924Board.org

[emoore924]

This might be manifold gasket, but it could be head gasket too. Did you do a compression check? Make sure you do your diagnostics or you could "fix" the wrong problem..

...and if you take the head off, you must replace the head gasket. Last time I checked, the head gasket set was about $130US for the turbo (preferred even for the NA) or $90 for the stock NA, sans shipping to wherever you are...

[gohim]

I suggest that you do a little more investigation before commencing a teardown.

924 exhaust manifolds are very prone to cracking. Especially if the engine has been run lean (too much ignition timing advance, or not enough fuel in the mixture) or has been overheated. From what I have seen the cracks are usually on the bottom, and not visable if you are just looking down from the top. You need to lift the car up and do a close inspection of the exhaust manifold from the bottom with a light and a mirror.

924s also have a tendency to strip out and lost the exhaust manifold mounting studs. Have you checked to make sure that yours are all there, and properly torqued?

This brings us to the next point. Do you have a couple of torque wrenches with the properly torque ratings? I say a couple because the most accurate reading portion of a torque wrench's range is above 50% of rated capacity, at about 75-80% of rated capacity.

To use the torque wrench properly, you need the correct torque ratings for the parts you are fastening together. DO NOT USE THE HAYNES MANUAL FOR TORQUE SPECS. There are many what would be horrible typos/errors in there. You need to buy a copy of the Porsche Factory SPEC book. You will find all of the critical specs you will need to machine/rebuild the engine in there.

When you tightened up the spark plugs, did you use a torque wrench set the specified torque? Maybe you under torqued the plugs, and they could be suffering blowby because of undertightening. Over maybe you overtightened them, and partially stripped the spark plug hole threads in the cylinder head.

If you do get all the way to replacing the exhaust manifold studs, DO NOT BOTTOM THE STUDS OUT IN THE HOLES. Studs are not designed to bottom out, and doing so may infact damage the threads in the holes.

[tj924]

Checked the top studs & nuts for the exhaust manifold & it would appear that 3 of the 4 nuts are missing (looks like the studs are still there, sticking out maybe 1cm from the manifold) & the 4th stud has worked it's way out with the nut still attached & is stuck where it is by the heat shield (ie when I take off the heat shield the stud & nut will fall out). I've checked the bottom as much as I could with what little time I had & found the nut still in #1. Couldn't see the rest of them but will have a better look next weekend.

So, next weekend I'll check the bottom of the manifold for any signs of cracking & to see if any of the nuts have come off there as well. I think the plan from there will be to put it on stands, purchase the gaskets & a set of suitable stainless steel bolts (will still need 2 stud & nut combinations for the bottom according to Ozzie as he was unable to get bolts in there), then start dismantling. If it turns out (god forbid) any of the studs have snapped off in the head, it'll be "off with her head" & off to a machine shop to have the studs removed properly.

I'll also see what I can do re getting a compression test, but she's running strong with no oil in coolant or vice versa at the moment.
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TJ
Silver '82 924 NA 5-Speed Manual

[tj924]

The PET indicates the studs & nuts on the manifold are all M8. What is the thread pitch? I plan on checking out the local nut & bolt specialists to see if they can supply stainless steel. I think bolts would be the way to go unless they won't fit in some places (as indicated by Ozzie).

Would it help to replace the washers with spring washers to stop the studs &/or bolts from backing out of the head? How else can you prevent the studs from backing out of the head?
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TJ
Silver '82 924 NA 5-Speed Manual

[Ozzie]

I use the double nut method to put the studs in tight.
ie. put 2 nuts on the stud and lock em together. use it like a bolt until tight.
loosen the nuts.

The bottom ones use studs. Yous can use either bolts or studs on the top.
For the nuts I used a special nut which is hard to describe.
It sort of has a washer built into it or flared out at the bottom. Like a building/roofing screw.
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Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

[leadfoot]

I use loctight to keep the studs in place, wurth sell the studs and the special copper nuts... studs are M8 , pitch = 1.25
Leadfoot
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1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...