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Unread 06-25-2013, 12:01 PM   #1
Candymancan
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using a infared therm to check if a cat is clogged ?

I was told to use one to check if my cat is clogged from my 5.9 burning oil for the 2 1/2 years ive owned it.. Since i have fixed my plenum and replaced the upstream o2 sensor.. So I got my infared thermometer out and drove the Jeep around for like 25 minutes, and checked my cat in the front as the pipe enters and it was 220f, and I checked the cat as the pipe comes out and it was 550f. The pipe as it goes into the muffler was 440f..

So does this sound good ? Meaning my cat isn't clogged. The cat seems pretty cool in the front but piping hot in the rear.


EDIT: I was reading the thing wrong.. gah

Ok I decided to check the thing again because 220 seemed way too cool..Well durr I had it on C and not F.... So I had someone rev the engine to 1500-2000 rpm and I checked it again..


Whelp the front was reading 470F, the rear was reading 410f.. So I guess the cat is clogged.. Looks like I have to save up for a new one.. humph...

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Unread 06-25-2013, 12:09 PM   #2
B93
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Yeah, I think if the cat was clogged the temps would be higher in front of it (like between the manifolds and cat). Although 220f seems pretty cool for exhaust gases, are you sure it's giving an accurate reading?
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Unread 06-25-2013, 12:23 PM   #3
Candymancan
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I can check it again, but it said 220f in the front and 550f in the rear. I've used the therm before on the Y pipes near the oil pan and they were only like 330f, the exhaust manifold gets to like 500f, so im guessing because the cat is much further back from the Y pipe it would probly be cooler.. I'll check it again I suppose. Its a cheap thermometer from harbor freight however it does seem pretty accurate as I've used it on my coolant hoses and the engine itself and they all show like 200-220f, oil pan is 210f, transmission shows its around 180-200f in park anyway.

Another question, the muffler you know how they have those little weep holes in the front on the bottom to drain water from condensation.. Is it normal for exhaust to leak out of that hole and make a phhhhhhhhpph type noise like you would hear from an exhaust leak ? Because mine you can hear it just standing by the passenger door its deff pushing a lot of air out of that hole.. My cat and muffler are original btw
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Unread 06-25-2013, 12:24 PM   #4
B93
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ahh okay. I guess all that makes sense since the cat's job is to heat up the exhaust gases. I wouldn't bother checking again, what you said makes sense
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Unread 06-25-2013, 12:36 PM   #5
Candymancan
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No your right it only takes a min to check. Im just inside cooling off in my house because I was working at a customers house doing landscaping.. Its like 95f outside and muggy and I about died lol. I thought 220f was pretty cool too.

I know you can also do a backpressure test with a gauge but I don't have one of those, nore do I want to spend $100 to buy one to just check, Im just trying to get all my MPG back I lost from my plenum leaking oil.. Fixing the plenum deff stopped all my oil loss, but what was weird was my gas mileage dropped fixing the plenum by 1-2 MPG.. So I replaced the upstream O2 per what people said and its back to 12-12.5mpg.. However its still lower then it used to be when I first got it.. Spark plugs are new, distru and rotor are new, wires aren't that old.. So the cat was suspect next.. but if its only 220 in the front and 550 in the rear I guess It working perfectly.
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Unread 06-25-2013, 12:51 PM   #6
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I say at 550 degrees you may just be measuring the heat shield. The internals I am sure are 700-900 degrees to perform its function. But over 1200 degrees the internals melt and clog...

So I say at 550 degrees your CAT should be okay unless is is hollowed out versus being clogged. Have you ever heard it rattling? Rattling means it is breaking up and when it breaks up, parts of the catalyst shoots down you pipe... can cause clogs but for sure the cat is not working properly.

With ODBII and you having a post cat O2 sensor you would throw a code, but not always. Mine was breaking up (rattling), felt sluggish on the throttle and I felt heat radiating from under the Jeep after driving, but never threw a code. My new Magnaflow High Flow Cat is awesome and "woke up" the beast now that I have a Flowmaster Super 40 and 3" exhaust. I don't regret spending the money replacing the setup when I discovered it rattling and going out. At first I was like, "@#$%, another thing to fix..." But now, I am glad I did!
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Unread 06-25-2013, 01:32 PM   #7
Candymancan
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No it isn't rattling when I bang on it..

Trust me I wasn't measuring the heatsheild. I was holding the laser on the rusted piping on the inlet and the outlet of the cat.
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Unread 06-25-2013, 02:08 PM   #8
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I found this video an interesting watch, especially his discussion about voltage changes in the O2 sensors.

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Unread 06-25-2013, 02:46 PM   #9
Candymancan
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Ok turns out you were right B93 220 was cool.. I had the stupid therm gun on celcius and not F.. I had a friend rev my Jeep and the front of the cat was reading 480f.. The rear was 410f.. So I Guess my cat is clogged.... gah... insert face palm.....

Soo I guess that is where my bad gas mileage is coming from now.. Sooo does anyone have any recommendations of a cheap cat that is equivalent to the 5.9's stock cat ? I don't have a lot of money so I cant afford fancy magnaflow cats assuming they are expensive anyway..

