My 2008 4.2 has 250kkm on it. Things do need to be replaced. Some because of wear / tear or others because they break / broke. I was wondering about the cat. Do they wear out suddenly... no not clog but just stop doing what they are supposed to do ("clean gases")? I recently got a endoscope to stick up its "nose". Although they thing is not looking clogged... maybe some part around one area, I was wondering about the general aging. I am assuming the O2 sensor and monitoring system have some way of determining that it has tipped over but I guess the question is more will it "limp into old age" until it gets either clogged and cracked inside? I am hoping that I never have to deal with this although getting a "thumb quote" from a local muffler shop ($1100 for the part... ya right... :-0 ) will certainly put a lot of pressure on my wallet should things go south. The same shop didn't appear to know what I meant by a "back pressure" test sheesh! But that is kind of expected here in the great white north... at least with my experiences with shops.
How graceful does a catalytic age?
- Thread starter budwich
- Start date
Mooseman
Moderator
There may be some more learned members with an answer but I would think it just slowly loses its ability to work. Maybe check the downstream O2 sensor's activity. If it seems to bounce up and down a little following the upstream sensor, it may be on it way out. It should be relatively steady. Another way is to use an infrared temp gun while revving the engine about 2500 rpm checking the in and out temps. Should be significantly higher going out.
Attached is pdf of pictures of some of the cat area. There is no focus control on the scope so some are better than others. Based on age, they would seem "good" in terms of "flow thru" / clogging compared to ones that I have seen for new and / or clogged.
littleblazer
Member
- Jul 6, 2014
- 9,265
Some just drop off a cliff others slowly lose their catalytic ability. When they do start going you'll get a cel in the winter but none in the summer because the added heat helps with efficiency. Mines got 220k miles on it and still works fine. The v8s seem to go quicker... the escalade needed it around 210k... the work truck has 250k on the original. So long as you don't let it run rich they last a really long time.
ok... another question. I am not so much worried about the catalytic action itself.... more about "clogged" state which impacts engine running. Does a cat that loses is "cleaning" capability clog up eventually or the thing just lets "contaminants" pass thru "freely"... kind of a "chicken and egg" question... which comes first ... clogging and lack of "cleaning" or lack of "cleaning" and then clogging? I know that some of this is monitored by PCM "bogies" for the o2 sensors but just wondering about states of things.
littleblazer
Member
- Jul 6, 2014
- 9,265
Honest to God it depends. If it completely goes out it can't burn off anymore and will cake. If it slowly drops off I'd speculate it can still burn off particulate... if it starts breaking down it could potentially plug itself. Ive never done one in a 360 but the ones in the escalade were see-through when they failed. The vette (84) broke down and plugged itself.
Easy way to check is to see if the outlet temp is higher than inlet temp. Cats light off around 400... if you're getting a sizable jump (300 in 550 out say) I wouldn't worry about it. If the cat is getting very hot you have a restriction to flow... talking like well above 900. All temps in F by the way. Start it, warm it up and drive harder around the block and check it out. Pipe into cat should cool slightly as it approaches... runs on our cars are pretty short so it may not. And should be marked higher after.
aaserv
Member
I had 1 go out and never had a seconds warning. no cel nothing. Stopped at a light and when it turned green it was next to no power at all. Foot to the floor wouldnt do anything. Feathered it lightly and made it to a shop a mile away doing 15mph tops. Now granted once they put the new 1 on it made a huge difference but it being a daily driver I just hadnt noticed the gradual loss of power I guess.... Astro Van w V-6