Exhaust question - what is this pipe on top of first cat?
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Senior User
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From: Cincinnati
Exhaust question - what is this pipe on top of first cat?
I posted this in the exhaust forum, but it doesn't get much action over there...So I'll present it to a forum I'm familiar with --
I'm trying to get my '88 F250/351 ready for sale and I have an exhaust leak/problem. Here is the question:
Within the exhaust off the headers, the Y pipe goes into a single pipe, then into the first(?) cat. Attached to and above that cat, there is smaller, maybe 1" pipe that goes back up to the back of the block. Mine has rusted through where it attaches to that cat - therefore a bad exhaust leak. Will I need to replace the cat and is this an integral part to the cat, or what other options do I have? Hope I've explained good enough. I'm not good with exhausts, so direction is appreciated. Thanks,
I'm trying to get my '88 F250/351 ready for sale and I have an exhaust leak/problem. Here is the question:
Within the exhaust off the headers, the Y pipe goes into a single pipe, then into the first(?) cat. Attached to and above that cat, there is smaller, maybe 1" pipe that goes back up to the back of the block. Mine has rusted through where it attaches to that cat - therefore a bad exhaust leak. Will I need to replace the cat and is this an integral part to the cat, or what other options do I have? Hope I've explained good enough. I'm not good with exhausts, so direction is appreciated. Thanks,
Posting Guru
Joined: Jun 2004
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From: just outside of Phila.
Umm...take this and run with it, because it's an incomplete answer, but close to the right one. I just did this too and know exactly what you're talking about.
Coming out of the cat it goes up along your firewall, then I believe to the EGR? Someone once said "thermactor" to me, but it sounds like a fake name(not saying it is, it just sounds it)...well, here ya go. I'm a major Google junky....
http://home.earthlink.net/~bubbaf250/parts/parts05.html
One of the first hits. It's rare that you won't get an answer from one of the guys in here, but in the off chance that it does happen, Google may work. If you're going to do some work on it yourself, I suggest getting some opinions from the guys in here. I once asked about it before, and found out enough that I'd rather have had someone else do it.
Search in here...I know it's in here. This forum too I think.
Coming out of the cat it goes up along your firewall, then I believe to the EGR? Someone once said "thermactor" to me, but it sounds like a fake name(not saying it is, it just sounds it)...well, here ya go. I'm a major Google junky....
http://home.earthlink.net/~bubbaf250/parts/parts05.html
One of the first hits. It's rare that you won't get an answer from one of the guys in here, but in the off chance that it does happen, Google may work. If you're going to do some work on it yourself, I suggest getting some opinions from the guys in here. I once asked about it before, and found out enough that I'd rather have had someone else do it.
Search in here...I know it's in here. This forum too I think.
Hotshot
Joined: Jul 2002
Posts: 14,285
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From: Bend,OR
[QUOTE=jdmorg]
Coming out of the cat it goes up along your firewall, then I believe to the EGR?
actually that pipe runs to a cross over tube that connects to the back of each head.
any muffler shop can repair where its leaking from. finding a new pipe like that though might be difficult.
Coming out of the cat it goes up along your firewall, then I believe to the EGR?
actually that pipe runs to a cross over tube that connects to the back of each head.
any muffler shop can repair where its leaking from. finding a new pipe like that though might be difficult.
