FJ62 exhaust manifold leak (1 Viewer)

[martyjayFJ62]

Hi again, the next thing that is becoming a real pain to fix on my 1989 FJ62 is the exhaust manifold, which is leaking like a bastard.
What is the best way to diagnose exactly where the leak is coming from, I was thinking a using a smoke machine to feed smoke into the carby would work, then I should see where smoke comes out of the exhaust manifold?
If I can pinpoint the source of the exhaust leak, what are the best ways to fix it? I already installed a new exhaust manifold gasket and re tightened all the bolts / nuts that hold the manifold onto the engine block, none of these things have made the echaust leak any less loud.
I can feel the hot air blowing onto my hand when I put it up near the rear of the engine block.
Any help is appreciated, cheers.

Images attached of the area where I can hear and feel the leak

 

[mattressking]

The only places an exhaust leak will occur on the manifold is in the following places:

1. Intake/Exhaust Manifold to Head, Gasket. Common warpage point, not sure if as prevalent on carb'd 3F but common on carb'd 2F. Plus material and general design at the head mounting surface is the same, so I assume it is likely. In the picture, it looks as if there is a gap between gasket and exhaust manifold on the rear section, but that could be the picture and dark spots playing tricks.
2. If leak seems to be coming from rear of motor, that most likely eliminates the spring/ring seal between the two manifolds under carb.
3. The easier of the 3, the manifold to down pipe gasket, which happens to exist right below that area you are experiencing a leak.
4. And lastly, the gasket between intake and exhaust manifold which is below carb as well.

An option is to wait until truck is completely cold, go through all the manifold to head bolts and verify they are tight, its a good place to start, same for downpipe nuts.

While this is going on, as a curiosity, how is vacuum at idle? If manifolds are warped and leaking, its likely there is a vac leak as well.

Other notable items...you have what appears to be a few unhooked vac lines...can't see their source but I don't know if that is due to you searching for leaks.

 

[martyjayFJ62]

The only places an exhaust leak will occur on the manifold is in the following places:

1. Intake/Exhaust Manifold to Head, Gasket. Common warpage point, not sure if as prevalent on carb'd 3F but common on carb'd 2F. Plus material and general design at the head mounting surface is the same, so I assume it is likely. In the picture, it looks as if there is a gap between gasket and exhaust manifold on the rear section, but that could be the picture and dark spots playing tricks.
2. If leak seems to be coming from rear of motor, that most likely eliminates the spring/ring seal between the two manifolds under carb.
3. The easier of the 3, the manifold to down pipe gasket, which happens to exist right below that area you are experiencing a leak.
4. And lastly, the gasket between intake and exhaust manifold which is below carb as well.

An option is to wait until truck is completely cold, go through all the manifold to head bolts and verify they are tight, its a good place to start, same for downpipe nuts.

While this is going on, as a curiosity, how is vacuum at idle? If manifolds are warped and leaking, its likely there is a vac leak as well.

Other notable items...you have what appears to be a few unhooked vac lines...can't see their source but I don't know if that is due to you searching for leaks.

I tried the smoke into the air intake method, no good, no smoke leaking through the manifold area.
Next step will be to take off carb and get back into unbolting the manifold, I will try to take the manifold pieces completely off the car and inspect them carefully.
The vacuum hoses are loose because I changed to an after market carb a few months ago, and I honestly have no idea where those hoses should connect now, I am contemplating putting the original carb back into the car.
As for vacuum leaks at idle... I don't know how to check for that, it idles OK at about 700 rpm, if I tweak the carb down to 500rpm it will stall when cold.

If I take it all apart and cannot find an obvious break / hole / crack then should I possibly just double gasket it and use some kind of gasket goop?

Thanks

 

[mattressking]

I tried the smoke into the air intake method, no good, no smoke leaking through the manifold area.
Next step will be to take off carb and get back into unbolting the manifold, I will try to take the manifold pieces completely off the car and inspect them carefully.
The vacuum hoses are loose because I changed to an after market carb a few months ago, and I honestly have no idea where those hoses should connect now, I am contemplating putting the original carb back into the car.
As for vacuum leaks at idle... I don't know how to check for that, it idles OK at about 700 rpm, if I tweak the carb down to 500rpm it will stall when cold.

