Leaking exhaust-manifold-to-exhaust-pipe gasket

[AlaskaFestivaGuy]

1993 Festiva, manual, one of the 8 members of my Seattle fleet, with only 102K miles.

I've been smelling "exhaust smell" in the car for a while, and recently saw smoke coming out the front grille while at a stoplight.

I tracked it down visually to what appeared to be a leaky exhaust manifold to exhaust pipe gasket. This is the 3-bolt-hole gasket where the vertical section of the exhaust pipe attaches to the exhaust manifold. It's either that, or there's a crack in one of the parts through which exhaust gas was escaping. But it sure looked like it was coming out at the gasket, right next to the "tab" that sticks out (which I presume is so a mechanic can look at the joint and be certain that a gasket is in there).

I've removed the exhaust manifold from the car.

The subject gasket appears, strangely, to be 2 layers of material tack-welded to each other. Is this how it came from the factory, i.e. the best solution? The exhaust-manifold-to-block gaskets appears to be 2 layers also. I've ordered new of both gaskets from Napa. When installing, should I use any sort of paste-like exhaust sealant? If so, is there a brand name? The NAPA guy said no sealant is required.

BTW, I did a search before posting, and my Haynes books is 1500 miles away.

I'm surprised that a metal gasket like this leaked. I checked, and all three 14mm nuts were tight before I disassembled. Any thoughts? The car has only 102K on it. Any recommended torque setting for both this connection and also attaching manifold back to the block?

[Pu241]

I've had both OEM 3 hole manifold to down pipe and manifold to block gaskets burn/corrode through. But mine had many more miles than yours.
I'll see if I can find the torque settings.
I've never used anything but the gaskets when installing them.
Obviously, after a good thorough cleaning.
Doesn't mean there not something that might help the seal.

[TominMO]

I've had both OEM 3 hole manifold to down pipe and manifold to block gaskets burn/corrode through. But mine had many more miles than yours.
I'll see if I can find the torque settings.
I've never used anything but the gaskets when installing them.
Obviously, after a good thorough deaning.
Doesn't mean there not something that might help the seal.

According to Haynes page 2A-2, 23 to 34 ft lbs for bolts fastening downpipe to manifold.

John, what is a deaning? What sort of things need to be deaned? Is this some secret process only Dean knew of?

[Pu241]

A deaning is one step better than a cleaning.

No, really it's a contraction of cleaning, note by removing that space between the "c" and the "l" you get "d", and thus deaning!

[TominMO]

A deaning is one step better than a cleaning.

No, really it's a contraction of cleaning, note by removing that space between the "c" and the "l" you get "d", and thus deaning!

I thought that's what you were doing, but didn't want to give you credit if you weren't!

That must have saved you about 1/10 second of typing....except you had to use another post to explain it!

[eurotiva]

I use the spray on copper gasket (permatex aerosol). goes on super thin and seals the imperfections. My cars require a good seal for the turbo to work right.

[Festiva Time]

Install the gasket dry. Did you check the exhaust manifold for cracks? Cast iron tend to crack. The crack maybe hard too see. You probably just needed a new gasket.

[AlaskaFestivaGuy]

Now that I have it out of the car, I will inspect the exhaust manifold thoroughly for cracks. I'm wondering if I should even remove the "downpipe" part from the car (I think it's only held on by the support bracked and the two nuts on the front end of the catalytic converter) to inspect it also, though it appears to be steel, not cast iron.

I think I need to be careful here to be sure exhaust gasses aren't getting into the inside of the car. Carbon monoxide is deadly!

[Pu241]

Yeah, if you've already had the gaskets burn through, I'd check the flange area of the connection the down pipe makes to the cat. converter. These tend to break loose from their welds and you end-up with an exhaust leak. Which then requires you to pull the down pipe and have it welded up. So you'd be ahead of the game doing it now.

[AlaskaFestivaGuy]

Here (photos) is what Napa came up with. Not even what I think of as real gasket material.
The manifold-to-block gasket is paper with some sort of gray paint-like stuff on it.
The manifold-to-pipe gasket is paper with a thin soft metal ring.

Compared to the stamped metal parts that came off, I'm not impressed!

Anybody have any thoughts as to whether or not this stuff will work? I'm tempted to put the metal manifold-to-block gasket (which I don't think was leaking) back on, and look for something more robust for the downpipe gasket (the metal one I took off probably was leaking).

[fastivaca]

I'm using the same Felpro manifold gasket with the header I just installed. Haven't had any problems with it.... so far.

[m715]

The only other thing I can think of reading your posts are that your downpipe is actually two wall thicknesses, with the outer wall acting as an insulator. Does your inner pipe have a hole rusted in it, and the exhaust you saw coming out you thought at the gasket surface actually have it coming out where the seam of the pipe is? This could travel up the downpipe to the manifold connection even all the way from the cat connection to escape. Like you said, John, that point, and where the clamp connects to the engine bracket are places they fail.
I have never had one of those steel gaskets fail on any of mine, and some of my downpipes got VERY rusty to the point they rattled before I changed them.

HTH
Michael

[AlaskaFestivaGuy]

m715,

That's an interesting possibility. I haven't removed the downpipe from the CAT yet, but will take it (the downpipe) out Saturday and have a very close look at it. It really is hard to imaging that what appears to be a mint-condition metal gasket is the source of the leak. There's simply no rust in any of my 8 Festies here. Also the volume of "smoke" I saw coming out from that area just seemed to be far greater than what could possibly come from a leaking gasket. Maybe my real problem is indeed back at the CAT.

[AlaskaFestivaGuy]

Source of exhaust leak???

OK, so I got the downpipe off. It has no significant rust, and I can't see any cracks, outside or inside, on either end.

I notice that it has this outer sheetmetal layer, which does NOT completely seal on either end. What's under that layer, one continuous bent pipe? Several pipes, some bent, all welded end-to-end? I don't understand why it's made in such a complicated way.

I took the closeup photo from the angle where I saw the exhaust leaking prior to disassembly.

Short of any other ideas, I see no alternative but to figure out which gaskets to use (probably the original to-block metal one and the new to-downpipe paper one), reassemble everything, and see what I've got. I'll leave the heat shield off so I can examine better what's happeninig.

[AlaskaFestivaGuy]

BTW, I busted off one of the heat shield bolts during disassembly. I drilled out most of it (it's nonstructural, so I can be sloppy here) and am ready to re-tap, but ...

I measured one of the bolts on a gauge at a parts store and determined that it was "M4-1.0." However, I can't find any tap like that. rather only M4-0.70. Did I read the thread gauge wrong? Does anybody know the proper thread for the heat shield bolts? Hopefully, the same size is used elsewhere on Festies so my box of loose hardware should have one.