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Joined: Jul 2005
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Originally Posted by scootin
I posted this in the exhaust forum, but it doesn't get much action over there...So I'll present it to a forum I'm familiar with --
I'm trying to get my '88 F250/351 ready for sale and I have an exhaust leak/problem. Here is the question:
Within the exhaust off the headers, the Y pipe goes into a single pipe, then into the first(?) cat. Attached to and above that cat, there is smaller, maybe 1" pipe that goes back up to the back of the block. Mine has rusted through where it attaches to that cat - therefore a bad exhaust leak. Will I need to replace the cat and is this an integral part to the cat, or what other options do I have? Hope I've explained good enough. I'm not good with exhausts, so direction is appreciated. Thanks,
I'm trying to get my '88 F250/351 ready for sale and I have an exhaust leak/problem. Here is the question:
Within the exhaust off the headers, the Y pipe goes into a single pipe, then into the first(?) cat. Attached to and above that cat, there is smaller, maybe 1" pipe that goes back up to the back of the block. Mine has rusted through where it attaches to that cat - therefore a bad exhaust leak. Will I need to replace the cat and is this an integral part to the cat, or what other options do I have? Hope I've explained good enough. I'm not good with exhausts, so direction is appreciated. Thanks,
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Lead Driver
Joined: Sep 2002
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From: Gateway to the West
Slickerthanyou has it right on the money. The tube SHOULD have a metal check valve at the top and a formed rubber hose from there back to the Thermactor air diverter valve near the back of the passenger side cylinder head. Without this connected to the Thermactor system, the catalytic converter will NEVER heat up to the proper operating temperature and will render the CAT useless. As already stated, this will cause an automatic failure during an emissions test. The diverter valve splits the fresh air being pumped from the Thermactor (smog) pump to the air injection ports in the heads and the catalytic converter. Removing the air injection to the heads WILL mess with your O2 sensor readings which will in turn effect computer tuning and fuel mileage.
Last edited by greystreak92; Sep 7, 2005 at 05:28 PM.
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Posting Guru
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From: just outside of Phila.
Originally Posted by Kemicalburns
Finding a new pipe like that though might be difficult.
Originally Posted by Greystreak92
Removing the air injection to the heads WILL mess with your O2 sensor readings which will in turn effect computer tuning and fuel mileage.
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Senior User
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From: Cincinnati
Thanks for the responses. That sounds like my problem - it is rusted right where it goes into the cat. If I have a shop replace that cat, any idea of cost? I need it to be able to pass emmissions in order to sell easier, so need it legal. Other options?
Lead Driver
Joined: Sep 2002
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From: Gateway to the West
If the check valve is still intact, and there is enough of the metal tube extending from the cat after you cut away the rusted section, you can buy a chunk of hi-temp "emissions" hose to run between the bottom of the check valve and the tube from the cat. Now it MUST be "emissions" hose because of the extreme temps involved but its available at most parts suppliers. Its not cheap. I think $7-8 per foot but even if you need two feet of it its still cheaper than replacing the entire cat just because the air injection tube rusted. A length of that hose and two clamps and you are back in business.
Elder User
Joined: Apr 2002
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From: NJ
actually there is also another purpose for injecting air into the cat.
the catalytic converter burns the unburned fuel left in the exhaust gasses. the air is injected into the cat to help this unburned fuel burn up in the cat. with out the air the cat will not get hot enough to burn this completely and will eventually plug.
the catalytic converter burns the unburned fuel left in the exhaust gasses. the air is injected into the cat to help this unburned fuel burn up in the cat. with out the air the cat will not get hot enough to burn this completely and will eventually plug.
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Originally Posted by BOJOFASO
actually there is also another purpose for injecting air into the cat.
the catalytic converter burns the unburned fuel left in the exhaust gasses. the air is injected into the cat to help this unburned fuel burn up in the cat. with out the air the cat will not get hot enough to burn this completely and will eventually plug.
the catalytic converter burns the unburned fuel left in the exhaust gasses. the air is injected into the cat to help this unburned fuel burn up in the cat. with out the air the cat will not get hot enough to burn this completely and will eventually plug.
Lead Driver
Joined: Sep 2002
Posts: 9,182
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From: Gateway to the West
Originally Posted by BOJOFASO
actually there is also another purpose for injecting air into the cat.
the catalytic converter burns the unburned fuel left in the exhaust gasses. the air is injected into the cat to help this unburned fuel burn up in the cat. with out the air the cat will not get hot enough to burn this completely and will eventually plug.
the catalytic converter burns the unburned fuel left in the exhaust gasses. the air is injected into the cat to help this unburned fuel burn up in the cat. with out the air the cat will not get hot enough to burn this completely and will eventually plug.