Broken Exhaust Manifold Studs

Well, I went over our freshly acquired '95 XJ w/201k miles last night. 2.5L I4 w/AX-5 manual trans.

The motor has 3 bolts missings on the intake/exhaust manifolds. 2 of the bolts are on the very ends of the exhaust manifold, which are actually studs.

The one missing bolt, the threads are evident, so hopefully its clear all the way down the bore. Has anyone had a manifold bolt have the tip break off and leave it down the bore? I've never had it happen, if they break its at the surface or farther outside, so hopefully thats the case.

Its hard to see inside the bolt hole on the exhaust manifold, but a little probing seems to show that it ends at the head surface, considering it pretty common for exhaust studs to break, it appears the studs are probably broken off at the head.

Any tips on removing broken exhaust studs out of the head, broken off at the head?

I plan on;
*Pre-Treating the bolts and broken studs with penetrating oil for several days before the job.
*Remove the intake & exhaust manifolds, to get access to the broken studs.
*Drill a Pilot hole in the center of the broken studs, then a larger hole deep enough for an easy out.
*Try to turn them out with an easy out.

Any tips to add to that or a better way? What do I do if this attempt fails?

I don't know much about your case, never experienced that, but I do know if you break that easy out your screwed. I'd think about drilling it right out.

raypla said:

...but I do know if you break that easy out your screwed.

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I've heard of that happening, but how common is it? Doesn't that happen to people that use an easy out that is too small or in an off center hole? I assume if you break the easy out, the tip is jammed into the bolt and is too hard to drill thru?

raypla said:

...I'd think about drilling it right out.

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Never done it successfully, without destroying the threads. How should I approach it?

*Remove the head and give it to a machine shop to use a drill press?
*Use a hand drill and drill successively larger holes up to the threads, and try to clear away the remaining metal in the threads?
*Just drill it out and use a Heli-Core fix kit?

Rick Anderson said:

I've heard of that happening, but how common is it? Doesn't that happen to people that use an easy out that is too small or in an off center hole? I assume if you break the easy out, the tip is jammed into the bolt and is too hard to drill thru?

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everytime i've tried using an easy out, it has broken. i swore them off years ago. it's a great way to make a bad situation worse

Rick Anderson said:

I've heard of that happening, but how common is it? Doesn't that happen to people that use an easy out that is too small or in an off center hole? I assume if you break the easy out, the tip is jammed into the bolt and is too hard to drill thru?

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What happens is the easy out is made of such hard steel it is nearly imposible to drill through.

Rick Anderson said:

Never done it successfully, without destroying the threads. How should I approach it?

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Worse comes to worse you can always drill it slightly larger and re-tap.

Rick Anderson said:

*Remove the head and give it to a machine shop to use a drill press?

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If your not comfortable.

Rick Anderson said:

*Use a hand drill ane drill successively larger holes up to the threads, and try to clear away the remaining metal in the threads?

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Exactly, eventually it will get to the point where it will just fall apart. If you do this I would run a tap to clean it out anyhow.(same size)

Rick Anderson said:

*Just drill it out and use a Heli-Core fix kit?

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Don't have any experience w/these but I have heard good things, maybe someone else will chime in.

I really don't have any experience w/engine rebuilding, but I did race atvs professionally. Having had many experiences w/rebuilding quads and building quads from the groundup I know all about snapping bolts.

First - remove the head. It's damn near impossible to get a good angle on the bolt with the head in place, and this is a job you'll want to do well.

Second on not using the "easy-outs." They usually end up breaking on me as well - and I end up having to use acid or a torch to get the damn thing out. "Hard" in the sense of "glass" - "hard" equals "brittle" with metal. OK on larger sections, not so much on the smaller ones.

MAKE SURE you centre punch the bolt, then drill a pilot hole (not very deep - you're just preventing drill walk,) then go for a full-size drill. There are two ways to do this - either go and get a left-hand tap (they're not quite as hard as EZ-outs, and can therefore take more punishment,) or just centre drill, drill oversize, and install a Heli-Coil. I prefer the Heli-Coil - it's harder to screw up, if you're patient. Threads are 3/8-16.

