Exhaust manifold broken bolt replacement....... 2012 Dodge Ram

[Charles scozzari]

I'm a company mechanic in the salt belt. While I do some retail, most of my work is in house. I fix things every day that simply could not be fixed at retail. I've done a lot of this type of work. I'm not a machinist... I just stuck a lathe in my basement, so I soak up a lot of stuff here that I'm in no position to reciprocate. So when I stumble on something that is within my depth.... I try to offer solutions, as well as reasoning. Even if it's beyond the immediate need, it will be searchable, and probably applies to a lot more than the immediate need. So thank you as well, for all the stuff you've put up here that might be nothing to you, but I will search and find one day.


It's not the right answer. The bolts will not freeze in place if you use the copper, but if you have to do this again in due time, which is not uncommon, you'll find that the aluminum holes are corroded back. Enough to matter? Crystal ball? The chemistry escapes me to some degree, but you have dissimilar metals-giving a galvanic "situation" there. Adding the third (the metal in the anti seize becomes a third dissimilar metal. Plus we add our own electrical current, so it gets crazy, way beyond any galvanic compatibility charts. At a level that's way over my head, there's several ways to use that situation to your advantage, be it to "moderate" a galvanic reaction, to act as a sacrificial anode, or to just be so "wrong" that it makes a damaged which is guaranteed to be softer than the parent metals. At a level that's not beyond me, nickel won/t damage the aluminum, and "eventually", and that's use case and environmental conditions, the copper will. Eventually. The next time apart, the aluminum holes would probably accept a new bolt, but the threads, probably still intact, will be eroded back such that they're oversized, with poor engagement. Excellent chance that they won't take torque when they are tightened at that next go-round.

How long are you gonna keep this? How fast did it rot the first time? Are you the first, or has this been done before? I see you found anti-sieze on the stuff you removed.... Somebody's been there. That's NOT factory on anything. Ever. Copper is better than nothing, as heli-coils are so easy to pop into an aluminum head, in situ, provided you have correctly placed holes (which you will). And they are a sound repair, with a stronger and more durable joint than the original. They're very very forgiving about some slight angular misalignment from the awkward manual drilling and tapping. And typically (I know folks hate to hear this.....), typically they have a similar pull out force than the time sert type (solid) inserts do in an ideal situation, but freehanded, with some ever so slight misalignment (or just crazy crooked if you like), the heli-coils shine above. So if you add in the "by hand" factor, and the solid inserts are not as good as the original. But anyhow, it's VERY repairable at a very low cost if you have no other choice, and of course that will apply if you have to go in again. The biggest risk being a straight up mistake with the drill. If you use copper, and you leave the new hardware there forever,t and never have to revisit this...... Just like original half failed hardware, you could never set up a "new" joint with it, but it worked fine as is, after the head, manifold, and gasket all got to know each other via some years of service and heat cycling. It's not gonna fall off. Not for that reason anyhow. The point of that being, recovering from "wrong" is a real thing, more work, more time, etc. but it is NOT something that's going to take the next repair to the next level in any way. It's very, very recoverable with no unreasonable extra tools or skillsets. So in my mind, it becomes a judgement call on your part. What are the odds you'll do this again? And can you fire in a heli coil freehand and get it kinda close? (If you got this far... I bet you could fire in a heli-coil freehand and get it kinda close...). So yeah.... Judgement calls and speculation sometimes come into play in that situation. If you have cause to live with a compromise, and a risk (not guarantee) of future with some known degree of managable (but real) aggrivation... Well..... There you go. Measure with a micrometer, mark it with a crayon, and cut it with an axe. If it has to get done, it has to get done.

One other thought I'm having... You might know this. I "assume" that you're going to torque these fasteners with a carefully calibrated click elbow, right? If so, (assuming it's an experienced click elbow) you'll probably be fine, but if you're actually gonna click the hardware like you oughtta.... Whatever brand of anti-sieze you have is gonna have published nut factors (K factors) for adjusting the torque. It's likely be something in the neighborhood of half to two thirds of the "standard" torque. That stuff is GREAT for fooling you into over stretching bolts, and with the uneaven heating/cooling of that area, and the very different coeficient of expansions.... Pay attention, and while it is a joint that abuses it's fasteners tremendously, it's low force (in the big picture), so if you know about it, you'll probably be plenty close enough.

Don't ya just love cast iron heads, little thread sealant maybe some Loctite and your'e good to go. Charlie.

