Replacing Exhaust Manifold - "Melted" Head @ Gasket Surface

[bmrisko]

I decided I would replace my pass. side exhaust manifold in holes of fixing an exhaust leak that has been prevalent for a while. The first 7 nuts came off easy, so I was feeling pretty good until I got to the 8th nut (bottom, closest to the firewall). It was backing off way too easily and then fell off with the stud broken below the surface.

It is not one that can easily be drilled out, but I figure I can try building it up with my welder and then welding a nut on it to back it out. However, my other issue is the gasket mating surface on the head around this stud hole appears to be eaten away some. Any idea what would have caused this? Not sure if I get the stud out and replace the gasket and manifold that I am going to due much good due to the area around the stud that appears to be worn away.

 

[bmrisko]

False alarm, got everything cleaned up and the surface is good...just a ton of built up crud around where the leak was.

I got a guy coming later this week who is a mobile welder and specializes in removing snapped bolts in heads, especially ones below the surface.

Wish I could find a good way to get the O2 sensor out to replace it, but it looks like it is going to involve dropping the cats. I'm half tempted to replace the starter while I've got the manifold out since it has 150k+ miles on it.

 

[LEOL]

glad you have it worked out. follow ups are always appreciated!! as for the o2 sensor.... this is an expedition youre working on correct?? The bank 1 downstream is a little fussy to get at because of the heatshield... but still definetly doable, especially if you have an O2 sensor socket/tool. the other 3 sensors are fairly easy to get at even with it on the ground. unless you are just to big to fit under the vehicle and move your arms around... im a smaller guy so i can imagine thats actually a common problem. lol

 

[bmrisko]

Yes, it is a '98 5.4L Expedition. The O2 sensor I'm having trouble with is the pass side upstream (closest to the engine). Not sure which bank that is, I believe Bank 1. I figured having the manifold out would give me access, but it is really tight in there. I've got an array of o2 sockets, but can't really get in there to get a wrench or ratchet on it b/c of the dipstick tube. The other 3 weren't too bad...I'll try from underneath in the morning.

 

[LEOL]

hmm. its been a long minute since ive looked up a 98's skirt but gen2 expy's are a pretty clear shot to the pass/upper o2 sensor from underneath the starter is the big obstruction if i recall. anyway.... extensions and swivels is all i can say. lol.

 

[bmrisko]

Stripped the o2 sensor nut, so I gotta pull the cats. I tried a torch, PB Blaster, CRC Freeze-off, various o2 sockets, a 22mm wrench, getting it from underneath and from the wheel-well. I went ahead and ordered a Walker direct replacement y-pipe & cats for the pass side. At almost 20 yrs old and 150k+ miles, the cats would eventually need replacing anyways. This has been one heck of a little project. At least the truck is a 3rd vehicle and I can work on it when I feel like it...

 

[LEOL]

sorry to hear its being a P.i.t.a. if an engine never has any underlying problems, then "in theory" Cat's actually shouldnt really "go bad" in most cases... BUT though i have seen some... a vehicle with 100's of 1000's of miles on it and Never have any sort of issue or poor running condition is pretty much a unicorn.... so yeah... cats on a 20 yr old vehicle are likely to need replaced at some point.

Anyway, i feel ya... i have to try to get my bank 1 sensor out to do a flow test cuz i suspect the cats may have a very slight restriction due to past underlying issues... and that B1 sensor isnt wanting to budge.... at all. So, here i go. lol.

 

[bmrisko]

Good luck, that sensor has gotten the best of me. 20 yrs of rust doesn't help, especially with the limited amount of space up there...

I've had cats just randomly go bad and start rattling in the past on other vehicles, but there didn't seem to be a rhyme or reason and I agree that it is rare. I hate spending money to replace parts that aren't broke, but at this point it seems like the easiest option as I'm likely going to have to cut the cats & y-pipe out anyways due to rusted fittings.