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Old 05-01-2010, 01:26 AM   #1
Andy Griffith
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Default GM 6L exhaust manifold and bolts

So there I was changing the plugs and wires on my 2000 GMC Sierra 2500 6L with 95K today when I get to the front plug on the drivers side and see this sitting on top of the plug wire heat shield.



Seems the manifold bolt decided to snap off flush with the head. Closer inspection of the manifolds revealed not only the front drivers side bolt broken off but the rear drivers side and rear passenger side bolt heads were missing as well. Further inspection revealed what looks like the passenger side manifold cracked in half at the midway point. Looks to me like it may have been this way for some time.



The truck has had what sounds like a lifter tick when cold for the last year or so that goes away when the engine is warm. I don't hear or smell any exhaust leak and the tick doesn't sound like an exhaust leak such as you would hear from a hole in an exhaust pipe or header. Is it possible that sound is coming from the exhaust manifolds?

I'll have to try and get a lighted inspection mirror in there tomorrow and see if I can have a look in the two back holes to determine whether those bolts broke off flush with the head or not. The two back holes on each side are somewhat behind the firewall into the tunnel, and access is going to be difficult to remove the broken bolts from the heads. Maybe there will be a bit of bolt left sticking out of the head that could be grabbed with vice grips.

The exhaust manifolds on this truck are are rusty but the rest of the truck is pretty much rust free. Is the rusty/breaking bolts an issue with these GM engines?

Thanks
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Old 05-01-2010, 01:56 AM   #2
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Default Re: GM 6L exhaust manifold and bolts

I can tell you that without exaggeration, every 6.0L that I've run across including mine tick until they warm up. The 5.3L do it too, just not quite as bad. I'd check out the manifold, but the tick isn't anything to worry about IMHO.
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Old 05-01-2010, 02:11 AM   #3
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Default Re: GM 6L exhaust manifold and bolts

The "crack" in the manifold is an expansion joint, normal, the rust is nothing to worry about, the tick in the motor may be normal, alum motor expands more while warming up than cast iron, and has more clearance cold. The broken bolts...it may be easier to r&i the heads to get the back bolts out, if it isn't leaking...depends on your skill with a right angle drill and left handed bits.
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Old 05-01-2010, 04:54 AM   #4
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Default Re: GM 6L exhaust manifold and bolts

Quote:
Originally Posted by Andy Griffith View Post
The truck has had what sounds like a lifter tick when cold for the last year or so that goes away when the engine is warm. I don't hear or smell any exhaust leak and the tick doesn't sound like an exhaust leak such as you would hear from a hole in an exhaust pipe or header. Is it possible that sound is coming from the exhaust manifolds?

Absolutely!!
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Old 05-01-2010, 05:35 AM   #5
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Default Re: GM 6L exhaust manifold and bolts

My 2006 6.0 liter has at least one broken exhaust manifold bolt, I think its pretty common and not an easy fix
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Old 05-01-2010, 05:52 AM   #6
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Default Re: GM 6L exhaust manifold and bolts

I guess I should go and take a look at my exhaust bolts on my 2006 6.0. I still have a few years on my extended warranty to get it fixed.
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Old 05-01-2010, 06:59 AM   #7
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Default Re: GM 6L exhaust manifold and bolts

I think the Hypereutectic pistons with short skirts in those engines are known for cold tick. They are like forged pistons in that they don't expand as much and will have mild piston slap until warm. If I remember correctly, those motors have roller lifters so the tick is probably not the lifters.

IMO, I would not consider trying to fix the broken bolts unless you are aiming to pull the head(s). Drilling a good repair on the vehicle is going to be VERY difficult.
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Old 05-01-2010, 10:10 AM   #8
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Default Re: GM 6L exhaust manifold and bolts

I have a set of manifolds for a 6.0 with 29k miles on them if you need some.
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Old 05-01-2010, 11:14 AM   #9
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Default Re: GM 6L exhaust manifold and bolts

Ive seen so many with this problem. Pull the manifold and weld a nut to the broken off bolt. Ive fixed 4or5 like this. ARP fasteners make a stud kit for the manifolds. Never had problems after that.
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Old 05-01-2010, 11:47 AM   #10
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Default Re: GM 6L exhaust manifold and bolts

What are the chances the rest of the bolts come out? if you already have some broken. Thats what keeping me from fixing the bolts on mine. Plus it isn't leaking yet so why bother
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Old 05-01-2010, 12:32 PM   #11
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Default Re: GM 6L exhaust manifold and bolts

If you have broken bolts yes its most likely that the tick is an exhaust leak.

