I found out the boneyard can not sell cats. That was a dumb idea anyway. I called the Firestone shop in town, they *think* it would cost around $800.00 to replace just the one bad cat, and that is if they can get the part. No thanks, I can replace the entire assembly myself for less than half of that.

I put my truck up on ramps yesterday and got under it with a print-out of the exhaust/cat assembly from Rock Auto. I studied it a long time to be sure I am buying the right part. I also studied the exhaust itself, and am sure I can do the job myself. I may even replace the muffler too while I am at it so I don't have to get back into the exhaust again any time soon. The only thing that worries me is the rusted bolts and nuts on the exhaust flanges from the mini-cats to the exhaust manifolds. Does anyone know if they used anti-sieze on the bolts at the factory? Any tips or tricks are very much appreciated.

Thanks.

Jimmy

 

replace the muffler

A good choice then you may not need to work on that for many many years.

Stainless steal a good choice = no rust but $$$

 

They don't use anti-sieze at the factory.

Start soaking it with Kroil or PB Blaster. Do you have a torch? By far dealing with the fasteners is the worst part of exhaust work.

 

If you have a torch torch all the pipes off that's what most shops do its way faster and way less work.

Like instant presto everything done

Or a power saw sawzall

Next the hard part installing the new system

 

I have both Kroil and PB Blaster, will soak the bolts the night before and again in the morning when I start the job. I don't have a torch but I may see if I can buy a cheap one at Harbor Freight. Down here in Florida we don't have the rust/corrosion problems like they do up North. The bolts and nuts do have a rust coat on them, but it really does not look that bad. I can still very easily see the threads on the bolts. I knew a guy once who was from Pennsylvania, he said up there you work with a wrench in one hand and a torch in the other..

Thanks.

Jimmy

 

I remember watching the shop replace all the exhaust system under my Dak it took just a few seconds he torched it all off ASAP

Cut cut cut plop done

This place made all its own bends from tubing this guy was so fast and good at what he did he made it look like fun.

He also made easy bends no restrictions or hard crimps.

Man this guy was good the guy was like some maniac he was so fast.

 

Well I bought myself a good code reader that reads live data. The scanner tells me the Bank 2 downstream O2 is switching voltage much faster than the Bank 1 downstream sensor. Bank 1 downstream is switching from .5 to .8 volts, and it changes pretty slowly. Bank 2 is going from .16 to .74 volts and switches just about at the same rate as the Bank 2 upstream sensor.

I also bought a laser pointer thermometer, it's a neat tool to have. On a 2000 RPM steady idle the inlet temp of Bank 2 cat is 350 degrees. Outlet temp is 560 degrees.

I have not had time to do any vacuum leak checks but the truck runs perfectly fine. Yesterday I passed a semi going up hill in 5th gear with the AC on and I still had some throttle left. No power loss on flat roads either, throttle response is fine. I do not smell any fumes or fuel and do not hear any exhaust leaks. I do have a 180 degree thermostat and I have been adding Marvel Mystery Oil to my gas for the last couple years, roughly 4 ounces to each 10 gallons of gas. I bought gas yesterday to check my MPG, it is down by exactly 1 MPG but that is not too far out of the ordinary. I did not add any MMO to the gas I bought yesterday.

I wonder if the 180 t-stat has something to do with this problem, but lots of us run a 18.0 t-stat and I have not heard of much cat-related codes from it. MMO is pretty mild stuff but it may have contributed to the cat failure. I was using it to help my gas mileage and as an upper cylinder lube/fuel injector cleaner. I am not smart enough to know if MMO caused this cat problem but I really do doubt it.

I found an exhaust shop, guy said he could sell me a generic universal cat for $100.00 but he needs to see the truck first to quote the labor. Is a universal cat OK? I may just pay him to install it, stop using MMO and see how it goes.

Thanks for any help. Sorry this thread is getting so long and drawn out. It's frustrating because I don't know what to look for or how to fix the problem.

Jimmy

 

A universal pre-cat should be fine. I know Magnaflow makes some but check what brand he's putting on.

My opinion on fuel additives, of any kind, don't use them on a regular basis. It all goes through the cat.

On the thermostat, I run OEM. The engine was designed to run at 195 and it'll help burn off moisture in the oil and any fuel dilution.

Just my two cents. Good luck.

 

Thanks Dan..I installed the 180 t-stat about 6 years ago. I used it and 3923's to eliminate ping. It has been OK up until now but I think it made the truck run just a little bit rich. I wonder if that has anything to do with this cat problem. I used MMO to help with gas mileage and as a UCL, but I will probably stop using it now. I don't have any MMO in my gas now and my truck is running fine. I am going to check the O2 graphs and fuel trim data when I get home from work. I hope those will tell me a lot more about what is going on with my truck.

Thanks

Jimmy

 

If your State has strong SMOG testing and you passed all the time I don't think you were running rich or you would not pass.

That is what SMOG is all about reducing smog and excess gas fumes from getting into the air.