Exhaust Leak

[ealex]

Anyone have any tips how to track down an exhaust leak. Its manifesting itself as a slight tick under acceleration, coming from the passenger side of the block toward the front. There are 2 real possibilities - exhaust manifold gaskets, or the secondary air injection manifold. It looks like the previous owner tried to remove it, and in doing so the pipe is slightly twisted. The gaskets look to be original - so at 80K, their shape is questionable as well.

I just don't want to blow the $50 on diagnosis if it turns out to be the $5 gasket. All suggestions welcome.

[Steph]

usually, a front leak is at the jonction of the exhaust manifold and Y-pipe.

[ealex]

thanks. In this case the leak is top side by the exhaust manifold. Sounds like one of the front two cylinders, but definitely up top.

[Rovin4life]

if you suspect a leak in the secondary air use a smoke machine to show where the leak is coming from. to open the valve use a vacuum hose to open it up.

the leak will show itself.

[ealex]

unfortunately I don't have a smoke machine at my disposal. Trying to remove the secondary air injection manifold, the front mount is seized together, the pipe twists with the nut. Gonna work on it tonight...don't feel the need to cough up $260 for a new pipe. I'm thinking of removing it, sealing the ports used by the secondary air system and see if the leak is still present. If so - gaskets or cracked manifold, if not - secondary air...which means brazing, bending or replacing...

thoughts?

[ealex]

After a night under the rover, I'm not sure the ticking is an exhaust leak. There are no traces of carbon buildup anywhere on the manifold, pipe or engine block. Also, the engine stumbles a bit when revved up - leading me further away from the exhaust leak theory.

About a week ago I checked the condition of the #2? (front, passenger side) spark plug - clean and gapped properly. That's been the most interaction I've had with the ignition system thus far. The problem appeared 3 days ago as a audible tick during acceleration that is directly related to RPMs. Its louder when the engine is under load. Sounds like puffs of exhaust by the plug I checked. I pulled the plug and re-seated the wire, the threads are fine, the wire makes good connection with the plug.

After a long time searching for the location of the supposed exhaust leak (and finding none), I revved the engine up to ~2000 RPM, and it seemed to be misfiring during the acceleration, but ran smoothly if the acceleration was slow, and ran smoothly when idling. The ticking is very quiet at idle and when the throttle is steady.

So, by curiosity, I pulled the plug wire off the #2 plug - engine runs like it did - slightly rougher. The ticking is still there, and the stumble on acceleration is more noticeable. The wire is hot and does spark to the frame if held close. What makes me raise an eyebrow - no codes, no check engine light - nothing.

My questions:

1. Is it normal for the ECM not to notice a plug that is misfiring?
2. Do certain ECM codes not light up the check engine light?
3. Could the plug be done for without any exterior signs?

My thoughts:

1. Replace #2 plug - see if it makes a difference
2. Check #4 plug & wire
3. Get a stethascope and identify the source of the noise...
4. ???


Any help is appreciated.

[Rovin4life]

number four wire does goe bad from the heat. seen it a few times.

[ealex]

Apparently my 00 D2 runs VERY clean. I had an exhaust shop do an "estimate" to repair the suspected exhaust leak. It took 2 guys and hour to find it. No soot, no carbon build up. It was on the underside of the exhaust manifold gasket on the #4 cylinder. Ordered all new gaskets for the passenger side from gold coast rovers.

If the secondary air manifold is seized on, is there any safe way to get it off to check the rest of the plugs?

Thanks for all the help!