'm there with you on the Kooks header. A few dyno tests and some more expendable income would probably push me to get it.
 

CaptainXL

Member
Dec 4, 2011
2,445
DenaliHD66 said:
Ordered the manifold, didn't purchase any bolts. Hopefully that's all I'll need....

You will also need a new metal compression manifold gasket and doughnut.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
dfc739 said:
There is a set that comes directly from GM that has the red threadlocker already applied but they are pricey.
I strongly recommend not cheaping out on the bolts or the factory-recommended/applied threadlocker. I never want to touch my new manifold again.
 

mrphoenix80

Member
Jan 1, 2013
251
Plus replacing the old weak bolt with the new expensive ones is cheaper and easier than removing one of the old ones that broke off in the head.:yes:
 

DenaliHD66

Member
Dec 4, 2011
597
Can I get a link to the gasket(s) I need and bolts? Manifold comes with a head-to-manifold gasket.
 

CaptainXL

Member
Dec 4, 2011
2,445
Yes, its in that picture. However if that is the Dorman I wouldnt get it unless it has a lifetime warranty. Get the one I got from APDTY.com instead.
 

DenaliHD66

Member
Dec 4, 2011
597
Already ordered from amazon. It should be arriving today. I need to order the 10.9 bolts now too.
 

CaptainXL

Member
Dec 4, 2011
2,445
OK but you might want to consider returning it if the warranty is not lifetime. I have read some reviews that the Dorman cracks again just like the factory one right after the one year mark. There are also complaints that it isn't made well.
 

Forum Statistics

Threads
23,483
Posts
639,847
Members
18,715
Latest member
ozzyextlt

Members Online