Anyone ever hear of this?

[littleblazer]

Hey guys. I have not really a problem since I know what the issue is but rather a curiosity if you will. So a couple of months ago the sierra started ticking. No big deal. I noticed it would nearly go away when warm so I figured it was a cracked manifold since once it got hot the metal expanded and it went away. My dad agreed with that. Fast forward to yesterday, the truck went in for service. 200k tune up, tires, brakes, and a hub was failing. Well we asked him to take a look at it to see what was going on. Well he said two of the bolt heads on the manifold are non-existent.... how that happened I don't know but I don't think anyone has touched it and it's just weird. I haven't looked at it yet but I'll take his word for it. Has anyone ever had this happen? And obviously the fix it to pull, drill and tap. But I'm shocked it goes away if that is true...

 

[Mounce]

Pretty common on 360's. Doubt that it's a rarity on the full sizes.

 

[HARDTRAILZ]

No surprise here at all.

 

[littleblazer]

So the head will just eventually fall off my truck too? I mean I would understand if someone put a wrench on it and snapped it but I guess the heat cycling could stress it enough. Oh well.

 

[Mooseman]

I think it's those crap torque to yield bolts. I got regular 8.8 high strength bolts for mine. Last time I looked, all were still there.

 

[Sparky]

My Trailblazer was missing the bolt heads on a couple of the exhaust manifold bolts. The dealer had replaced all the exhaust manifold bolts on the passenger side of my Silverado before they put it on the lot.

It is a side effect of aluminum heads and iron manifolds with the different expansion rates causing a lot of extra stress on those bolts. TTY probably doesn't help for that application.

 

[MAY03LT]

Yup not uncommon on the 5.3s. Last one we had with back bolt on drivers side had to pull the head. Ida just lived with it.

 

[littleblazer]

I'd imagine the 6.0l is the same as the 5.3 then. Alright so it's just the usual gm problems and not an odd ball one.

 

[Mounce]

From what I've read the 6oh is just a stroked 5.3. Same for 5.3 to 4.8. At least that's what I've understood. Same piston size, longer stroke.

 

[Paul Bell]

This is not a situation that's engine size dependent. It happens to all LS engines with aluminum heads and cast exhaust manifolds.

LS crankshafts are all 3.622" stroke (5.3, 5.7, 6.0, 6.2) except the 4.8 (3.267") and 7.0 (4.125").

 

[littleblazer]

This is not a situation that's engine size dependent. It happens to all LS engines with aluminum heads and cast exhaust manifolds.

LS crankshafts are all 3.622" stroke (5.3, 5.7, 6.0, 6.2) except the 4.8 (3.267") and 7.0 (4.125").

I get that. That's why I said I imagine it's the same. I guess it's better that it's the manifold rather than a head gasket. The ls's are aluminum blocks correct? Well actually I don't believe the sierra is since it's the HD which iirc means cast iron block, but otherwise they are... I know way back aluminum heads used to some what regularly lose head gaskets... but I guess that's ironed out.

 

[Mooseman]

Truck blocks, except for the GMT360/370, are cast iron while cars and GMT360/370 are aluminum. All have aluminum heads.

Anytime you have two dissimilar metals interact with each other, shit happens and breaks. Same thing happened on my 4.2. I had 3 or 4 exhaust manifold bolts that were already broken. When I saw this, I heated the remaining ones with the torch just enough to burn off the corrosion but not melt the surrounding aluminum and they came out without issues. The broken ones I was able to get out by heating the stubs and unscrewing them.

 

[littleblazer]

Especially when the steel doesn't move as much