924Board.org

kaffine · Joined: 13 Jun 2003 Posts: 644 Location: Las Vegas

Well I finally got to drive my 24 to work. Unfortantly I now have 2 problems that need to be fixed before I drive it again. The shift linkage and an exhaust leak.

The exhaust leak is the bolts on the exhaust manifold have backed out and 4 are missing along with one of the gaskets. The ones that are missing are for the #1 and #4 cylinders.

What size of bolt will I need to replace to missing ones? Are there any retention straps made to go over the bolt heads to keep them from backing off? I know on Dodge diesels they have a tsb to install straps on the bolts for the #1 and #6 cylinders for the same problem unfourtantly they have much larger bolts and wont fit on the 24.
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80 924
80 931

The best desciption of an atom boils down to something unknown is doing we don't know what.
Sir Arthur Eddington

Paul · Posted: Tue Sep 02, 2003 9:26 am Post subject:

for a 80 NA

M8 x 18 part # N 044 511 1

Rob O · Joined: 26 Nov 2002 Posts: 86 Location: Oak Ridge, NJ

The exhaust manifold to head studs on my #1 cylinder have started to loosen. I am thinking I should replace the studs, nuts and the gasket on this cylinder before I drive the car any further. Can I just back both studs out and slide the new gasket in then insert new studs?

Can I just replace the studs with bolts? Any downside to using bolts? This seems cheaper/easier.

If I should use studs, I want to make sure they are replaced properly. I read in a different post discussing replacement of the head to manifold studs that you do not screw the studs in all the way, only far enough to make them even with the others. Is that correct?

Thanks,

Rob
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'81 Weissach Ed. (gettin' better)

Rob O · Joined: 26 Nov 2002 Posts: 86 Location: Oak Ridge, NJ

Well, I have confirmed that you cannot just remove the studs and slide the new exhaust manifold gasket in on the #1 cylinder. There is not enough room.

Now I am unable to remove the manifold from the head.

I removed all eight of the nuts holding the manifold to the head. Four of the studs backed out with the nuts. I thought the manifold would just wiggle down off of the four remaining studs so I could clean and reinstall eveything with new gaskets but the manifold will not come off. I slipped a crowbar in between the head and the manifold and pulled with moderate force but the manifold only rocked slightly. It appears to be frozen to one of the studs on the bottom row.

Any suggestions for separating the manifold from the head? I have been dowsing the offending stud with pblaster for over a week. I tried my propane torch and I tried to double nut the stud and back it out, all with no luck. Any insight is greatly appreciated. Weather is warming up and I want to put the car back on the road.

Rob
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'81 Weissach Ed. (gettin' better)

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

FWIW, when I was doing my exhaust/turbo project, I bit the bullet and bought a Snap-on stud tool, with the inserts required for the job. It was a bit expensive, but worth it IMO (as it saved trips to the machine shop for extraction of broken studs).

As for material, I would strongly recommend the Porsche studs and nuts. The failure you are describing was a 924 problem that I believe Porsche corrected by changing the stud material.

And last, studs should be inserted as far as they can go without bottoming or shouldering.

You disconnected the down pipe, right? It seems odd that the manifold could stick on a stud. . .oh, and don't pry against the gasket sealing surface.

Good luck.

rasta
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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

Ozzie · Posted: Thu Mar 15, 2007 7:39 am Post subject:

I have had the exhaust manifold off, retapped the holes, replaced gaskets and replaced studs and nuts all while the motor was in the car (and RH drive) so the answer is yes, it is possible.
You'll learn patience though.
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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

Benino · Posted: Thu Mar 15, 2007 8:21 am Post subject:

I just recently removed the manifold from my 924. It didn't get stuck on any studs but with still about 1 or 2 mm of the studs sticking into the holes in the manifold, the manifold would hit the wheel well and not come off. Instead of trying to doublenut and remove all of the studs with the manifold in the way, I had a friend pull on the engine from the drivers side to flex it in that direction against the engine mounts. This way I was able to clear the studs without bumping into the wheel well and remove the manifold.

About using bolts instead of studs: This is not a good idea. The head is aluminum, so it would be much easier to strip the threaded holes if you are turning the bolt in the head to achieve the amount of torque you want. Also, not as important, but it is easier to install the gaskets when there are studs because the studs stay in place and hold the gaskets in place as you put the manifold on.
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1980 Porsche 924 N/A USA
1980 Porsche 924 turbo USA
1987 Porsche 944S USA

Rob O · Joined: 26 Nov 2002 Posts: 86 Location: Oak Ridge, NJ

Thanks for all the replies. I had some time this weekend and was able to remove the manifold. I took a length of 2x4, wedged one end against the flange of the manifold where it connects to the downpipe and then hammered on the other end. Manifold popped off the studs after about a minute of whacking away.

Now I have a new question. Looking at the faces of the manifold where it mates with the head, two of the cylinders have some pitting. These are the two cylinders where the gaskets blew out. There is still clean metal all the way around the hole to form a good sealing surface but I am afraid that I will be doing this again soon if I do not replce the manifold or have the sealing surfaces machined smooth again. Has this happened to anyone else? Is there enough material on the cast iron flanges to remove about a 32nd of an inch or will this cause cracking around the flanges when I torque it back on?

Thanks,

Rob
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'81 Weissach Ed. (gettin' better)

Rob O · Joined: 26 Nov 2002 Posts: 86 Location: Oak Ridge, NJ

Just wanted to follow up.

I took the exhaust manifold to a local machine shop and they took 6/1000's off the flanges. Hopefully that does not cause the flanges to crack. The shop charged me $50 - that seemed reasonable.

I replaced six of the eight studs, replaced the gaskets and used copper nuts from Paragon to hold it together.

I had to replace three of the socket head nuts that hold the downpipe to the manifold. Those go for about $45 each so I used regular m10x1.5 stainless steel nuts on three of the studs. They fit with no problem at all.

Car is back together and back on the road. Feels good to drive her again.

Rob
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'81 Weissach Ed. (gettin' better)

leadfoot · Posted: Thu Apr 19, 2007 10:15 am Post subject:

Congrats, FWIW the downpipe nuts are also the same copper ones used for the head studs...
You can get them from Wurth. They also have the copper washers to and studs. A pack of 50 studs was about 25$ from memory.
Never had a problem with the copper nuts coming off. If anything they tend to pull the whole stud out with them.
Leadfoot
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1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...

!tom · Posted: Thu Apr 19, 2007 4:34 pm Post subject:

All other cars I've worked on have had steel nuts on the exhaust manifold and downpipe nuts. And, yes, they do get quite rusty due to the heat, but they can still be removed after many years (I just pulled the exhaust manifold off a 20+ year old car last month when I popped the head off).

Why the copper nuts on the Porsche?
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78 924 NA
5-lug