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Hey guys, I was hoping to get some help in addressing an exhaust leak on my '73 Deville. The car my first project car (I'm 18 and trying to learn wrenching), and I'm already having difficulty. The previous owner said the leak was caused by an exhaust flange gasket. However, I'm wondering if it's caused by a missing bolt. I removed a nut from the bottom screw (in the area shown in the attached pictures). However, I noticed there's no nut or bolt in the top hole. Will a nut and bolt in the top hole be enough to stop the exhaust leak?


Many Thanks,
Jackson
 

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Looks like that pipe connects to the exhaust manifold?

If so, you'll need an exhaust doughnut (glorified gasket) and new bolts/studs.


Tighten each of the bolts from side to side a few turns each when you put it back together. You do not want to totally Titan only one of the bolts to get started. Alternate back and forth turning each Bolt a couple times.

This ensures that the flange tightens evenly.
 

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Discussion Starter #3
Looks like that pipe connects to the exhaust manifold?

If so, you'll need an exhaust doughnut (glorified gasket) and new bolts/studs.


Tighten each of the bolts from side to side a few turns each when you put it back together. You do not want to totally Titan only one of the bolts to get started. Alternate back and forth turning each Bolt a couple times.

This ensures that the flange tightens evenly.
Much appreciated! It does connect to the exhaust manifold like you figured.
 

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Looking at the photos more closely now... looks like the one stud may have broken off? Is the stud/bolt still partially in the hole? We can see one, but is the other there?

Broken exhaust manifold studs can be a bear to remove and replace. If the one that is broken off is flush with the manifold, it will be some fun. By fun I mean, probably quite a bit of drilling to open up the hole. You'll need to heat it with a torch also before attempting extraction of the broken bolt/stud
 

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Discussion Starter #5
Looking at the photos more closely now... looks like the one stud may have broken off? Is the stud/bolt still partially in the hole? We can see one, but is the other there?

Broken exhaust manifold studs can be a bear to remove and replace. If the one that is broken off is flush with the manifold, it will be some fun. By fun I mean, probably quite a bit of drilling to open up the hole. You'll need to heat it with a torch also before attempting extraction of the broken bolt/stud
Thankfully, it's not broken off. It is missing, but it does not appear to be trapped in the hole. Hopefully I should be able to touch up the area with some rust remover and just put a new stud in.
 

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I've been doing some work on my '76 Fleetwood and pulled my Y pipe so I could drop the oil pan. I can give you the measurements/take any photos if you need them. There should definitely be something there and that would probably be a likely cause of an exhaust leak. While you're down there you'll want to check for any other pinhole exhaust leaks too though. I've got a CA car, but over the years there were a bunch of small leaks here and there so I had to have all of the exhaust from the catalytic converter back replaced a few years back.

How I generally test for exhaust leaks is I take the output from my shop vac and duct tape it to the tail pipe with the car off and cool. Then I just run it and feel around the exhaust to find where I feel a slight breeze of escaping air. I don't like running the shop vac for too long because the lack of airflow could overheat it.
 

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Discussion Starter #7
I've been doing some work on my '76 Fleetwood and pulled my Y pipe so I could drop the oil pan. I can give you the measurements/take any photos if you need them. There should definitely be something there and that would probably be a likely cause of an exhaust leak. While you're down there you'll want to check for any other pinhole exhaust leaks too though. I've got a CA car, but over the years there were a bunch of small leaks here and there so I had to have all of the exhaust from the catalytic converter back replaced a few years back.

How I generally test for exhaust leaks is I take the output from my shop vac and duct tape it to the tail pipe with the car off and cool. Then I just run it and feel around the exhaust to find where I feel a slight breeze of escaping air. I don't like running the shop vac for too long because the lack of airflow could overheat it.
Thanks very much. I'll grab my vacuum and give that a go before I get much further. I'm showing my mechanical ignorance in asking this, but would you happen to know the right size exhaust stud for the car? I used a 9/16 socket to undo the nut threaded to it. Is an M10 stud kit, like the one shown at Advanced Auto, going to work?

 

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This is one of those jobs that is routine, and really easy with air tools, and sometimes needs a torch. So, it can be tough with hand tools on your back. To fix it, the y pipe needs to be dropped. It will only cost about ten bucks in parts. Even if you take it in to an exhaust shop, it will be less than an hour.
 

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It's great hearing new wrenchers coming up. But at your age my dad didn't have set of box/opens much less an air compressor or torch. In case you're just starting your tool collection then all the above, plus if this ain't your driver and no airtools, then simply successive rounds in order (patiently) with PB Plaster and a light hammer, then a MAPP gas torch (in case acetylene was presumed) and and invest in a set of deepwell sockets.

Also, I was a dumshit at your age starting out and used whatever boards and bricks were laying around for stands. Don't be that guy.

And while I'm here spending your $$$ you'll wonder how you ever lived without a set of Factory Service Manuals. Whatever you pay for a set you'll always get back when you ditch the car. They also have online access for paid subscription. Cheap, as it saves you 5-15x the cost on your first repair.
 

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Thanks very much. I'll grab my vacuum and give that a go before I get much further. I'm showing my mechanical ignorance in asking this, but would you happen to know the right size exhaust stud for the car? I used a 9/16 socket to undo the nut threaded to it. Is an M10 stud kit, like the one shown at Advanced Auto, going to work?

No worries been there and done that. You've got to start somewhere right? I got my '76 Fleetwood back when I was 17 and knew nothing about how to work on it. Just gradually picked up tools and knowledge over the years.

