Glowing Catalytic converter plus knocking sound coming from it. I can pry at the converter and the sounds stops. Is it fuel being ignited in the converter due to a misfire? or is the converter just bad at 135k miles? any other ideas? I dont have a CEL/SES light on.

 

Bad cat. The rattle is the guts falling apart.
Glowing red is usually the engine running to rich.
Since the cats are bad I would replace them first.

 

Quit driving it before you burn your truck down.
If it gets any hotter the body will burn like a road flar.
Go start figuring out what is causing the problem.

 

could it JUST be a bad converter?

 

If it's glowing red after driving a while, it must be dang hot. You havea fuel management issue (running rich.)

1) The converter is rattling because the inside of it probably fell apart from being over-heated. Let the truck sit overnight and the converter get cold enough to touch, then smack it with your fist or a light blow with a mallet. It will probably rattle. If so, you need a new converter. Sometimes the loose parts rattle around in there and plug the exaust up causing more overheating and loss of power. If the pipes or mounts are loose, have a muffler shop look at it.

2) Does it run normally, have a miss-fire, or idle wierd? Lack of power? Noticed a "rotten egg" odor from the exaust lately? What kind of fuel are you running? Premium is a must, good fresh stuff. Plugs /wires been replaced recently? Check the connector on the air flow meter (with the truck off) and make sure there is nothing in the air box plugging incomming air (a mouse nest possibly) under the air filter.

Pretty sure Mike and the other Guru's will chime in here soon.....

Good luck,
David

 

That's what I get for taking 10 min to reply to this. Hi Mike

 

Truck Runs normally, no misfires that i can tell, no idle problems. its always had a lack of power in my opinion, no funky smells from exhaust. I only run premium, and just checked;no nests in the air box. Ill have a muffler shop replace the cats this week. I hope it is just a messed up converter. Ive had enough from this truck recently to deal with much more this year.

 

It is not a bad cat, it is an overly stressed cat do to too much gas.
The engine can't be running well, when was it last tunes, plug, wires?
It is obvious you are not mechanical so have it towed to a mechanic, checked for codes, dead holes, bad valves or failing injectors.
Believe me whaen I warn you, don't drive it, Discoverys burn like an over cooked marshmellow in halve the time.

 

new injectors 7k miles ago, wires and plugsjust 10k miles ago

 

seriously though, dont catalytic converters need to be replaced around 100k. im at 135k and theyve never been looked at. Ill lookinto the exhaust valves, but the motor would be idling rough if i needed avalve job. I woud notice something like that. the only other option would be the injectors, but they are brand new.