Catalytic converter overheating?

[dttruax]

Was bringing my car home from my mechanic (details why in this other thread Radiator fan turns on more often/sometimes won't turn off). Drove it for a few miles. Got about a mile or so from my house and the check engine light came on. Turned right around and took it back to my mechanic to have him check it out today.

Called me back morning. He said that the catalytic converter was overheating/operating inefficiently (figure that's what was causing the hot burning smell coming from the engine bay and under car that I thought was maybe the gear box and/or clutch). Don't know exactly what code came up and I forgot to ask. He said after talking with Subaru, it's the "front" CC (apparently that's the only one of the 3 CC's that is monitored in any way). Parts + labor ~ $900 .

I'm wondering if the catalytic converter overheating is what is causing the engine to run a little warmer than usual and causing the radiator fans to come on high more often, especially after driving awhile and/or at speed (60 mph @ ~2500 rpm) that I asked about in my other thread. My mechanic said he doesn't think so, but I'm not sure where all the CC's are and all. Any insight would be helpful.

2004 WRX. 137,000 miles. No mods.

[MainFrame]

The uppipe catalytic converter is a liability, the best thing to do is to remove it and use the resistor fix for the EGT sensor. That's the first thing that should be done to any 2L WRX, and honestly, I wouldn't drive a car with it in there. Not only does it hinder performance, there are multiple accounts of it failing and destroying the turbo. If I were you I would either gut it, or look for a used 2.5L uppipe to replace it with. It can be the source of many problems and replacing it with another catted uppipe just doesn't make sense.

[Obeisance]

If you get your uppipe (with the catalytic converter) removed and it's not too much trouble, could you please take some good pictures of the catalytic converter? I've read a number of threads which suggest that switching to a catless uppipe is a good first mod because it removes the possibility of the cat material entering the turbo if it breaks up. I'm curious to see the condition of yours.

I have no guesses for you about the cat causing overheating, but I think I've heard before that the function of catalytic converters degrades quite a bit at higher temperatures or in lots of unburnt fuel because of carbon reactions/buildup. This overheating and cat clogging may be indicative of another problem.

[UEDan]

My uppipe was clogged at 100k. Wouldn't be surprised if it failed.
And my radiator fans stay on for a while after turning off the engine. I can listen to a few songs before they turn off. No overheating, rock solid temp gauge.

[SKI.WRX]

Someone who isn't me removed a cat from an 02 wrx up-pipe at 105,000 miles and it was functioning perfectly and intact (before a drill bit and screwdriver chewed it up). However, who is to say that the next WOT event wouldn't have shredded it grenading the turbo and likely damaging the post turbo cat/s with it.

Overheating cat likely means High EGT's or the cat is clogged no allowing heat to escape efficiently through the exhaust. Higher EGT means Higher water temp which can mean the fans come on in an attempt to reduce temps but that is purely a guess. Start with getting rid of the cat then reassess.

[dttruax]

Overheating cat likely means High EGT's or the cat is clogged no allowing heat to escape efficiently through the exhaust. Higher EGT means Higher water temp which can mean the fans come on in an attempt to reduce temps but that is purely a guess. Start with getting rid of the cat then reassess.

That's what I was getting at when I quizzed my mechanic on exactly which converter was bad and caused the CEL because I knew that there was a CC in the up-pipe. If that was overheating/clogged, etc., I was thinking that maybe that would be causing "hotter air" being forced into the engine which could be causing the higher coolant temps which would cause the radiator fans to come on more often, especially at speed and/or when some boost was applied after the engine came up to temperature. As I said in my other post, the engine hasn't shown any signs of overheating, so I guess the cooling system has been working as it should even with the increased temps. But as you said, that's purely speculation on my part; I'll find out more once it's replaced. Also, as far as I can tell, the turbo has been working fine as well. I don't have a boost gauge and don't drive it all that hard, so it's hard to tell sometimes.

