Gap in exhaust manifold (1 Viewer)

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How did this happen and what should I Know before trying to fix it?
IMG_20141025_152506057.jpg
 
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It definitely SOUNDS like its leaking. As for testing it, I haven't. Could it just be that the gasket is blown completely out? Is there even a gasket? Maybe the ring and spring gone? I'm basically flying blind here and any help is way appreciated.
 
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It definitely SOUNDS like its leaking. As for testing it, I haven't. Could it just be that the gasket is blown completely out? Is there even a gasket? Maybe the ring and spring gone? I'm basically flying blind here and any help is way appreciated.
If you take a look at that link, you'll see that the horns are held on with the rings and springs (the springs push the rings out to make a tight seal).
I would only replace those rings and springs to fix an exhaust leak there if I already had the manifolds off.

You can usually hear an exhaust leak tick while driving. If you blow air or smoke (some shops have smoke machines for this purpose) back up through the tailpipe, you should be able to identify the source of the exhaust leak.

Other common sources for exhaust leaks are the intake/exhaust manifold gasket and the EGR gasket on the j-pipe (goes from bottom of exhaust manifold to EGR cooler).

For replacing gasket on j-pipe without removing the manifolds, see post #6 here:
https://forum.ih8mud.com/threads/massive-ticking.821263/#post-9408862


EGR System FJ60_gaskets_labeled.jpg
 
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OK. I think I see whats happening now. Can the front horn be removed without removing the entire manifold? I dread the thought of dealing with that pasta salad of vacuum lines sitting in there.
 
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OK. I think I see whats happening now. Can the front horn be removed without removing the entire manifold? I dread the thought of dealing with that pasta salad of vacuum lines sitting in there.
You might be able to remove that horn without removing the rest of the manifold, but I would not recommend it. Maybe others would/have done it and can post up to discount my assessment.

As I mentioned before, if I had positively identified an exhaust leak through either horn, I still would only address and fix that leak if I had the manifold assembly removed from the side of the engine...

Intake leaks will affect idle/performance. I'm not so convinced that exhaust leaks make a huge difference...

...unless you got flagged for it trying to pass emissions?
 
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I dread the thought of dealing with that pasta salad of vacuum lines sitting in there.

Yeah, it might seem overwhelming...until you become more familiarized with each of the Emission systems and the components that make up those systems...

While it might not immediately appear so, there is a logic behind the series of steps for pulling the manifold assembly...

One thing you could do, to become more familiar with the Emissions systems (then they won't be so overwhelming) is to run through the series of test procedures for each system, as outlined in the Emissions Factory Service Manual (FSM).

Do you have a copy of the Emissions FSM?
 
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I'll take your advice then. I'll first try to nail down any other possible leaks and if I can't find them there, I'll tackle removing the manifold. Thanks for all your help Slow Left. The only reason I noticed that gap is that I thought I heard a leak and when I popped the hood, there it was,
so I assumed that was the problem.
 
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I'll take your advice then. I'll first try to nail down any other possible leaks and if I can't find them there, I'll tackle removing the manifold. Thanks for all your help Slow Left. The only reason I noticed that gap is that I thought I heard a leak and when I popped the hood, there it was,
so I assumed that was the problem.
Alright. I identified an exhaust leak at the j-pipe gasket last winter...on a sub-0 morning, I saw the vapor puffing out of the gasket...but I don't recommend this method for identifying an exhaust leak...much better to live in a warmer climate!!
 
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The only reason I noticed that gap is that I thought I heard a leak and when I popped the hood, there it was, so I assumed that was the problem.
That gap looks more or less about the same size gap I have in the front horn on my exhaust manifold...and I just got done installing new rings and springs...so again, I'd look for further confirmation (like a smoke test) for where your expected exhaust leak is coming from...

Those horns slide in and out to find the right distance to align with the bolt holes in the side of the engine to which the manifolds mount...so that 'gap' is probably just the correct distance for the horn in order to align with the bolt holes...and not necessarily an indicator of an exhaust leak.

The exhaust leak past the rings/springs inside the horn can't be 'seen'...except through a smoke test...

Hope that helps...
 