I measured the stud on mine and it's a 3/8" - 24 thread, about 1.5" long for the part that protrudes past the nut. The M10 won't work since these cars are SAE and not metric. Good luck!

I also totally support the factory shop manuals. Those things are godsends and I've got a copy for all my cars.
 

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No worries been there and done that. You've got to start somewhere right? I got my '76 Fleetwood back when I was 17 and knew nothing about how to work on it. Just gradually picked up tools and knowledge over the years.

I measured the stud on mine and it's a 3/8" - 24 thread, about 1.5" long for the part that protrudes past the nut. The M10 won't work since these cars are SAE and not metric. Good luck!

I also totally support the factory shop manuals. Those things are godsends and I've got a copy for all my cars.
I greatly appreciate it! There's a small hardware & auto-parts shop near me that has a stud very close to that in stock. I look forwards to giving it another go in the coming days. I also have a 1973 Shop Manual on the way, as well as a Haynes repair manual. I just got restless and decided to start doing work on the car before they came in. Thanks again for the help!
 

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It's great hearing new wrenchers coming up. But at your age my dad didn't have set of box/opens much less an air compressor or torch. In case you're just starting your tool collection then all the above, plus if this ain't your driver and no airtools, then simply successive rounds in order (patiently) with PB Plaster and a light hammer, then a MAPP gas torch (in case acetylene was presumed) and and invest in a set of deepwell sockets.

Also, I was a dumshit at your age starting out and used whatever boards and bricks were laying around for stands. Don't be that guy.

And while I'm here spending your $$$ you'll wonder how you ever lived without a set of Factory Service Manuals. Whatever you pay for a set you'll always get back when you ditch the car. They also have online access for paid subscription. Cheap, as it saves you 5-15x the cost on your first repair.
Well, I got the stands thing under control; I'm using a nice set of ramps. Although, I don't have much in the way of tools (except for a large ratchet set.) It looks like I'm going to need an air compressor down the road, so I might as well bite the bullet for that now. I appreciate the advice re: the shop manual. I have a 1973 shop manual and a Haynes repair guide coming in a week or so. Truth be told, I didn't expect an exhaust leak to take more than a ratchet and screwdriver! it seems as I have a lot to learn (y)
 

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That's a 3/8" stud missing.
I would have guesed 3/8"-16 (course) not 3/8"-24 (fine).
But I don't have one in front of me.
In a pinch a bolt would work in place of a nut.

IDK if your stud is broken off or missing.
You really need to get the front pipe out of the way to work on it.

If you got a broken stud with something to grab you're in luck.
Soak & let sit several times with rust penitrating oil. Use something better then WD-40.
Get a small take of MAP gas & toruch head at the hardware store.
Also get some Vice Grips with curved jaws medium & small.
They also make stud removers for this.

Heat the manifold best you can till it's glowing in the stud area.
Let it cool. More penitrating oil. The thermal cycling helps lossen.
Heat again and clap the stud remover or Vise-Grips on and try an lossen.
Don't try too turn too hard. The stud will just break.

Bolt removal is really a skill learned over lots of frustration.
They may even have videos how to remove exhaust manifold bolts / studs.

If possible it's best to run a tap in the threads with oil to clean out.
Don't twist too hard or sideways or the tap will snap off.

Put some anti-sieze on the new hardware.
Get quality hardware if you can, not just the bulk $0.07 nut.
They sell stud & nut kits.
Replace the other nut while you have it off.

If it seems to much don't be afraid to take it to a mechanics shop / exhaust shop to be reapired.
Problem with this is it could snowball. Where the manifold needs to be removed to be repaired or replaced.
Then bolts break off in the cylinder head. Then the head needs to be pulled.
 

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Those studs were 3/8" x fine thread where they stick out through the Y pipe flange and 3/8" course where they go into the manifold.

There is no doughnut or gasket of any kind on this series of engine exhaust flanges.

A good trick is to replace the fine thread nuts with brass nuts so they remain serviceable.
 

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Discussion Starter #15
Those studs were 3/8" x fine thread where they stick out through the Y pipe flange and 3/8" course where they go into the manifold.

There is no doughnut or gasket of any kind on this series of engine exhaust flanges.

A good trick is to replace the fine thread nuts with brass nuts so they remain serviceable.
Interesting that there's no gasket at all. I've actually replaced the missing stud, but have been unable to re-thread a nut onto the remaining stud. The threads are so messed up that nothing will twist on. I very well might have to remove the stud and replace that one as well.
 

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A new nut could help.
Make sure you get the right number of threads on the new nut.
They have thread chasers, thread files, or dies that could be used to clean up the old threads.
But if the studs missing too much metal from rust it work very well anyways & should be replaced.
 

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......... I very well might have to remove the stud and replace that one as well.
Gratifying to hear a young person even considering prophylactic maintenance and future return on effort. And there's no better time for clear access than with it all disconnected.
 

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A good trick is to replace the fine thread nuts with brass nuts so they remain serviceable.
This ^^^
When I replaced my stock exhaust manifolds I took the same advice and purchased brass nuts, but went one step further with stainless studs and lock washers.
 

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This ^^^
When I replaced my stock exhaust manifolds I took the same advice and purchased brass nuts, but went one step further with stainless studs and lock washers.
I've been using stainless studs and brass nuts. All the studs have been replaced except the one I haven't yet managed to free.

Maybe a die or a thread restorer is all you need.
I think I'm going to try this next. I've already tried a stud remover ratchet attachment, but had no luck. I'm hoping I can avoid dishing out money for pneumatic tools, though I might have to. I'll need them later on down the line, anyways.
 
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