If I take it all apart and cannot find an obvious break / hole / crack then should I possibly just double gasket it and use some kind of gasket goop?

Thanks

Start with just tightening the manifold hardware, but if you can't completely pinpoint and spraying soapy water, pb or something to see if bubbling occurs. If nuts/bolts are loose, thats a good sign.

The smart method for this is to remove manifold, disassemble completely, clean, reassemble with new gaskets/rings and have a machine shop check the mating surface for flatness once the manifold assembly is torqued together. That should resolve all issues.

You can also take the manifold off as an assembly, place on completely flat/smooth surface, then check for gaps....I forget the tolerances but a search on here would yield an answer, its been covered numerous times.

 

[3_puppies]

generally there will be tell tale signs of an exhaust leak, blackened area . especially with a new gasket.
did you re-torque the manifold after initial install?
do not use 2 gaskets and do not use any goop.

 

[martyjayFJ62]

OK, after working on it today for about 4 hours I think I know where the leak was and hopefully when I re-assemble the manifold, no exhaust leak. But there are a few things I could use help with.
So I did the only thing that made sense and took everything apart, first took off the carb then undid all the bolts on the manifold, the bolts were actually all quote loose, I think I need to use the torque wrench when I re-assemble.
I tried to separate the intake manifold from the exhaust manifold, by undoing the bolts that sit below where the carb sits, but one of the bolts had sheared off with age and never been fixed, so I had to keep intake and exhaust together until I got it off the engine.
Next I crawled under the car and started unbolting the exhaust manifold from the exhaust pipe, 3 bolts hold that on, 2 were fine, the third was sheared with rust as well, had to end up using a dremel to cut it off. I can see why the previous owner was too lazy to fix this issue!
Finally I could get the entire manifold system out and onto the work bench, after much banging and swearing I got all pieces separated, the intake is one whole aluminium piece and the exhaust is steel and comes apart into 2 pieces.

My best guess after looking at all the surfaces was the section where the exhaust manifold bolts up under the intake manifold, it's a triangle shaped section with 3 bolts.
What seemed to have happened years ago is that the bolt sheared off and the gasket fell apart letting moisture into the join, then the metal exhaust side began to rust creating an even more uneven and bigger gap. So I think all the noise and hot air I was sensing at the rear of the engine block was actually from this section and it was just blowing sideways and echoing, confusing me.

So I've just scrubbed down all the surface sections, gotten off all old gasket gunk, rust etc. On the really bad exhaust surface I've actually slowly sanded it down until it's flat to the naked eye, hopefully this will be good enough, because I don't want to mess about with mechanics. I'll need to order a new gasket for this section.

Another section I'm a bit worried about is where the two exhaust bits join, there's these big metal rings that sit in channels on one part that slots into the other, one of these appears to be missing, I've attached an image to explain it better. Anyone worked with these before, know how many should be in this section?

Thanks again for all your advice, as soon as I get the correct gasket I'll put everything back together and pray.

 

[BlackCat]

Some early 60’s only have one exhaust horn ring, but all have provisions for 2. Being a 3F, I’m unsure what you’re supposed to have. I’d replace the horn rings and springs and utilize the second provision for them as well. So you’ll need a total of 4 rings and 4 springs. For what they are, they’re expensive. The best deal I could find was something like $120 for all of them.

 

[martyjayFJ62]

Some early 60’s only have one exhaust horn ring, but all have provisions for 2. Being a 3F, I’m unsure what you’re supposed to have. I’d replace the horn rings and springs and utilize the second provision for them as well. So you’ll need a total of 4 rings and 4 springs. For what they are, they’re expensive. The best deal I could find was something like $120 for all of them.

That's crazy expensive for what they are.
If I'm searching online they're called "horn rings"?