Landpimp

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you can use a piece of hose to listen for the exhaust leak, one end in your ear...other poking around for the leak.

that gap looks pretty normal to me
 
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Your manifold "horn" gap looks normal. Here's another rebuilt one for reference.
If an exhaust leak can be heard from this spot, the sealing rings inside the manifold have not "blown out" as they are like piston rings in a piston and locked in a groove. What can happen sometimes is they can rust and bind into a non-sealing position and the exhaust leaks by. I always wondered if spraying something like PB Blaster (with the engine off and cold) in that gap could possibly help "unstick" the rings. Never tried it.

gap.jpg
 
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The only reason I noticed that gap is that I thought I heard a leak and when I popped the hood, there it was, so I assumed that was the problem.

I just thought of another possible source for exhaust leak near that ex manifold horn...there is a Check Valve on the Air Injection Rail (see image below) that allows air to be pumped from the smog pump, through the ABV/ASV and into the exhaust manifold through the air injection rail. It is a one-way valve...allows the air to flow in, but prevents exhaust from the exhaust manifold to flow back into the ABV/ASV...but when it gets old and fails, it will allow flow both ways....and if the housing rusts through, it will allow exhaust to escape...causing an exhaust leak.

There is a second check valve (see image below) on the skinny down pipe that connects into the exhaust down pipe (that comes off the bottom of the exhaust manifold). Works on same principle as check valve on the air rail...but when the ABV/ASV diverts the air pumped from the smog pump away from the air rail and down into the exhaust...

You should be able to find the check valves at a local aftermarket auto parts store, but they are like $25. The one on the air rail is easy to replace. The one of the skinny exhaust pipe not so easy.

If the check valve on the skinny pipe that comes of the exhaust down pipe is shot, then exhaust can come back up the rubber hose that connects the skinny pipe to the pipe leading into the ABV/ASV assembly. Check to feel if that rubber hose is hot. Someone has previously reported that hose smoking.

To remove the exhaust down pipe, first remove that heat shield that is mounted onto the driver's side frame rail by accessing the 3 bolts from outside the truck under the L front wheel well.
Start soaking with PB penetrating oil the 3 studs that hold the exhaust downpipe onto the bottom of the exhaust manifold every night or morning days before you try to break them free.
Same with the 3 bolt's nuts that hold the down pipe to the front of the cat and the bolts holding the down pipe to the two fastening setups.
Make sure when you reinstall that you put a new donut ring exhaust gasket between the down pipe and the exhaust manifold. Use new nuts and apply copper antisieze on the stud and bolt threads. Use 3 new bolts and nuts for the cat/exhaust pipe too (and maybe new donut gasket here too).

Once you have the down pipe off, you should finally have enough leverage to get that stubborn check valve off. Put an new one on with copper antisieze on the threads before you reinstall the downpipe. Save and reuse the rubber hose that goes between the check valve and ABV/ASV; they have a bend to them and are difficult to replace with aftemarket. Doesn't hold vacuum, so if it leaks a little air, don't worry too much. Important thing is that the check valve doesn't let exhaust back up into it.
Air Injection System FJ60_arrows.png
 
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Another thing that you could do to help you diagnose what is going on in the engine is to install a vac gauge in the cabin of the vehicle.
You can readily install one in the cabin by tapping into the A/C idle up port next to the brake booster port on the back of the intake manifold.
Run the 3mm line into the cabin through the hole in the firewall where the choke cable goes through. SunPro makes an inexpensive gauge (~$20 at Advance Auto or Pep Boys and the like).
Then find an appropriate place to install the gauge in the cabin. I cut a 2 1/8" hole to the right of the steering wheel.

Reading the vac as you drive will give you information about what is going on in the engine. See image below.



 
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Holy crap. I seem to have stepped off into an actual community that likes to help the noobs. Now I feel much more confident about tearing into my Cruiser. Thanks for all the help and info guys.
 
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Holy crap. I seem to have stepped off into an actual community that likes to help the noobs. Now I feel much more confident about tearing into my Cruiser. Thanks for all the help and info guys.

Well...at worst MUD is full of capable guys...optimists who don't know the meaning of the word 'quit'...

...tear away!
 

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