Exhaust Manifold Leak (Suspected): Tips, Suggestions, Experience?

[Charlie207]

There are various grades of stainless steel; I wish Dorman would specify more specifically what they're made of.

Well I'm 99% confident it's not in the same universe as the stainless I used to mill down into landing gear. They are probably at least 5% marshmallow mixed in with the iron, cobalt,and nickel.

 

[Charlie207]

so I can't find what I'm looking for, but I also didn't realize what arp is calling stainless steel header bolts/studs is 170k psi. that's some specialty stuff, I'm not sure there's much stainless about that metal besides not rusting lol. but seem like good stuff. personally I'd like a hex tip to the stud to help install and removeal, they come in handy and a crimp style lock nut, and not huge fan of 12 point since I don't have any 12 point sockets. well a few. but they seem to be a high rated strong stud.


this more what I'm use to for stainless


"The hardest and strongest of the hex bolts

Despite the popular belief, a stainless steel bolt is actually weaker than a grade 8 bolt. In fact, according to the Society of American Engineers (SAE), grade 8 bolts are the strongest and hardest hex bolt you would want to use in constructions or the automotive industry. While the carbon alloy bolts have a proof load of over 120,000 psi, their stainless steel counterparts don't carry an indicative proof load. Moreover, the minimum strength of grade 8 bolts is around 130,000 psi, whereas stainless steel strength doesn't exceed 90,000 psi."

grade 8 being about metric grade 10.9. the dorman studs have a 10.9 grade nut on them, so I'd hope the stud is rated the same. they aren't stainless steel because a magnetic will pick them up, just plated with something so they don't rust. probably zinc.

A Mini Guide On Grade 8 Bolts — Melfast

Grade 8 bolts are specified for high strength applications and are commonly used in heavy manufacturing, such as tractor and truck fabrication for instance. The bolts are typically made of a medium carbon alloy steel that is plated in zinc for extra resilience. The grade 8 bolt can be identified via

www.melfast.com

so yeah, it seems what arp is calling ss is very strong by the psi they give out.


either way, totally your call. I'd get that stethoscope and see if you can find the leak. it could be at the collector forsure. from the video that can definitely be an exhaust leak as it seems to go away as it warms up and everything expands. I'd personally confirm before taking everything apart thou but if you don't mind the work and money, definitely can't hurt

I'm sure they want to balance out the threat of shredding the tiny threads in the cylinder head if they used super steel hardware.

 

[petethepug]

08 Yukon w/ 5.3L. I didn’t read past posts thoroughly so if somethings already covered, that’s why.

On my 08 YXL 6.2L I verified no codes present, plugs replaced with OEM. The tick was still there. Had the Mani off for the AWD 100k Maj serv when trans was pulled. Yup, two broken studs. One took 2 hours to extract.

I didn’t know about the ARP Mani studs at the time or I would of installed them. On our Alum heads Stainless probably not a good idea as it reacts with Alum to create red oxide. Salt speeds the process.

When the job was done, the tick was better. New plug wires really helped and stopped it except when it was below 50*F on start up. What I was left with was GM’s infamous “piston slap” that occurred on the Gen 4 V8’s.

Piston slap can be unnerving when it’s really cold but ultimately harmless. Carfax recently emailed me that my 08 Denali has over 240k on it with regular jiffy lube changes. I sold the truck in 2020.

I’d do the ARP standard studs for just a bit more cost. Obviously reusing the old studs is asking for trouble on Aluminum heads. One broken stud can cost you $250 in labor depending where it snaps.

 

[solli5pack]

Might be worth to take the serpentine belt off and start the truck to make sure the noise isn't coming from one of the engine accessories...

 

[GranPrix]

just checking, the torque specs is 18 ftlbs?

 

[Eighthtry]

For what it is worth, I noticed two broken front exhaust manifold bolts on the driver side of my 11 Yukon Denali. This is a common problem. I had no symptoms, just noticed them while changing oil and doing a visual inspection while under them. It is easy to inspect because I have a lift.

I will do a bunch on a truck, but I am not about to tackle two broken bolts. Took them to a highly competent local auto repair facility and they got them quickly fixed. I do not remember what they charged, but I do remember I thought it reasonable. So reasonable it was the perfect executive decision to get them to do it rather than me reinvent broken bolt removal.

Use grade 8 bolts. I'm not sure what the rest of the ti and ss discussion is about. Grade 8 bolts have been used next to forever with unbelievable reliability to the point that no one ever has discussion unless there are looks involved. GM just ended up with a batch of bad bolts. There was nothing in that engine compartment that ever had looks.

Now I do consider looks are important in my wife. So I will consider ti and ss if I am forced to put her back together.

 

[CruelJung]

just checking, the torque specs is 18 ftlbs?

Yes, but that's the final torque spec. Moving from the middle bolts outward, alternating left/right, you make two passes. Pass one is 11 ftlbs and pass two is 18 ftlbs.

 

[CruelJung]

For what it is worth, I noticed two broken front exhaust manifold bolts on the driver side of my 11 Yukon Denali. This is a common problem. I had no symptoms, just noticed them while changing oil and doing a visual inspection while under them. It is easy to inspect because I have a lift.

