What is causing exhaust manifold bolts to break on the 5.7?

My 2014 ram 5.7 has broken exhaust manifold bolts on both sides. I fixed the right side about 6 months ago now the other side is broken. Does anyone actually know what it causing them to break? I heard it was the manifolds were warping. The last manifold I recently bought was on backorder. The dealer said the manifolds were on hold by the manufacturer for redesign or something. I wonder if the new manifolds will be any better?

I had the same problem on my 2004 Ram 2500 5.7. I replaced all the bolts and had the manifold machined. So far so good it's been about 2 years. They all do it. Cheap China Casting I guess.

I did know the 5.9 engine was bad for that, i didn't know the 5.7 was too. ...........to small ! on the bolt side.

I'm thinking more environmental. You 2 as well as I are in the rust belt/ snow belt area of the country. I have replaced manifolds on several brands of trucks and the common factor is rust. Ford manifolds will actually rust through but all suffer rusted bolts, rusted castings. The castings cause "rust jacking " where they expand under the bolt and pop the heads off.

Anyone from a rust free area have broken bolts?

It happens down here too. Had a friend w/ a 5.7 hemi that kept breaking exhaust manifold bolts. This was over 10 years ago.

The two of the bolts on my right side were broken. They weren`t rusted. They were stainless OEM for those two positions.

This is why, many of the older guys in the industry like my Dad, when OEMs started to change to metric in the late 70s,
fought it tooth and nail and complained to the powers that be.

Because his associates and he knew the finer increments of metric fasteners would allow Engineering to eventually reduce mass and cost to the point vehicles
would make it to 3-36, and after that...."hey, who cares? Make money from parts and service! Not our problem anymore".

This is what we have to work with....Iron manifold, aluminum head, tiny metric fasteners.
Think about expansion/contraction, hot/cold, over and over.
It's just a [censored] combination.

If those fasteners were 3/8" grade 5 or 8, think they'd still break?

Aluminum head, iron manifold expand and contract at different rates and highly stresses the tiny bolts and most of the time it is the end bolts that break because that is where the most difference in expansion and contraction is experienced by the head and manifold.

Yep, the manifold is expanding in length when hot, contracting as it cools. That wiggles the bolt back and forth breaking them.

Funny thing is, Chrysler knew the solution, look at any flat head six, or slant six and you will see that was done to keep those long exhaust manifold from cracking or breaking studs.

My 2105 broke two on the passenger side, fixed under warranty but $200 deductible. Same on the drivers side. Next the passenger side again, but this time they had to replace the manifold also as I was warped beyond repair. Now at 348K and a new engine I hope (also a $200 deductible ) I hope the studs stay in together...

Tap them for bigger bolts 3/8s would hold it

Back in the 60s & 70s, nearly every Mopar motor had cone shaped washers that allowed some movement and expansion due to heat. After they did away with the cone washers, the exhaust bolts started to break.

Maybe add the cone washers back in? I'd suspect McMaster-Carr probably has cone washers in the correct size. Might be worth the investment.

Slant used low torque on the nuts too. 10 ft. lbs.

Are the manifold bolts stainless? If so, you can't harden stainless. They need to be grade 8.

My Ram has had a tick that goes away as it warms up that I've always just figured was a manifold so never did anything about it since I kept hearing about people fixing it only to have it happen again. I know someone who got tired of the repair and put headers on to solve the problem.

My 2014 is in the dealership now for this . Also it’s not mopar specific. Our GM trucks at work have the same issue .
I assumed it was an aluminum head vs cast manifold issue ,

Cone washers make engineering sense.

Using studs where the highest stressed middle is not threaded makes engineering sense.

Not having the end fasteners leave the aluminum cylinder at 90 degrees makes engineering sense.

Not sure Fiat Chrysler engineers left after old guys retired had “engineering sense,
or perhaps brainiac spreadsheet obsessed MBA’s in management never taught whiff of “engineering sense.”

Of course all this now corrected with French top management at Stellantis.

When I was working a repair station on the assembly line in the chassis department I told an engineer of a problem with a part that they had changed and the exact words of the engineer were "As long as it makes it out of warranty, we just don't care"..........

They were all oem bolts but I found out two bolts on the right side ( the ones that broke) were OEM stainless. I found out when I ordered new bolts and there was two different part numbers for that side. No idea why only those two. The left side were all regular Oem steel but three broke on that side also.

