Catalytic Converter Replacement?

[msmyer]

Yesterday replaced my Catalytic Converter at 260,000 miles, on the nose. When I took the old converter off the honeycombs were filled with a white chalky substance. Anyone know what causes the chalky substance?

[msmyer]

[vibrologist]

it is probably melted substrate of the catalytic converter.

I found this info:

"A catalytic converter consists of an insulated chamber containing a porous bed, or substrate, coated with catalytic material through which hot exhaust gas must pass before being discharged into the air. The catalyst is one of a variety of metal oxides, usually platinum or palladium, which are heated by exhaust gas to about 500º C (900º F, 737 K). At this temperature unburned hydrocarbons and carbon monoxide are further oxidized, while oxides of nitrogen are chemically reduced in a second chamber with a different catalyst. Problems with catalysts involve their intolerance for leaded fuels and the need to prevent overheating."

"Fouling, clogging, melt-down and breakage of the ceramic substrate inside a converter are common conditions that can cause problems. Plugging is usually the end result of a melt-down, which occurs because the converter gets too hot. This happens because the engine is dumping unburned fuel into the exhaust. The excess fuel lights off inside the converter and sends temperatures soaring. If it gets hot enough, the ceramic substrate that carries the catalyst melts. The unburned fuel may be getting into the exhaust because of a bad spark plug or valve, but an overly rich air/fuel mixture is another possibility."

That mean: make sure your ignition system is in tiptop shape and the injectors don't leak. An OBD-II scanner can help determine if something is awry. I hope you did not drive for long times with the CEL light on.

[lannvouivre]

I don't know that it was actually melting down. When they melt down, it's really obvious and the honeycomb will actually be collapsed and distorted. Since you're at 260k, that's pretty good. Mine went at 110k right after I overhauled my engine