When you're putting everything back together, use non-ferrous bolts. I like brass or bronze for exhaust hardware - they all but eliminate the seizing problem, and are easier to drill out on the off chance you do break one (which I haven't yet - in 25 years or so.) If you can't source them locally, McMaster-Carr, Fastenal, and MSC Direct all carry them, I believe.

For the studs, you can make them out of brass "Allthread" rod - just cut to length.

USE LOCTITE. LocTite #272 will work for exhaust hardware - and it will also help prevent seizing and galling - which is why exhaust bolts typically break.

Another advantage to using copper-based alloys over iron in high heat? They'll actually get a little stronger with use (not harder - just stronger,) whereas steels will get weaker as they are heat-cycled. BIG plus.

5-90

5-90 said:

MAKE SURE you centre punch the bolt, then drill a pilot hole (not very deep - you're just preventing drill walk,) then go for a full-size drill. There are two ways to do this - either go and get a left-hand tap (they're not quite as hard as EZ-outs, and can therefore take more punishment,) or just centre drill, drill oversize, and install a Heli-Coil. I prefer the Heli-Coil - it's harder to screw up, if you're patient. Threads are 3/8-16.

5-90

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Centre punch is just as important as anything, I forgot to mention that.

Both of those studs were broken off my MJ's 2.5 when I got it also. You can get to the front one easily with a regular drill, but the rear one is a PITA unless you remove ALOT of stuff (brake master, prop valve, booster, and even the steering shaft IIRC). You could try a right angle drill, but you'll have a terrible time getting centered with it. Best way is like 5-90 said and pull the head.

I pulled the manifolds off mine 2 yrs ago to try to fix them, and ended up only being able to retap the front one. I slapped a new gasket on and buttoned it all back up leaving the rear stud still sheared off.....I got lucky and it doesn't leak, and I'm not about to mess with it any more :laugh3: I'm pulling the engine anyway sometime this year for a rebuild (200K) so I'll deal with it then.

Jeff

p.s. If you plan on pulling the manifolds, start compiling a list of new cuss words now so you'll be ready to use them.

If I pull the head, can I re-use the head blots, or do you really need to get a NEW set?

Since its a cam in the block design, pulling the head isn't really that much more after you've got the manifolds off, which I'd have to pull them anyway. Just pull the valve cover, rockers and push rods and then the head bolts. Am I correct in that? How tought to clean up the head and block for a new headgasket after that?

BTW, I've done the intake/exhaust manifolds on my Brothers Wrangler. He had the all too common cracked exhaust manifold/header on the 4.0L I6. The 2.5L seems very similar. We sprayed penetrating lube into the bolts everyday for a week before attempting the job, the bolts all came out easily with no breakage, including the studs on the end of the exhaust manifold. We got new bolts from the dealer, we did not want to re-use the old bolts.

The AMC242 bolts can be reused ONCE - if you find paint marks on the heads, get replacements. If you don't find marks, then MARK THEM so you'll know next time - this is directly from several FSM sets (various years.)

The head bolts are a modified "Torque-To-Yield," and if they're overstressed or reused again, it's entirely possible that you'll have a broken bolt in the block deck to deal with. I'd honestly say it's safer to replace the bolts, if you don't know their history - but if you're sure they've been there since the factory put them in, then just have some bright touch-up paint handy (in the little bottle with the brush,) so you can mark them for later. I find that bright yellow, orange, or red should show through the oil and crud they'll accumulate.

Also, you're right about pulling the head - but have some means to keep the valvetrain parts organised - you'll want to put them back in the same holes they came out of...

5-90

You can reuse the head bolts 1X only. If you find yours have marks on the head (painted) that means they've already been reused, and you'll have to get new ones. If yours don't and you do reuse them, make sure you mark them then so all the world will know :laugh3: If in doubt, I'd just use new ones just as a CYA.
Jeff

damn Jon.....you're fast.....

Yeah - I'm sorting out email for WiP - archiving the last year's stuff and all, and getting ready for taxes (ugh!) So, I'm sitting at two computers right now, and they're both online.

I guess I'm just a "rapid-access cardfile" for engine tech...

5-90