Topic: MIssing exhaust manifold stud

[jfrabat]

So, I was poking around the engine trying to figure out why it would turn, but not run (turned out ot be a bad cam sensor; see other post), and I noticed that the reason for my Jeep sounding odd (and perhaps the reason my idle is typically on the high side) is that the exhaust manifold is missing a nut (actually, there is nothing there; just the hole on the manifold).

I imagine this means I am currently running rich (I figure some clean air is making it into the exhaust, so the O2 sensor is picking up more O2 than there really is, and is thus adding more fuel to the mixture), which is probably causing my mpg to drop (not that the Jeep is a DD now, but still, if I am to drive it to Costa Rica - a 14 hour drive! - range will be a factor!). 

The stud missing is number 6 from the char (taken from the FSM):



(of course, it HAD to be the hardest one to reach!)

My question, then, is what is the correct way to fix this? 

Felipe

[Jeffy]

Remove the exhaust manifold and hope and pray you get get the rest of the stud out without too much trouble.  This has been covered several times since it's very common.  There's even a thread in the FAQ with the part number for the new stud.

[jfrabat]

Remove the exhaust manifold and hope and pray you get get the rest of the stud out without too much trouble.  This has been covered several times since it's very common.  There's even a thread in the FAQ with the part number for the new stud.

I was kind of hoping to avoid having to take out the manifold (especially since the Jeep now resides in my parents house, and my mom kind of freaks out every time I work on the Jeep!)...  Oh well...  I'll take a look at the FAQ.  Thanks!

[Jeffy]

I was kind of hoping to avoid having to take out the manifold (especially since the Jeep now resides in my parents house, and my mom kind of freaks out every time I work on the Jeep!)...  Oh well...  I'll take a look at the FAQ.  Thanks!

Yeah, it's pretty extensive work but it's not too hard if you can get the rest of the stud out.  The good thing is that the head is what holds the threads in.  The bad is that age and rust can lock the thread in place.  If you're lucky you can unscrew it with a hammer and punch.  Getting a drill down there can be a problem but a reverse drill bit or something like a screw out(not an EZ-Out) would help.  Soak the hole in PB Blaster or some other type of penetrating oil for a day.

[sharpxmen]

x2 on the penetrating oil

i had the exact same stud broken and it's a PITA in the very sense to take it out. if it's missing you're lucky, if it's broken you're in for a treat. I could not unscrew it, i drilled holes starting from a small size bit and try to use 2 different sizes of screw extractors - i eventually end up drilling almost all of it and chasing the thread with a tap - once i got it moving i was able to take out the threads with a needle nose plier (caught one end and unscrew it all the way out)

you won't run rich, i can vouch for that (i had it like this since i bought it and had the AFR gauge for about 4 years, never seen it on the rich side in closed loop, open loop doesn't matter anyway) - there's positive pressure there so the most it can happen is to lose some exhaust gasses aroud the gasket in that spot (which was what i experienced and sounded like a diesel in the morning for about 5 min)

[jfrabat]

So what is the worse that can happen if I leave it without the stud?  I mean, other than noise...  It's run like that for at least 3 years, but now it will be getting dirty...  Don't know if this can end up causing issues when crossing a river or such.

[sharpxmen]

So what is the worse that can happen if I leave it without the stud?  I mean, other than noise...  It's run like that for at least 3 years, but now it will be getting dirty...  Don't know if this can end up causing issues when crossing a river or such.

if water gets there that stud will be the least of your worries (the distributor and coil is lower than the cyl head), water won't make it in thru there but if you stall will come thru the tailpipe, cat and up the downpipe rather