98 ZJ plenum chamber problem - JeepForum.com
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post #1 of 29 Old 09-28-2021, 12:24 AM Thread Starter
giacomom
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98 ZJ plenum chamber problem

Hi all,


1998 ZJ 5.9 , in an attempt to fit the modification of Hughe Engines the 4 bolts at the corners of the intake manifold broke

now I managed to remove the manifold but how do I remove the 4 broken bolts ?
thank you


Giacomo

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post #2 of 29 Old 09-28-2021, 12:34 AM
PolkaPower
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98 ZJ plenum chamber problem

Probably an easy out screw extractor.


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post #3 of 29 Old 09-28-2021, 01:20 AM
LittleFootZJ
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One of mine broke and I had to drill it out. Itís nerve racking but itís doable. Just take your time.


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post #4 of 29 Old 09-28-2021, 04:45 AM
jeepjeepster
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The underside of those bolts are open I do believe. Clean around the bolts and start soaking them in penetrating oil from both sides. It looks like you have a good bit sticking out so I would try some good quality vice grips to start. After that I would personally try welding a nut to them, last resort would be drilling and extracting.

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post #5 of 29 Old 09-28-2021, 06:54 AM Thread Starter
giacomom
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Thank you all,


easy out screw extractor : split inside the left front bolt .......
those bolts are not open at the bottom
cannot be grabbed with some good quality vice grips ........


I have to try to weld a nut to the bolts..


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post #6 of 29 Old 09-28-2021, 07:48 AM
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Yep. In my experience, typically, if the bolt breaks on removal, a screw extractor won't be very effective to remove the threads. Reason is pretty simple, whatever is holding the threads tight (corrosion etc) is strong enough that the original bolt failed before the bond broke. Thread extractors are always weaker than the bolt they are designed to extract. If you don't do anything to loosen that bond, it'll just break the extractor.

Straight fluted thread extractors (not spiral) work better because they don't tighten themselves in and spread out the bolt, and they don't catch the outer threads as bad if you don't drill straight.

In either case, it helps to really clean off the broken end and use a small carbide bit in a dremel to make it flat and make a little divot to start the drill on center. Drilling straight and centered is not easy by hand but can be done. Left handed bits also give you a small chance to catch the metal and have it come out with the drill. People say that if you drill big enough the threads will "relax" or shrink to break them free. I've never seen any evidence of that but the bigger the hole you drill the bigger and stronger the extractor you can fit and if you drill big enough on center you can use a pick to peel the old threads out.

I know this is getting long, but there's more.

One more easy trick is to drill a hole in the center of a short bolt the same thread as the broken bolt and use that as a guide to center the drill.

Welding a nut on works well but will be a challenge here because of the angle of the gasket surface. You'll need to build up the threads enough so the nut can spin. I've recently seen someone use a bit of copper pipe to build up a bolt like this and protect the rest of the piece.

Heat is the best thing to break things free. Acetylene is really required if it's corroded in place. Propane and MAPP torches don't cut it in my experience. Heat and cool a few times with penetrating oil in between. Watch that you don't set the whole thing on fire.

And finally, sometimes nothing works and you'll end up taking it to a machine shop to have it professionally done or install a thread repair kit. To install a thread repair kit yourself you'll want to fab up some kind of jig or use the intake plus a piece of thin wall pipe as a drill guide. As I mentioned before, drilling straight on a angled bolt is hard to do, and installing a thread repair kit at an angle would be bad news.
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post #7 of 29 Old 09-29-2021, 06:28 AM Thread Starter
giacomom
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Hi all, update
I managed to remove 3 bolts by welding a nut on the tip, but the one relating to cylinder No. 1 is impossible to remove .
since I don't want to disassemble the cylinder head, if in that point I put more sealing paste, and I to fit the intake manifold without the bolt, what could happen ?

what should i expect ?
thank you


Giacomo
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post #8 of 29 Old 09-29-2021, 11:24 AM
Timo_90xj
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You can expect both an oil leak and a coolant leak mixing into motor oil through the cylinder block valley.
The problem is the clamping force on the intake manifold: you really need all the bolts and they all need to be torqued to specification if you want things to hold up properly for certain.

Removing the cylinder head doesn't take that long and at this point really is super easy - it's a pushrod engine and you already have the hardest parts pulled out.

1998 Grand Cherokee 5.9 LX daily driver, 1.75" BB, 32" KM2s, HPD30 Eaton e-locker/D44a stock LSD, 4.56 gears, custom- fabbed tube bumpers and tube fenders,...


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1990 XJ (4-door), 4.0 I6, AW4, NP242, PBR 42" tires, Unimog 404 portal axles, 110" WB, full cage + uniframe completely rebuilt, front 3-link + panhard / double triangulated 4-link rear,... ***SOLD***
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post #9 of 29 Old 09-29-2021, 11:52 AM Thread Starter
giacomom
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Thank you Timo_90xj
that you know there are special drill bits to drill these screws ?

