I recently fixed a broken exhaust manifold bolt on my 96 Roadmaster, which necessarily involved removing and reinstalling the manifold. This sounds simple, but of course it's not. It challenged my rudimentary shade tree mechanic skills, so I offer here a run through with some tips for those who may have to do this sometime and, like me, are not a real mechanic and have not done it before.
Here's the broken bolt as it looked on the car:
As usual, the factory service manual and haynes book were invaluable but rudimentary. I had to figure out lots on my own as I went. Every bolt was an adventure. My broken bolt was on the passenger side, which I believe is the more complicated side to access.
Here's all the tools I used, if that gives you any idea how involved this project is:
Removal (underside):After lifting and jackstanding the car in a way that gives you good access to the exhaust pipe/manifold joint, undoing that joint is the first step. Both the bolts and the nuts have to be removed (15mm regular socket with extension for nuts, 7mm socket with extension for bolts). I applied some penetrating oil awhile ahead (as best I could with awkward access), which hopefully helped. If you are having a good day, they will come out without difficulty. At the very least, a breaker bar will be needed because they will have decades of immobility to overcome, and hopefully not a prohibitive amount of rust (my AZ and TX car is pretty good in that respect). The bolt unscrewed out with the nut on the first one . That's best case scenario. The nut unscrewed off the bolt on the second one and then the bolt screwed out. Not bad. The third is the one that gave me trouble (isn't that always the way?).
The nut came off fine, but the bolt was stubborn and the hex end stripped. Plan B was to undo the pipe from the chassis so the pipe would drop down and the manifold could be removed with the bolt in place. Not too hard, it just was another step. Once the manifold is off the car, the bolt unscrewed easily enough with vice grips.
Also from under the car, you will need to remove the bolt holding the oil dipstick in place and the EGR pipe fitting on the engine side of the manifold near the manifold/exhaust pipe joint. It's only one bolt, but it is really up there in a tight spot. I did it after taking all the manifold bolts out because I didn't realize it was there until the manifold wouldn't come out, so that may have actually made the bolt easier to access. I then had to disconnect the pipe from the intake manifold to be able to move the manifold around enough. Then I was able to think flexible thoughts, get my arm up there and use the closed end of a boxend wrench (13mm IIRC). The wrench would only have a couple inches of travel, so it takes a while to get it out.
Removal (top side):To get the manifold off, you have to remove the alternator. On a wagon with mechanical fan, the tensioner is accessible only from underneath and works best with a 13mm boxend wrench. Removing the manifold bolts is not too bad. They use a 15mm socket. Most work fine with a deep socket, but the frontmost and rearmost end bolts are trickiest (my back end one was the broken one). Manuals said to remove the spark plug wires. I didn't because they didn't seem to be in the way, and I never saw any problem with leaving them on. If you have a functional AIR pump, that piping will obviously have to be undone. Fortunately, I removed the system on mine already (it's not needed to pass emissions).
Parts/preparation:Fortunately, the broken bolt was sticking out from the engine block a good 3/8", so it was very easy to twist it out with vice grips.
I went to a real hardware store and the bolt guy was able to match the bolts exactly with new Grade 8 ones, as well as find some spacers that matched perfectly (the spacer on the broken bolt was gone).
When I was at the pick-a-part yard and looked at lots of GM and other cars, including LO5 5.7's and LS truck engines and I couldn't find one that uses spacers on the bolts. Strange, I wonder why the LT1 uses them? Especially since it doesn't use them on every bolt, just 3 of the 6 on that side of the engine. Two of the bolts are extended ones with extra threading to attach brackets for the alternator. I didn't try to get new ones those. Perhaps I will regret that later.
It was recommended on the forum to take the manifold to an automotive machine shop and have them plane the surface to get it totally flat, in case it had warped out which caused the bolt to break in the first place. I tried, but I had a hard time finding a machine shop in my area. The one I did find didn't have the machine to do that. The proprietor recommended instead to use an old-style particle gasket rather than the thin metal OEM one. This would have more compressibility and if there was a slight imperfection in the manifold, would still make a good seal. I used a gasket set from Oreilly that was listed for an 80's vintage Chevy truck 350. They are separate gaskets for each exhaust port, so I used a high temp gasket maker to hold the gaskets in place on the manifold. I would recommend letting them dry in place for a few hours at least, so they don't tend to fall off like they did when I only let them dry for a half hour. I got a new standard gasket for the manifold/exhaust pipe joint.
I had previously disabled the AIR injection system and removed everything except the main pipe which runs from one side, under the engine and up to the other side. Since I had the manifold off, I cut most of the pipe off so it was not longer in the way. This made putting the manifold back on a bit easier.
Installation (topside part 1):I put the manifold on first. I figured if I put the end bolts in first loosely, it would place the manifold in position to get all the other holes lined up. The first time, I put the front bolt in first, but then I couldn't get the back bolt to line up, so I redid it with the back bolt first. That worked for some reason. I screwed all bolts in, but not quite all the way, so there would be a bit of play in case I needed it to get the exhaust pipe connected.
Installation (underside):I bought a set of new bolts and nuts for the exhaust pipe joint, since the hex head stripped on one of the old ones. (see picture of package above) Unfortunately, they were generic and didn't have a hex head, just threads all the way to the end. I could have made those work, I think, but screwing them in would be much easier with the hex heads. Since it was only stripped in the out direction, I was able to screw it in ok. If I ever have to do this again, I will do like I did before when it wouldn't come out until I removed the manifold.
Next I connected the EGR pipe. This didn't go on any easier than it came off. I had a heck of a time getting in in place. I think I ended up going from the top to push the pipe in place, then screwing the bolt in from the bottom. The experience was a bit of a blur because I tried a bunch of ways until I found one that worked.
The trick part of connecting the exhaust pipe joint was when I put them together, they didn't line up. Pretty damned far from lining up, actually, which was annoying. I was able to overcome this by sticking a phillips head screw driver in the hole closest to the transmission and pushing it to the side until the holes lined up enough to screw the other two in. I put my bad bolt in last in the screwdriver hole, since it was the easiest to access.
Installation (topside part 2):The last step was tightening the manifold bolts all the way, which was the home stretch. This was relatively easy, though getting a torque wrench in position was a bit tricky on a couple of the bolts. I never could get it onto the frontmost bolt. A deep socket was too long and short one too short. Perhaps a medium I didn't have would have worked. I made due with estimating a similar torque by hand.
I haven't done the driver side (and hopefully won't have to), but I imagine it would be somewhat easier. It surely would if for no other reason than there's no EGR pipe.
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Tue Dec 07, 2021 12:52 pm
