Well heck, after 157,000 perfect miles, I have to replace the lower intake manifold gasket, then the next week my passenger's side front cat converter goes to rattling.
I suspect the guts have broken up (much like Travlnman's).
Darned replacements are expen$ive!
Anybody fitted an aftermarket replacement or know of a good source?
The guys at the local independant shop I use are good folks and suggested replacing the down tubes and adding an aftermarket hi-flo cat and just fabricating whatever pipe I needed to get back to my muffler.
I go the impression this would run both downtubes into a single pipe, use a single hi-flo converter and then go into the muffler.
This would require eliminating the second set of O2 sensors, but I believe that can be done fairly easily without casuing problems.

Any experience or advice?

 

Hmmm...I've never done it so I wouldn't know who is best, but I would think you would need 2 high flows instead of 1. I know it's been done about a million times, so it should be fairly easy to compensate for the 2nd set of o2's.

 

Well, the rattle has gotten progressively better over the last few days.
Now it has basically healed itsself - at least for the time being. I'll let sleeping dogs lie.

 

A good muffler shop should be able to fab up a set of pipes for 2 high flow cats very easily. I have seen high flow replacements for as cheap as $68 ea. They did not have the boss for the o2 sensor, but that can be added in the pipe, again, by a good shop. The ones with the boss for the sensor were about $150ea. I'll try to find the info again, and post it here.

 

My passenger side cat did the same thing. Went to a muffler shop and had them remove the offending cat and replace it with a pipe. Cost $40 and the truck still passed the smog test. go figure.

 

your cat sounds like blews its guts out like my dads taurus did. I would leave alone unless you have to pass a smog test and fail.

 

Brian, just straight pipe it all the way back.... It's the only way to go. Cheap and louder, and it's not like it's gonna effect your engine at 157,000 miles.

 

Brian, I was thinking, I know it's dangerous. I believe your cats may have been damaged by burning coolant when you had your leak. My wife had an SUV by another manufacturer that blew a head gasket at 26k. Shortly after, the converter went bad, presumably from burning the coolant, as it was leaking internally.

 

Thomas,
You might be right. The cat converter that went to rattling is on the same side the leak was on.
The rattle is no longer an issue really - at least for the time being. The rattle is so slight I rarely hear it.
Considering the cost to correct, I'm driving it as-is. It hasn't seemed to affect performance in any way. Acceleration is good. MPG is good.
I'll let this sleeping dog go undisturbed.

 

Well spoken, as usual.

 

I appear to be in the same boat with Brian (except my passenger side rattle is getting much worse each day). I thought it was one of the heat shields, but none of them are loose.

I have an E-Check due up in May, and im damn sure its gonna fail.

Would I still pass if I took Homer's advice? How do you dump the cats, run straights and fool the computer?

Or is SAR Roy's advice good too? Removing one cat will affect the computer as well?

Any and all advice appreciated!!

 

Ron,
If you eliminate a cat converter (one or both), you can expect to fail your emissions test.
You can fool the OBD II computer so you don't get a check engine light, but you that won't fool the emissions testing equipment.
It analyzes what comes out the pipe and doesn't care what your computer is thinking.
But, you might not fail as-is. If the guts are still in the converter, just rattling around, it might still function well enough to get the job done.

 

Cut those sons of you know what off!!!

 

Hmmm I can live with the rattling till I take the E-check, its worth at least that. If not for the test I would definitely cut them off. I see other F-150's with 2 straights coming out the back, and would like it like that as well, just need to figure out how to pass the e-check when I do this, as it seems possible. Man I knew I should have stopped the guy I saw with dual pipes and ask him how he passes...(although he probably sill has the cats.)

What if its the rear passenger cat? I am not sure if its the one or not, but if so, isn't only good until the truck warms up? The front cats are for cold starts, and after its warm, the rear ones do not do much..Or am I inncorrect?

 

if this helps anyone, the dealership should replace them for free for 8years/80k.

brian, i dont think this applies to you....