Thanks for the info.

 

[BlackCat]

That's crazy expensive for what they are.
If I'm searching online they're called "horn rings"?

Thanks for the info.

There’s the part numbers. You’ll need 4 rings and 4 springs.

 

[mattressking]

There’s the part numbers. You’ll need 4 rings and 4 springs.

View attachment 1909853

Cut that number in half. This is 3F manifold. I don't want to say what I'm reading is gospel without holding the stuff in my hands, but diagram states 1 of each for 3F manifold, but I'd get 2 of each just in case either way.

 

[LAMBCRUSHER]

You’ll want to take the set to s machinist. Have the surfaces where I take and exhaust join milled flat, broken hardware removed and threads repaired. Have machinist replace gaskets at interface and torque to spec WHILE bolted to a head- or clamped to a flat surface in order to maintain alignment of the pairing before having their head mating surfaces milled flat. This ensures that the mating surface at the intake and exhaust are perfectly sealed and that the heads mating surface will also seal. The non-US 3f manifold uses a couple of sealing rings AND springs in the bore of the exhaust manifolds rear horn to seal that joint. You’ll want to take it in to have this done by a pro for the amount of effort and expense of gaskets if you want a reasonable assurance of success. Worth the cost and effort as long as you don’t cut the corner to get there. Hth.

 

[martyjayFJ62]

You’ll want to take the set to s machinist. Have the surfaces where I take and exhaust join milled flat, broken hardware removed and threads repaired. Have machinist replace gaskets at interface and torque to spec WHILE bolted to a head- or clamped to a flat surface in order to maintain alignment of the pairing before having their head mating surfaces milled flat. This ensures that the mating surface at the intake and exhaust are perfectly sealed and that the heads mating surface will also seal. The non-US 3f manifold uses a couple of sealing rings AND springs in the bore of the exhaust manifolds rear horn to seal that joint. You’ll want to take it in to have this done by a pro for the amount of effort and expense of gaskets if you want a reasonable assurance of success. Worth the cost and effort as long as you don’t cut the corner to get there. Hth.

OK so here's an update.

My approach to this vehicle is, get it functional for outback trips for as little money as possible, it cost me $3500 to purchase the car initially, I'm looking to avoid all extra cost involved with mechanics shops etc.

With that in mind, I leveled the intake and exhaust manifold join surfaces using a grinder and sandpaper, I ordered a new gasket for that area, which finally arrived.

I replaced all broken bolts, put the manifold back together and back onto the exhaust / engine block. I torqued down all bolts as hard as I can by hand.
I then actually put back on my old carby as I didn't trust the ebay one I had bought (it didn't have all matching vacuum line plugs).
One point, I hate the intake manifold, as it is all aluminium and seems prone to warping and sheering off threads, I guess this is aluminium for heat dissipation right?

So after everything is put back together I run it and the exhaust noise is much much lower, it went from sounding like a jet taking off to just a noisy 80s car.

Now that I can hear myself think when I work on it, I have discovered that the exhaust muffler has some pin hole leaks around the rim of it, anybody got some recommendation for fixing them? Should I just spot weld the holes?

Pic attached

 

[BlackCat]

My opinion? Torquing the manifold bolts “as hard as you can by hand” may contribute to an early failure and premature re-warpage. There’s a torque spec for a reason. If you have a slightly warped manifold, a lot of us have had good luck with the remflex gasket, specifically made for that reason. Also, the pinholes in the muffler I’d use something like JB weld or the like. Welding is not recommended on a muffler face since it’s thin and you’ll likely burn right thru it, creating an even larger hole.

 

[SteveH]

If the muffler pinholes are due to rust, then welding is out of the question. If they are an mfg. defect, then a very light touch with a wire-feed welder (and some experience) can weld those shut. Aim the wire at the rolled edge (thicker) and then aim back toward the hole as you weld. You will likely blow a few more holes in the muffler until you get the technique down. If you have done a lot of bodywork, you'll know how to do this without just torching holes in the muffler.