What about those universal magnaflow cats ? They are $109 on advance auto


http://shop.advanceautoparts.com/web...983%7CL3*15311
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Unread 06-25-2013, 04:20 PM   #10
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EXcellent video.
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Unread 06-25-2013, 04:58 PM   #11
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Quote:
Originally Posted by Candymancan View Post
Ok turns out you were right B93 220 was cool.. I had the stupid therm gun on celcius and not F.. I had a friend rev my Jeep and the front of the cat was reading 480f.. The rear was 410f.. So I Guess my cat is clogged.... gah... insert face palm.....

Soo I guess that is where my bad gas mileage is coming from now.. Sooo does anyone have any recommendations of a cheap cat that is equivalent to the 5.9's stock cat ? I don't have a lot of money so I cant afford fancy magnaflow cats assuming they are expensive anyway..

What about those universal magnaflow cats ? They are $109 on advance auto


http://shop.advanceautoparts.com/web...983%7CL3*15311
Not sure what your stock 5.9 cat is but best to measure the inlet/outlet pipe diameters along with the length on your existing one for easier install. That magnaflow in your link is only 17" long which may be too short unless you want to add an extension pipe onto it. Also has 2.5" inlet/outlet pipes.

I went with the Walker Ultra Direct fit which is about $16 more but not going for high-flow on my 96 4.0. Still has more flow/sound than the OE one and it's 22.25" long which is the exact size along w/2.5" inlet & 2.25" outlet.

And don't forget the discount codes if you go through Advance. I just ran that magnaflow through the cart and it's $69.99 instead of $109.99 using TRT41 ($40 off). RMN25 in the below link is about used up and only gives you 30% off.

http://www.retailmenot.com/view/adva....com?c=4582125

BTW Coralman, also thought that was an excellent video and just ordered a $20 thermal sensor w/laser off Amazon.
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Unread 06-25-2013, 05:52 PM   #12
Candymancan
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My exhaust system looks stock to me.. The Ypipes are small 2.25, then once they go past the oil pan it gets slightly bigger probly 2.5 inch, then stays the same size to the muffler but exiting the muffler the pipe is much much bigger looks like its 3 inches and then of course the tail pipe is 4.

Old pictures I took awhile ago but this is my exhaust







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Unread 06-25-2013, 11:44 PM   #13
Uniblurb
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Looks stock to me too Candymancan. If those pics are 2 years old is your muffler still in good shape? Looks like you may need a muffler in addition to cat if not. It would be nice to save that tail pipe since a new one is going to be a whole lot thinner steel, maybe less diameter, unless you go to some pricey stuff.
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Unread 06-25-2013, 11:52 PM   #14
Candymancan
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Yep muffler is still in good shape. No holes or anything. Im quiet surpised how long this stock system has lasted. Our 4.0 has gone through 2 mufflers and 1 cat. Original muffler had a hole in it many years ago.. The second one developed cracks from the pipe exiting it from stress or something. The cat the heatshield fell off it from rust ect.. Altho the previous owner on my 5.9 had it in many states through its life the 4.0 has been in Virginia since day 1 so lots of salt on the roads.. Im noticing my 5.9 starting to get very minor rust in spots from the 3 years its been on the road here lol.

In fact if you look at the first pic you see the 4.0 in the background and its newer exhaust lol.. The rusted to **** welds that shop did to it as well.

I mean I dunno what the interior of the muffler looks like.. But it sounds good, the only thing I noticed is a exhaust leak from the little drain weep hole you see in the pictures but I think that's normal. The rust on it is like surface rust.. If I bang on the muffler really hard its fine so no weak spots.. The clamps tho from what I saw today are extremely rusted and one is broken lose almost. Guess I'll bring it in to a shop I called yesterday and have him look at the Jeep and tell me what itll cost to replace my cat.

You know what I wish I had the money for is one of those borla exhaust systems.. They sound absolutetly amazing and make the 5.9 sound like a real scary beast.. The flowmasters sound too hollow.. Like a sports car or something
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Unread 06-26-2013, 12:53 AM   #15
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Well that's good your muffler is still in good shape. Thought maybe the muffler would be destroyed in trying to get the cat outlet tube out of the inside of the muffler inlet tube but a shop will probably just cut/weld it. Looks like somebody maybe enlarged the weep hole in the front of the muffler but maybe not a bad thing since mine condenses water like crazy and needs a way out.

LOL about the 4.0 exhaust in the background and I've gone through a few mufflers and 1 cat myself. I was too busy looking at the o2 sensor wires which should probably have insulation/heat cloth on them. Ha! You could mine the salt off the road around here in the winter and it's terrible!

Not sure what a shop will charge you for a cat but the below MagnaFlow looks pretty good for the price and a direct fit. Around $100 after that $40 off discount code is used.

http://shop.advanceautoparts.com/web...archTerm=23226

Haven't heard a Borla exhaust but I can see why many with a 5.9 go for 3" all the way if you have the bucks. Didn't realize there were so many restrictions throughout the exhaust, y pipe is 2.25", and thanks for sharing the pics!
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