I will do a bunch on a truck, but I am not about to tackle two broken bolts. Took them to a highly competent local auto repair facility and they got them quickly fixed. I do not remember what they charged, but I do remember I thought it reasonable. So reasonable it was the perfect executive decision to get them to do it rather than me reinvent broken bolt removal.

Use grade 8 bolts. I'm not sure what the rest of the ti and ss discussion is about. Grade 8 bolts have been used next to forever with unbelievable reliability to the point that no one ever has discussion unless there are looks involved. GM just ended up with a batch of bad bolts. There was nothing in that engine compartment that ever had looks.

Now I do consider looks are important in my wife. So I will consider ti and ss if I am forced to put her back together.

I would probably be thinking the same, regarding the breaking of bolts, but my engine was removed for a DOD/AFM delete in 2020. I may still soak the bolts before attempting removal, but I at least know they've had less than 17 years to conjure the strength for stopping me.

 

[CruelJung]

I would just install new MLS (multi-layer steel) manifold gaskets, and new bolts or studs, and call it a day.

Shorty headers provide zero performace gain over the factory LS cast manifolds. So, unless you want the look or sound (might do something?), then you're just burning money. Long-tube headers DO give you a big performance bump over OEM manifolds, but then you'd need to dump a lot more $$$ into a revised tune, and reusing or buying new catalytic converters. Texas Speed, among other spots sells a full header w/cats & Y-pipe kit, but your gonna spend over $2k.

These are the stainless Dorman studs I used, and needed 2x kits from the Jungle website: https://www.amazon.com/dp/B0BHZYNW7W?ref=ppx_yo2ov_dt_b_fed_asin_title

For years I used the Dorman exhaust leak clamps on my 5.3, because I had a bunch of broken manifold bolts. The clamps helped make most, but not all, of my cold-start ticking go away. I should have just replaced the manifold gaskets, but I was scared of breaking all the bolts. Funny thing is, when I pulled that motor they all came out fine, even the broken bolts that stuck out of the cylider head. I was able to clamp some vice grips on them and wiggle them out.

I appreciate the advice about the headers and manifold bolts. If I went the shorty route, it would only be for looks, sound, and general refusal to put cast iron back on my heads IF my current manifolds needed to be replaced. Also, with my long term performance upgrade thoughts/plans, I don't know what I want my exhaust to be so I would rather not invest in something requiring a tune right now.

 

[CruelJung]

so I can't find what I'm looking for, but I also didn't realize what arp is calling stainless steel header bolts/studs is 170k psi. that's some specialty stuff, I'm not sure there's much stainless about that metal besides not rusting lol. but seem like good stuff. personally I'd like a hex tip to the stud to help install and removeal, they come in handy and a crimp style lock nut, and not huge fan of 12 point since I don't have any 12 point sockets. well a few. but they seem to be a high rated strong stud.


this more what I'm use to for stainless


"The hardest and strongest of the hex bolts

Despite the popular belief, a stainless steel bolt is actually weaker than a grade 8 bolt. In fact, according to the Society of American Engineers (SAE), grade 8 bolts are the strongest and hardest hex bolt you would want to use in constructions or the automotive industry. While the carbon alloy bolts have a proof load of over 120,000 psi, their stainless steel counterparts don't carry an indicative proof load. Moreover, the minimum strength of grade 8 bolts is around 130,000 psi, whereas stainless steel strength doesn't exceed 90,000 psi."

grade 8 being about metric grade 10.9. the dorman studs have a 10.9 grade nut on them, so I'd hope the stud is rated the same. they aren't stainless steel because a magnetic will pick them up, just plated with something so they don't rust. probably zinc.

A Mini Guide On Grade 8 Bolts — Melfast

Grade 8 bolts are specified for high strength applications and are commonly used in heavy manufacturing, such as tractor and truck fabrication for instance. The bolts are typically made of a medium carbon alloy steel that is plated in zinc for extra resilience. The grade 8 bolt can be identified via

www.melfast.com

so yeah, it seems what arp is calling ss is very strong by the psi they give out.


either way, totally your call. I'd get that stethoscope and see if you can find the leak. it could be at the collector forsure. from the video that can definitely be an exhaust leak as it seems to go away as it warms up and everything expands. I'd personally confirm before taking everything apart thou but if you don't mind the work and money, definitely can't hurt

Thank you! I greatly appreciate your depth of knowledge on this!

I took my stethoscope above, around, and under my idling vehicle--tracing the exhaust. Although my methodology might have been less than great, I did not gain any clarity on the sound. I did take some more images of soot I found, though, as well as the current bolts and gasket--quick side note on this: my AFM was deleted in 2020, so these bolts were taken out and two of them on the passenger side are different/newer than the rest. There's more to unpack about that delete, but I am thinking my current exhaust manifold gasket is some kind of composite (although with a metal layer on the manifold side?) that came with the delete kit, which I think might have been Texas Speed because I know it's a popular option and its kit images look to have a similar 'stamped' looking exhaust manifold gasket. Ultimately, though, I don't have a record of the product used and the job was wrapped up in my vehicle purchase back when I was almost entirely automotive-ignorant--didn't ask the questions when the information was available.

I got the bolts (ARP 134-1102, chromoly, hex) and the gasket (Mahle, MLS), but I will make another post in this thread about that with some questions about procedural options.