Cat Questions

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SoCalJohn

SoCalJohn

10 Year 15 Year 20 Year
Joined
Jun 6, 2005
Threads
14
Messages
129
Location
Orange County, CA
It's almost Friday .Ok folks, who knows? Are my cats welded in or clamped in on my model year (91). They are original. And if clamped in, is this something I can handle? I can use tools but no welding experience.

If I go after market, it that a good idea (magnaflow)?
Slomo, I saw you participating in a post recently, did you end up sticking with OEM? and make any changes?

I believe my exaust leak (high pitch whine on hard acceleration) is coming from right past my cat where it joins to the exaust piping.

What should I expect with new cats?? besides a skinnier wallet:D
 
Shoot, you know what i can't remember if they're clamped or welded! I've been under there more than a few times and im drawing a blank.. someone will chime in on this.

As far as the brand of exhaust.. i don't know how many options you'll actually have. Their can't be that many folks making cats for our rigs out there. Magnaflow may be the only one.

You shouldn't really be expecting a whole heck of a lot coming from your cat after you replace it. Depending upon how bad it is clogged up (16 year old rig - original cat?) you might gain some gas mileage, but that might be about it. No horsepower gains really. It may be quieter too.

If you just have a exhaust leak where you describe it, i wouldn't bother spending the money on a new CAT, just have them fix the problem where the cat joints.
 
Just replaced my cat not too long ago. It was clamped on. Got my done, since I was having problems matching it all with my header.
 
What peeves me is going to two different shops, and no one wants to take the time to find the leak or repair, they just want to replace everything!! I wait for some feed back Thanks
 
SoCalJohn said:
What peeves me is going to two different shops, and no one wants to take the time to find the leak or repair, they just want to replace everything!! I wait for some feed back Thanks
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I wound up keeping the stock cats for now, I had one cut and turned about 5-10 degrees to clear my sliders. I currently run a Magna flow muffler with the factory exhaust tubing. I am probably wrong but I think the 3FE's cats are welded due to thier side by side format vs inline for the 1FZ folks. If you look under there you will see a metal strip about 1" wide at each end of each cat if they are clamped in or perhaps a flange that bolts them in. If they are you should be able to handle it but clamped exhaust parts can be very stuborn and fight removal.

Regarding the Magnaflow cat you sighted, almost all aftermarket cats that are non OEM direct replacement are a universal fit and have bare tubing coming out of each end. A marked "high flow" cat will reduce a littel back pressure but nothing you would feel seat of the pants. Cats for california use (CARB certified) are usually costlier than the 49 state cats and run around $200 each. You definitely want to be sure you need them before throwing down that much cash.

I am curious what leads you to believe it is coming from there. Has someone made that reccomendation or is that just where you are hearing it? I don't remember if the FJ's have a resonator like the FZJs but when that is removed we get a high pitched wistle under hard acceleration. Could be that it has gone out, if you have one at all. One really good way to find an exhaust leak if you have one is to start up the rig in the morning after it is totally cold and let it idle. Get under it and look for any water other than the exhaust tip. They produce water when cold and it will usually drip out or at least wet where there is a leak. You can also get under there and look real well with a flashlight if neccessary and you should be able to find black soot/carbon buildup around any leaks. If you plan to make it on Monday night I would be happy to take a look at it. If it is just a simple leak and the cats/exhuast is in good shape I could weld it up for you, just not in the parking lot. :D
 
On my 94 the cats are bolted on and are removable. I know this because I had to remove one of them to remove the heat shield that was causing a rattle. Turns out the heat shield was not the problem. My Hanna Sliders were just barely touching my cats. I tried clearancing them with a grinder but I still have an intermittent rattle. I need to get back in there with the grinder again. SoCal John I also have a high-pitched whine on hard acceleration. I however removed my resonator when I installed the 4x4 Labs rear bumper. I never hear this whine before, even after the removal of the resonator. I began to notice it this year coming back from a trip to Ocotillo Wells. It’s now very noticeable if I have the radio off. I think I have a cracked manifold but not sure yet need to investigate further. I would guess that my mileage would suffer with less back pressure if I had a cracked manifold but it has not. Who knows maybe it could just be the resonator but my gut tells me differently. I usually know when my truck makes a new sound and this one is new to me.
 
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SOCALFJ said:
Hey Tare, good tip on the slider rattle. I need to attack mine.. it's driving me nuts dude.
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Not sure what year yours is, if it's a 93/94 then your cats are parallel to each other. They will make contact on the rear upper portion of the cat protection. Once you remove the slider and know what to look for it will be clear where contact point is. Just grind away, make sure to remove more material then you think you will need. These LC bodies move around quite a bit and if you do not remove enough material your rattle will return.
 
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SOCALFJ said:
Hey Tare, good tip on the slider rattle. I need to attack mine.. it's driving me nuts dude.
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Slomo said:
I wound up keeping the stock cats for now, I had one cut and turned about 5-10 degrees to clear my sliders.
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:rolleyes: :flipoff2:


If you remove the slider you will see a wear mark where it is hitting and rattling. Ours are almost inline and end to end unlikes Tares. Ken makes the sliders for maximum clearance and sometimes they sit too close to the cat that is about 5-10 degrees off of true vertical. The follow the v-bend in the cat plate and only have about 1/4" clearance. Give a shout if you need any help.
 
Almost forgot, how is it going John? Any luck finding the culprit?
 
Sorry, guys on the road all weekend, Easter family stuff.... I am going to inspect the whole system closely and look for those carbon marks and rust spots. My gut feeling initially, was it was coming from the rear of the vehicle, but the last shop pointed out a leak directly after the cats. I will be seeing you all Tonight, I can give a test drive to a few of you, and you will hear it.

I had the rattle for a long time, thought it was the shield, but it was the first metal bracket past the cats, which had rusted through. Spot welded it, and now no more rattle!!

All the comments and input were great, but the way...Thanks a bunch.
:beer:
 
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