I was asking about the manifold because the mopar dealer said the manifolds were on nationwide back order due to a new part number being released so I was hoping it was a change in the manifold design in some way that would help the issue.

"Not having the end fasteners leave the aluminum cylinder at 90 degrees makes engineering sense."



being stupid, i don't understand this part. could you please explain ?
TIA.

I have a 2011 Ram 1500 in NW Iowa (rust belt) and no issues with broken exhaust bolts.
My son's 06 Jeep Commander 5.7 did break some exhaust bolts, but we got them fixed a couple of years ago and no problem since
My other son has an 06 Chrysler 300C with no broken bolts or issues

JS

I have seen the issue more with 2013 and later 5.7's, so I am under the impression it was a change in materials...

Mmm, not really. There are many grades of stainless that can be hardened, example: most or all the trim pieces in your car.

I don't know as though the solution is just because there is a washer there, I think it helps if the bolt is longer... think about bending a coathanger back and forth to break it, if you grab a long section and bend it back and forth a given amount like say 1 foot and bend it back and forth 1 inch it will take forever to break it, now if you grab it 1 inch apart and bend it back and forth about 1 inch it will break pretty quickly, that is what is happening on these hemis, they are short bolts being bent back and forth a certain amount that is much more than an iron manifold on an iron head would be bent, that iron manifold, iron head and long bolts because of the spacers is not really taxing the bolts enough to break them, they are not experiencing as much stress and not on such a short distance. I think a longer bolt and a spacer would reduce the stress and save the bolt even if it was the same material.

My 2006 5.7 never broke any bolts. The manifolds did warp though.

I would think that unless the washers were the cone shaped kind or made to absorb the expansion of the different metals the bolts would be just as likely to break but have a longer area to break in.

They just give a longer bolt that can take the bending stress better, those washers cone type or not don't slide around or anything, if they did they would wear out and loosen up.

Sorry, I should have used more words and written more clearly in that sentence.

It should have read:

Not having the end manifold bolt fasteners thread into bolt holes in the aluminum cylinder head at 90 degree square would be an improvement.

If the end of exhaust manifold bolt holes
and their mating threaded holes in the aluminum metal of the cylinder head
were drilled and tapped at some degree of angle outward,
and the hole in the manifold made oval shaped
(or simply bigger diameter)
the thermal expansion of the exhaust manifold would not result so quickly in
the cast iron of the manifold eventually contacting the bolt threads in a “shearing” type collision
similar to how sheets of metal are ripped in two by metal shop “Shearing Machines”.

“Avoid exceeding maximum allowable shear stress levels to avoid metal failure”

is the modern advice from
3 dimensional principal stress fracture mechanics.

100 years ago engineers thought you could
pull on a bolt too much (tensile stress)
or
push on a bolt too much (compressive stress)

Today it is realized that either
“pure tensile stress“
or
“pure compressive stress”
inherently also creates SHEAR STRESSES inside materials
and importantly these internally created shear stresses
are inclined at various angles
that look “cone shaped” in 3 dimensional view.

When one of these “cones of shear stress distribution”
reaches a certain level
cracks begin growing in size
and the material eventually splits in two.

Too high a “principal” shear stress in one small region
is the “true” enemy.

Three dimensional matrix principal stress analysis
....is the scientific “slang” for this

Works for rocks as well as metals

This is what I have been tryna right here.

Pretty sure it's just the cheapest crap fasteners they could find. Been working with alloy heads and iron manifolds for close to 40 years now and most of the Honda and Toyota cars don't do it

Gus

On the new dt body style ram, 19+ they added tie bars for the manifold bolts, now the manifolds are all cracking. I've replaced a ton of them, both sides

Yup. I never could sell a stock manifold till recently, now they are going like hotcakes, down to my last pair of eagle truck manifolds.

I don't recall the Neon's 2.0 or the K car 2.2 busting off studs, iron manifold, alloy heads

I have a theory that it is low octane fuel , high loading like towing , steep grades or heavy throttle , causes the timing to retard and you get real hot exhaust manifolds. I would run midgrade or higher quality fuel and this problen could be mitigated .

What he said!

If you’ve ever had the manifold off of a Nissan V8 it’s very similar to a Hemi head. Difference being they used a larger fastener in the head. Those manifolds have been cracking for years…..and the cat is integral to it $$$.

as WV said, now the Hemi manifolds are cracking. Easier than extracting broken bolts.