I have drilled a little but now it does not pierce anymore, I have already broken 4/5 drill bits ....


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post #10 of 29 Old 09-29-2021, 12:26 PM
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Quote:
Originally Posted by giacomom View Post
Thank you Timo_90xj
that you know there are special drill bits to drill these screws ?

I have drilled a little but now it does not pierce anymore, I have already broken 4/5 drill bits ...
I would honestly take the cylinder head to a machine shop at that point. You could do the job in a home garage with a drill press and high quality HSS-Co drill bits from underneath, but you'd need to be VERY precise to drill right at the center of the bolt. Might need a helicoil anyway, depending on how it goes.

When I pulled the intake manifold years ago and had the exact same four corner bolts snap, I ended up buying Edelbrock Performer RPM aluminum heads and sold the original heads for 100€.

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1990 XJ Limited (4-door), 4.0 I6, AW4, NP242, ***rolled and totalled @ 165k miles***

***Under construction***
1990 XJ (4-door), 4.0 I6, AW4, NP242, PBR 42" tires, Unimog 404 portal axles, 110" WB, full cage + uniframe completely rebuilt, front 3-link + panhard / double triangulated 4-link rear,... ***SOLD***
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post #11 of 29 Old 09-29-2021, 09:19 PM
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Quote:
Originally Posted by giacomom View Post
Thank you Timo_90xj
that you know there are special drill bits to drill these screws ?

I have drilled a little but now it does not pierce anymore, I have already broken 4/5 drill bits ....


Giacomo
You probably inadvertently burnished the inside of the bolt and hardened it. That happens on the better grades of bolt. No idea what grade the intake bolts are but IMS they are torque to yield so probably decent. If you have the bit RPM wrong or the pressure wrong the bit stops cutting and just heats up the bolt and hardens the steel. If the bolts are grade 8 they would already be near the limit or what HSS bits can handle without damage to the bit anyway. You could try using a carbide bit. That would make the cut. But if you break a carbide bit and the broken part gets jammed in there, the machine shop is going to charge you more. Getting carbide out usually requires diamonds or and EDM machine.
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post #12 of 29 Old 09-29-2021, 11:59 PM Thread Starter
giacomom
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Quote:
Originally Posted by zjosh93 View Post
You probably inadvertently burnished the inside of the bolt and hardened it. That happens on the better grades of bolt. No idea what grade the intake bolts are but IMS they are torque to yield so probably decent. If you have the bit RPM wrong or the pressure wrong the bit stops cutting and just heats up the bolt and hardens the steel. If the bolts are grade 8 they would already be near the limit or what HSS bits can handle without damage to the bit anyway. You could try using a carbide bit. That would make the cut. But if you break a carbide bit and the broken part gets jammed in there, the machine shop is going to charge you more. Getting carbide out usually requires diamonds or and EDM machine.

Most likely this is what happened, burnished the inside of the bolt and hardened it.....
what is a carbide bit ?
I used bits HSS or Co
thank you


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post #13 of 29 Old 09-30-2021, 07:39 AM
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Carbide is the next step up from cobalt. HSS->cobalt->carbide. Tungsten carbide. You can get them in regular twist drill configuration, but beware that they are very brittle. It takes a very steady hand to use them in a hand drill without breaking. They also sell bits for hardened steel that are configured like masonry bits with just the tip carbide but a steel shaft to reduce breakage. Typically used by locksmiths who need to drill hardened steel with a hand drill. They are a little pricey.

https://www.mcmaster.com/carbide-tip...ardened-steel/

I'm surprised that the cobalt bit you tried didn't cut it though.
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post #14 of 29 Old 09-30-2021, 09:45 AM Thread Starter
giacomom
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Quote:
Originally Posted by zjosh93 View Post
Carbide is the next step up from cobalt. HSS->cobalt->carbide. Tungsten carbide. You can get them in regular twist drill configuration, but beware that they are very brittle. It takes a very steady hand to use them in a hand drill without breaking. They also sell bits for hardened steel that are configured like masonry bits with just the tip carbide but a steel shaft to reduce breakage. Typically used by locksmiths who need to drill hardened steel with a hand drill. They are a little pricey.

https://www.mcmaster.com/carbide-tip...ardened-steel/

I'm surprised that the cobalt bit you tried didn't cut it though.

The bits for hardened steel that are configured like masonry bits could it be like these ?
545701 SDX Fischer , with the widia tip ?
thank you


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post #15 of 29 Old 09-30-2021, 01:06 PM
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There are some companies now selling "universal" bits with tips like masonry bits but sharpened to cut metal. From what I've seen (no firsthand experience) they aren't that great. I was thinking about ones like these:
https://www.amazon.com/Carbide-Tippe.../dp/B0837QG55Z

Those are designed to cut steel.

Masonry bits are not sharpened to cut metal. They will not work.
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