But, is the "front" catalytic converter the one in the up-pipe or another one? I would speculate that it would be since I was told only 1 catalytic converter is being monitored and if you wanted to monitor any of them, that would be the one to give you a heads-up before any potential damage to the turbo.

[Mikie13]

Yeah, replace with catless UP for $200 or so, and do the resistor fix for the CEL. Do not pay $900+ to have it "properly fixed" by a mechanic.

[EJ257]

But, is the "front" catalytic converter the one in the up-pipe or another one? I would speculate that it would be since I was told only 1 catalytic converter is being monitored and if you wanted to monitor any of them, that would be the one to give you a heads-up before any potential damage to the turbo.

The "front CC" is a reference to the pre-turbo cat, which is in the uppipe. Labor rate is going to be 3-4 hours to replace it. It wouldn't surprise me if the factory part is $500-600, considering we're dealing with a CC.

Get an aftermarket unit (e.g., Grimmspeed or TurboXS) for ~$150, new gaskets, and invite a friend or two over to help with the install and finish the beer/pizza you buy for the day.

[dttruax]

My uppipe was clogged at 100k. Wouldn't be surprised if it failed.
And my radiator fans stay on for a while after turning off the engine. I can listen to a few songs before they turn off. No overheating, rock solid temp gauge.

The fans turn off when the engine is turned off.... but they tend to come on more often now (even driving in temps in the 30's or 40's) and seem to go to high speed when driving st speed (50-60+ mph... hard to hear sometimes, but at times you can hear them go from high to low after coming to a stop sign, etc.) and take longer to turn off at idle. But my mechanic said they tested everything and that the fans came on at the correct coolant temp and turned off when they should... or course I think that testing was done with the car idling, and not while driving.... and the rest of the cooling system was tested a few months ago when I had to get the radiator replaced.

[dttruax]

The "front CC" is a reference to the pre-turbo cat, which is in the uppipe. Labor rate is going to be 3-4 hours to replace it. It wouldn't surprise me if the factory part is $500-600, considering we're dealing with a CC.

Get an aftermarket unit (e.g., Grimmspeed or TurboXS) for ~$150, new gaskets, and invite a friend or two over to help with the install and finish the beer/pizza you buy for the day.

This makes me a little more confident that fixing the converter problem will also fix the radiator fan issue (crossing fingers).

I wish I had the aptitude/equipment/time to do something like that myself..... Although after this expense, I think I will try to replace my starter by myself since it doesn't seem that bad... I just need to find a good tutorial on how to remove the intercooler

[EJ257]

This makes me a little more confident that fixing the converter problem will also fix the radiator fan issue (crossing fingers).

I wish I had the aptitude/equipment/time to do something like that myself..... Although after this expense, I think I will try to replace my starter by myself since it doesn't seem that bad... I just need to find a good tutorial on how to remove the intercooler

See if they would be willing to replace the uppipe with a catless unit. Most non-performance shops won't tamper with ECDs, however. How close are you to Alpharetta? Top Speed Motorsports is there, and does a lot of work on Subarus. Would be worth a trip there, if your mechanic won't do a catless install...

[SD_GR]

Also, again, you will need a resistor fix if going catless or the CEL will not go away.

[dttruax]

Just doing a quick parts search. Which part needs to be replaced?

http://subarupartsforyou.com/cp_part...nly+&year=2004

[dttruax]

I have no guesses for you about the cat causing overheating, but I think I've heard before that the function of catalytic converters degrades quite a bit at higher temperatures or in lots of unburnt fuel because of carbon reactions/buildup. This overheating and cat clogging may be indicative of another problem.

Was wondering the same thing.... maybe just because the car is 9 years old and has 137,000 miles on it. I don't know much about the newer converters, but I know that the older ones in particular didn't last forever.

[SD_GR]

Which part needs to be replaced?

On my phone the link won't load. However, because it's a lot of work to change the up pipe I recommend the question be reversed: you tell us the part that had failed. A "square" mechanic may not know what the "up pipe" is.

Are you sure it's the up pipe? Just checking to save headaches, not trying to be a pain.