I’ve actually used a step drill bit and widen the end holes on the manifold side hoping that maybe it’ll prevent “shear” and perhaps the bolt will have room to bend some. I’ve also been putting a bead of copper RTV on both sides of the gasket on those end ports. I’ve seen where bolts can be broken, but no leak using that method.

I hear about chronic lifter failures on the Gen III Hemi. And now exhaust manifolds. Does Chrysler have any engineers left in Engineering?

The cone washers do something or they'd never have bothered using them in the past. It's not a bending stress it's more a sort of tensile stress on the bolts from the manifold heating up.

Either way something isn't right with the design. I forget what make or engine it is but for one make their solution was putting in bigger softer bolts because while they were easier to break they were more forgiving to the pressures going on in the application they were being used for.

Install headers instead?

In the early smog years the higher exhaust temps were causing bolts/studs to break. Our fix was to remove them all install new studs (with very light touch of anti sieze into the heads and then the cupped washers and bronze nuts. Check torque after a few heat cyclings and generally the carboning up and re-torque would seal them and the studs would not break.

You are talking about a completely different type of failure here and your reasoning does not apply to this subject, sorry.

It's not just Mopar V-8's. Chevy and Ford trucks have the issue as well. Funny you don't see it in 4 or 6 cylinders engines.
Doug

Oh OK if you say so I trust you.

But let me ask you how come it is almost entirely the end bolts that break? The center ones get just as much tensile stress but I have never seen one of them break and I have replaced 100s of them, the sideways movement is much greater at the ends than at the center, I am sure tensile forces play a part also but that side to side is what finishes them off.

Not to belabor the point, but are you sure that the exhaust flange moves from side to side at the ends but not in the middle? It’s a solid piece of steel and the heat will influence it evenly. I think the end bolts will be stressed slightly differently due to their location, but not in a shear mode, enough to break them.

I am 100% positive the bolts on the end experience more sheer stress than the ones in the center. If the ones in the center move .010 side to side then the next ones move .020 side to side and the end ones will move .030 side to side (ball parking for simplicity sake as it is probably not mathematically exact) because they experience the expansion from the middle PLUS the expansion from the additional length between them and the middle.

i was just thinking about the K car exhaust that had a spring between the manifold pipe flange and the retaining washer and nut.
i wonder if this would be anything to contemplate...........
a longer bolt of better material, a spring close to the shoulder length of the bolt [longer or shorter length of the spring, i can't say] then the cone washer [?] and nut.
just a musing thought rolling around in my noggin.

Well, I couldn`t get two of the bolts out of the drivers side. When I tackled the passenger side myself the broken bolts cam out with the welding a nut trick but these two on the drivers side were broke off too deep. I ended up taking it to a local shop. They had the truck for two days. The said they ordered a special tool for drilling the bolts out. All back together now after $700 . YIkes!

They typically don't break too far down and they generally are not hard to twist out, if they break off flush or just below flush I take a cut off wheel and cut a slot in it (might get the head a little bit so make sure your not aiming your slot toward the port or you'll make another leak path) so I can use a flat tip screw driver to unscrew it. The screwdriver it's elf I will make super flat with a stone of some sort so it bites into the slot real good as the slot comes out slightly rounded in the bottom.

I wonder if any Toyota, BMW or Mercedes exhaust manifold bolts are the same metric size and thread as 5.7 V8 exhaust manifold bolts?

Used that method recurrently and if it did not stop the problem, did a few other mods involving relieving the hole/slot in the manifold casting to provide additional expansion and also taper ground the outward face of the manifold ever so slightly (thicker at the ends and thinner toward the center). The concept of using the bronze is the softer metal allows the cupped washer to slide under heat cycling (put some graphite under the washer).. A few cases I've actually filed the cupped washer to provide a "flat" rather than a cutting edge.
On some motors we have even gone to soft steel studs with a small nick with a hack-saw to give the studs a spot to break above the head surface.
Lots of little movement ultimately breaks steel that is subject to frequent heat cycling.
Some things are impossible to stop (look at aftermarket 4.0 l jeep motors and their aftermarket accordion tube steel manifolds}. Control or allow for movement is key.

Had it happen twice to my 2012 Ram, went to a stainless shorty header and it hasn’t happen again.