 

[brino]

Two in the last three years. I wouldn't have done it once if I had a choice.

@sdelivery

What I am trying to determine is if spending today setting the manifold up on the mill and flattening the mating face is worth the time and effort.
It might mean booking tomorrow off work for re-assembly.
ie. Does the extra effort pay off in the long run?

Did you have to do the same manifold on the same vehicle within three years even after milling it flat the first time?

Thanks,
Brian

 

[Charles scozzari]

Alum. heads will always cause problems. The only reason I believe they resurfaced today is to reduce total weight of the given vehicle for better gas milage. G.M. used them in the early 60s on the intermediate models and they were problems then. But then you were able to work on your own cars and you had the room to do what ever was needed. Now you open the hood and don't even see the motor which is what it's all about. Now it has to go back to the manufacturer and if you do something that effects the computer your dead in the water. So doing work on, or replacing cylinder heads today is almost out if the question. The only place I agree with using them is on a race motor where you can work on them with no problem. I don't know what the answer is going to be but there is really no choice. I really don't see any advantage with other than weight reduction.

 

[Flyinfool]

The warping of the manifold happened after it was installed. The bolts were able to hold it because they were already tight. to reinstall that warped manifold the bolts may not be able to pull it back to flat and you can end up with leaks. I would flatten it. Yes it will warp again but it will be held in place by the bolts.

It is not the warping that breaks the bolts. it is the difference in thermal expansion that is breaking them. The aluminum in the head will expand a little more than double what the cast iron will. When you look at the end bolts it is that difference in expansion that is literally bending the bolt back and forth until it fatigues and snaps. every single time those part heat up they bend the bolt, and every time they cool off they bend the bolt back the other way. Every brand has this issue. For my Chevy there are after market brackets that bolt to the front and back of the heads using existing factory holes (the factory used them as lift points to set the engine in the frame) and wrap around to the manifold so that you do not even use a bolt in the outer most holes of the manifold this clamps down the end of the manifold just as tight as the bolt would have but allows the manifold to move back and forth under the clamp, you will never have a broken manifold bolt again. In time the new bolts will break again. I do not know if there is such a thing available for ford or dodge or if ford or dodge even have un used tapped holes in the heads to attach such a thing.
You could be proactive and just replace all the manifold bolts every 5 years. If you pull and replace one at a time it should not need a new gasket.

 

[Charles scozzari]

Can, or could the antioxidants for use on alum. electrical wire connections work or help. My house was being fed with alum and it seemed to work in that application.( I did however remove the alum and replace it with copper. ) ????????

 

[Just for fun]

I would resurface the current manifold. I don't see any reason to replace it.

 

[Charles scozzari]

I would resurface the current manifold. I don't see any reason to replace it.

The only thing I wonder is if after you take a truing cut what if the head is untrue and you tighten the bolts is there a possibility of pulling a thread ?

 

[Just for fun]

The only thing I wonder is if after you take a truing cut what if the head is untrue and you tighten the bolts is there a possibility of pulling a thread ?

I wouldn't think that would be the case, but I don't have any experience with aluminum heads. Even if it wasn't true, wouldn't you think that the low spot would be where the manifold was loose allowing movement of the manifold. In my mind trueing the manifold couldn't hurt.

 

[Charles scozzari]

I wouldn't think that would be the case, but I don't have any experience with aluminum heads. Even if it wasn't true, wouldn't you think that the low spot would be where the manifold was loose allowing movement of the manifold. In my mind trueing the manifold couldn't hurt.

Yes, I was thinking maybe the center might be high and tightening either end might pull threads. The truth of the whole conversation is new gaskets with some Form-a-Gasket and bolt it back up. Done. I'm over here yapping and brinos out driving around, no leaks no oder. All kidding aside, I hope all went well. Charlie.

 

[RJSakowski]

I wouldn't expect much in the way of thermal expansion of the head. Aluminum is a great conductor of heat and the head temperature won't be much above the coolant temperature. The cast iron manifold on the other hand is a relatively poor thermal conductor and is subject to exhaust temperatures and will experience significant thermal growth. At those temperatures, the manifold can ineleastically deform and as it cools back down, it will warp.The bolts will restran the manifold against the warp, causing an elastic deformation at the expense of added strain on the bolts, eventually causing their failure. Once they fail, there will be a gap created by the unrestrained warp which will be most noticeable with a cold engine.