Missing exhaust manifold bolt HELP!

Hi everyone thanks for reading,
Somehow the magical ferry that makes bolts disapeer has worked its magic on my 95 4.0 XJ. The bottom back bolt (bottom bolt closest to the driver) on my exhaust manifold has popped out some how. I am wondering what size bolt I need, and if it is a custom bolt where can I get it. THANKS SO MUCH!

It should be 3/8"-16 x 1.25". If possible, it should be replaced with brass or bronze (first choice,) stainless steel (second choice,) or SAE Grade 5 (third choice.)

Do NOT use SAE Grade 8 - they're too sensitive to the heat involved, and you'll lose strength in the screw quickly...

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Hey thanks alot man, im about to take my 95 xj with 150K miles from mia fl to lansing michigan next week and might make the trip a few times a year so i need it running really sound.

ktwalker01 said:

Hi everyone thanks for reading,
Somehow the magical ferry that makes bolts disapeer has worked its magic on my 95 4.0 XJ. The bottom back bolt (bottom bolt closest to the driver) on my exhaust manifold has popped out some how. I am wondering what size bolt I need, and if it is a custom bolt where can I get it. THANKS SO MUCH!

Click to expand...

You sure it didn't snap off? That's a stud with a nut on it and the rear one is prone to fail.

Tom

ratherbcamping said:

You sure it didn't snap off? That's a stud with a nut on it and the rear one is prone to fail.

Tom

Click to expand...

x2 double check it didnt break off.

Thanks for the input alot,
It is a stud, DOH!... I got the new bolt and washer at homedepot and when I went to screw it in, it didnt wanna do to much in the hole.. lol. No idea how it woulda snapped... The manifold is gibson cermaic headers which i got last year around this same time. I would imagine this is a heck of a problem to fix. The engine you can hear leak when its cold after starting but once it heats up everything expands so it seals. (I hope so cause it sounds that way) Anyone know what kind of a job it will be fixing this? I would imagine over time this is gonna reak havoc on my gasket. Please let me know because im soon to be putting easily 20,000 miles on her in the next 6 months!

It's a headache...

Before you get started - I highly suggest you turn the engine by hand until both valves for that cylinder are closed (I'm assuming you're talking about the rearmost screw/stud, no?) and then stuff the ports with clean rags to keep metal bits out. No sense taking chances...

First, heat the screw (using a pencil torch, if you can get one) to, maybe, a dull red and touch a candle or a block of paraffin wax to it - the wax will melt and "wick into" the threads, which should help free it up.

Then, get a left-hand drill bit (if you can) and centre punch the screw and start drilling. If you're lucky, the left-hand drill will "bite" into the screw and remove it for you.

If not, then either a left-hand tap or a screw extractor may be used - but be very careful you don't break either one! They're harder than most drill bits, and you're boned if you break it.

Once you've got the screw out, you can either replace it with another screw (notes in previous post) or get a stick of 3/8"-16 brass threaded rod and cut a stud out of that (cut to about 2 to 2-1/4 inches long, and dress with a file.)

Why brass? To keep this from happening again. Trust me, it won't. I've been using brass and bronze for exhaust hardware for about 25 years now...

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You said it right seems like a headache.
I looked at it really hard earlier when I realized what it was a stud, because I caught reference to the front bottom one. This trick will work for getting out the stud? And I would imagine this will require me taking off the intake and exhaust manifold to be able to get in there and do this.

ktwalker01 said:

You said it right seems like a headache.
I looked at it really hard earlier when I realized what it was a stud, because I caught reference to the front bottom one. This trick will work for getting out the stud? And I would imagine this will require me taking off the intake and exhaust manifold to be able to get in there and do this.

Click to expand...

Yep - that's about the size of it. You're not going to have fun doing this...

While you're about it (and since you have the manifolds off anyhow,) I'd also see about replace the other two studs with brass - the forward end, and the top centre. Cheap insurance...

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Thanks alot for the help. I remember how much of a job it was installing those friggin headers cause of how little space there was and everything how was so aged together. I hope i'll be able to do this one with in a month.. One thing id like to know is right now I know I dont have the time for all that work because I have finals this week and moving to michigan thursday and Im down here in Miami Florida, will this do a number on my gasket? After the engine heats up I dont smell or hear any trace of a leak.

Make sure the other screws around in (especially the two closest!) are torque properly, and that will help.

Also, assume that it's going to cook your gasket - I wouldn't reuse a header gasket that had been run even once anyhow - but I'm just cranky that way.

When you redo the job, since you're going to be tearing it town, order a batch of silicon bronze screws from Fastenal, and your local hardware store will probably have 3/8"-16 brass threaded rod in one-foot lengths (which is already too much - you'll only need about half of it.) Replace both end studs and the top centre one.

Why brass and bronze? Because steel, as you probably know from experience, will gall on steel and iron in the presence of heat. Brass and bronze will not.

Also, steel will get weaker by (very!) small increments with each heat cycle, while brass won't. That's why I've been using it for so many years... Might as well replace the stud nuts at the collector while you're about it - they're probably 3/8"-16 as well. Please let me know if they are not.

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Thanks a million for your help. Your personal message is true for sure, Dangerously Over-educated. Ill double check the torque on all the bolts and go from there. Hopefully i'll get this mess repaired soon.. When ever i have the time. Luckly in Michigan my uncle is a psycho car dude, his home garage has a paint booth every tool imaginable, a lift etc. So i'm sure with your tips me and him can get this done.

ktwalker01 said:

Thanks a million for your help. Your personal message is true for sure, Dangerously Over-educated. Ill double check the torque on all the bolts and go from there. Hopefully i'll get this mess repaired soon.. When ever i have the time. Luckly in Michigan my uncle is a psycho car dude, his home garage has a paint booth every tool imaginable, a lift etc. So i'm sure with your tips me and him can get this done.

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Thanks, and you're welcome. I try to put something funny up all over - after all, humour is a test of truth. If it's funny, it's probably true (you can't make some of this stuff up...)

Besides, "Weird, crafty, and marginally sane" didn't fit...

If you search up my posts, I've given some detailed writeups and a few hints that should help you. Do some digging - it's there. I'll do writeups for my website Tech section later (although there's probably stuff there now you'll find useful...)

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