Exhaust Manifold cracked?

[Simba]

Hey all,
The Wagoneer has developed a tick from the right bank toward the front. Sounds like an exhaust leak to me but as I looked around the manifold I cant see or feel where it is coming from. Probably need to tear into it to find out but what I am wondering is if it is common for the right manifold to crack under the heat riser shield that wraps around it. If that is the case then it would be difficult to see.

Thanks!

[tgreese]

No, I don't think so. Typically they won't crack unless you shoot cold water on a hot manifold - BTDT.

[Simba]

No, I don't think so. Typically they won't crack unless you shoot cold water on a hot manifold - BTDT.

Thanks for the info. Haven't done that so guess I'll keep looking.

[Tatsadasayago]

#8 gets the least oil pressure in a stock AMC V-8, so that tap you hear my be lifter clatter. I would suggest getting a 24" piece of rubber/plastic tubing and use it as a stethescope to identify the source of the sound. It could be a manifold gasket, cracked manifold, heat riser gasket/donut or rocker/lifter.

[ShagWagon]

Run the shop vac backwards through the tailpipe so you can feel where the air is leaking at the manifold side.

that way you won't burn your hands.

When you feel the air leak, then You go from there.

[Simba]

Thanks for the input guys. I'm going to try the shop vac idea. Already listed with a stethoscope. May be wrong but at this point I don't think it's valve train

[FSJ Guy]

Exhaust tick leaks will also come and go according to the engine/manifold temperature. Some are louder when cold. Some are louder when hot. Just depends on the nature of the leak...

If you pull the plug wire near the noise location and it goes away, you know it's an exhaust leak. If you still hear the tick, it could be in the valve train.

[Simba]

Exhaust tick leaks will also come and go according to the engine/manifold temperature. Some are louder when cold. Some are louder when hot. Just depends on the nature of the leak...

If you pull the plug wire near the noise location and it goes away, you know it's an exhaust leak. If you still hear the tick, it could be in the valve train.

Great tip. Thanks. It does change with temp

[ShagWagon]

I would put a smal socket on the manifold bolts and see if any are loose for the easy fix hopefully.

[Simba]

I would put a smal socket on the manifold bolts and see if any are loose for the easy fix hopefully.

Isolated it to number 2 cylinder. Bolts are fairly tight. Thanks!

[Stuka]

Check the air injection bolts. That's where my exhaust leaks have always been.

[Simba]

Thanks everyone, I appreciate the help!! Looks like the gasket is bad on #2.

[UZI4U]

Is there any truth to using gaskets for the exhaust manifolds is unnecessary? I have read that the heads and manifolds are machined well enough that gaskets aren't needed. This was after I had put gaskets in mine and I haven't been motivated to take them out and try it.

[tgreese]

The exhaust manifolds came from the factory with no gasket, iron on iron. The connection to the pipe is steel on iron too, depending on the year. The later manifolds have no place for the "doughnut" gasket - it's part of the manifold casting. In the '70s, steel doughnuts were used for a while.

Typically the exhaust manifold connection on the V8s do not leak unless someone messes with them. The 258 manifolds tended to develop leaks though. Once they leak a little, the exhaust gas erodes the machined surface and the manifold won't seal without a gasket. The typical composition gaskets (FelPro etc.) have a finite life, and will eventually blow out. The composition doughnuts are particularly bad about this.

[Tatsadasayago]

In my experience it is best to clean both surfaces and bolt the stuff together. The best gasket alternative is RamFlex gaskets but they are expensive as hell.