Break at Catalytic Converter

[95GS]

The exhaust pipe has broken just in front of my cat. converter. (3800) The cat. converter is an undersized 'universal model' installed at a muffler shop years ago. There is no stainless steel flex joint, only welded tubing, and this could be why the pipe broke.

 

One mechanic says remove the converter, install flex joint in its place.

What is the stock configuration - is there a flex joint in the system?

Does a replacement converter include a flex joint - would you buy a used converter?

 

[Schurkey]

Buying a used converter is insane unless you know the history of the thing...and then it's only slightly insane.

 

"New" converters are not that expensive.

 

On my Ws, there is no flex joint except for the spring loaded pipe-to-manifold connection, where the pipe rotates on the manifold via a rounded "donut" gasket.  Yours may be different.

 

"Replacing" the converter with a flex pipe...that "mechanic" must be a mucking foron.  The Federal Government will assess him a $10,000 fine for that "service" if they find out about it.

[Imp558]

he's right there's no flex pipe on your car. in some states and I don't know which ones it is legal for the owner of the vehicle to replace the converter with a straight pipe but no one in their right mind would ever use a crappy piece of flex tubing. it's worth it to just go get a universal converter the right pipe size which should be two and a quarter because that's what my 96 Regal came with

[95GS]

Thanks guys - right, I see converters are not that pricey.

My car also has the spring kit w/donut gasket - so this must be deemed sufficient to accommodate the engine torquing back & forth.

Now that I know there is no missing braided stainless joint, I may have it welded back as is, possibly with a sleeve over the joint,

since the converter is intact - no holes, and no apparent congestion/power problems.

Can't really do this until a fuel odor has been identified, in case fuel tank has to come down.

I hadn't considered that cheap flex pipe, though it's great for emergency repairs - easy to cut and clamp on.

Didn't know about that federal law, pretty serious. I think emission regs must be more relaxed in Canada, or at least in my province.

We don't have compliance testing or any other blanket emission inspections for owners.

[Schurkey]

he's right there's no flex pipe on your car. in some states and I don't know which ones it is legal for the owner of the vehicle to replace the converter with a straight pipe

No.  It is a violation of Federal law to disable the emissions system of a vehicle.

 

Some states don't test emissions, and the Feds don't prosecute unless it's a business...but it's still illegal.

 

Wanna get really picky?  It's illegal to remove a functioning OEM catalytic converter even if you replace it with an aftermarket catalytic converter.  If you think you can cut the factory converter off of your new Ferrari or 'Vette, and replace it with some "high-flow" aftermarket exhaust...you'd better be able to prove that the OEM system had failed and was not covered by warranty.

[95GS]

Picayune indeed!

[95GS]

Ferrari or 'Vette?

 

Doh!

 

Could have had a  V8  Tesla!

[95GS]

"New" converters are not that expensive.

 

So far I've only seen the small cylindrical 'universal' converters. I remember the original being a larger flat rectangular unit.

Are these still available? Won't the larger one have better flow?

 

 

On my Ws, there is no flex joint except for the spring loaded pipe-to-manifold connection, where the pipe rotates on the manifold via a rounded "donut" gasket.  

 

The pipe-to-manifold connection uses two bolts. Obviously a hot junction.

I intend to use anti-seize compound on them - is there any reason not to use it here?

A service manager told me it was a bad idea, without a good explanation...'could come loose'...??

 

Does one use anti-seize on exhaust manifold bolts/nuts, or does it make no difference due to extreme temps?

 

[Schurkey]

I wouldn't get too concerned about "converter flow", any of the monolithic/honeycomb converters will flow better than GM's old pellet-style.  I suppose GM was done with the pellets by the time these W-bodies were built.  Anyway, if the converter is sized to the engine, I think it'll be fine.  I'd be more concerned with ground clearance.

 

 

 

"Best" policy is to use brass nuts on steel studs.  Brass nuts/steel stud kits are available in SAE or Metric sizes at any NAPA or "real" parts store.  I apply anti-seize to the studs anyway, although it's probably not needed.  You may have to look around to find studs/nuts suitable to replace the bolts.

 

If you can't find suitable brass fasteners, I would anti-seize the bolt threads and reduce the torque setting by about 20% due to the threads being lubricated.

[95GS]

Thanks Schurkey - Both ends of the honeycomb look whistle clean, so I'm keeping it!

Didn't think of brass. Of course it won't oxidize or bind, but neither is it strong enough for bolt/stud material.

The bolts in this case thread into the manifold, no nuts, so steel it is.

Are stainless steel bolts ever used for such applications - high heat & rust proof?