My MIL has a 94 buick with the lt1 with broken manifold bolts and it ticks until its warm. It would cost more to fix then the car is worth so they just tick away.
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Old 05-01-2010, 06:31 PM   #12
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Default Re: GM 6L exhaust manifold and bolts

If you're going to pull the manifolds, soak the crap out of the remaining bolts with some PB blaster or similar penetrating oil. Spray and soak them a few times that way you don't break any more bolts.
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Old 05-01-2010, 08:36 PM   #13
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Default Re: GM 6L exhaust manifold and bolts

I saw a 6.0 with 3 bolt holding the manifold on. It was leaking like crazy. Spend the 80 bucks on good studs and never do it again.
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Old 05-01-2010, 08:47 PM   #14
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Default Re: GM 6L exhaust manifold and bolts

Quote:
Originally Posted by Andy Griffith View Post
The truck has had what sounds like a lifter tick when cold for the last year or so that goes away when the engine is warm. I don't hear or smell any exhaust leak and the tick doesn't sound like an exhaust leak such as you would hear from a hole in an exhaust pipe or header. Is it possible that sound is coming from the exhaust manifolds?
Yes, the ticking noise is one symptom from a leak at the manifold.
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Old 05-01-2010, 09:33 PM   #15
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Default Re: GM 6L exhaust manifold and bolts

I have 2 GMC's one 4.8 and one 5.3. No broken bolts that I have seen. Everyone I know with these engines has the noise when they are cold. I have always attributed it to piston slap. It's a classic scenario...engine cold, it sounds like a diesel, within a couple of minutes perfectly quiet. Between these engines I have about 350,000 miles. If I were you I wouldn't worry about the noise and don't be dissapointed if you do fix the manifold probelm and the noise remains.
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Old 05-02-2010, 10:32 AM   #16
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Default Re: GM 6L exhaust manifold and bolts

^^^almost every 4.8 5.3 5.7 6.0 even the 8.1 does it. I thought it was a lifter or something else. But everything has been fine for the last 95k
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Old 05-02-2010, 12:15 PM   #17
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Default Re: GM 6L exhaust manifold and bolts

cold start lifter leak down to help cold start emissions ..like a rhoads lifter
no problem
I have only seen 99-2000 iron head 6.0s break the bolts
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Old 05-02-2010, 07:34 PM   #18
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Default Re: GM 6L exhaust manifold and bolts

Common for them to break on trucks and SUVs. Seen lots of them through the 4.8/5.3/6.0 engines, especially with higher mileage.
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Old 05-03-2010, 01:12 PM   #19
Andy Griffith
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Default Re: GM 6L exhaust manifold and bolts

Thanks for the replies, I think you guys are probably correct, the ticking noise the same ticking noise that has been present since the truck was new.

The truck has been sitting in the shop for last three days while I changed plugs and did some other maintenance. I was going to try and listen for an exhaust leak when I fired it up last night but of course the tick was barely audible that time. Other times it has been more pronounced. I listened around the exhaust manifold and broken bolts with a stethoscope but it all sounds the same.

Guess I'll wait until the exhaust starts leaking for real and then do something about it. I was able to verify that the rear bolt on the drivers side looks to have broken at the bolt head it there is a stub of the fastener sticking out of the head. This might be hope for turning it out with some vice grips when the time comes, if it doesn't snap off again. The rear bolt on the passenger side does not sit quite as far back behind the firewall but it looks to have snapped off flush or below the head surface. My 45 degree drill sort of fits in there but it would have to be a very short drill bit. At any rate that is going to be a time consuming job when time comes, especially if the heads need to be removed.

I was a bit discouraged when I found the broken bolts as I really need to get another 10 years/ 100K miles out of this truck if at all possible. It has been well maintained and lived a fairly easy life, but maybe I'm expecting too much for a modern vehicle to go 200K.
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Old 05-03-2010, 02:49 PM   #20
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Default Re: GM 6L exhaust manifold and bolts

do you have a welder? ive been messing with the lsx series motors for years now and if you weld a nut to the broken stut it will back right out. Your talking about a 4 hour job here both sides. If you dont fix it watch for leaks if the leaks get too big it will throw off the o2 sensors readings.
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