Our 2005 Tiffin Allegro has the GMC 8.1 on the workhorse chassis. It's got 58,000 miles on it. We've had it for 6 years. Last year we replaced the transmission cooler assembly (rusted out) this year we replaced the oil pump and had to replace all the brake rotors and pads etc.due to rust.We're feeling although it was expensive we should have a pretty sound rig and plan to keep it.Today while trying to repair the Kwickie (sp) steps I noticed a piece of rusted outer layer of sheet metal hanging off one of the mufflers.I'm not sure how expensive mufflers are but it appears that they'd have to be cut off etc. IE not a DIY job. Are there many layers of metal on a muffler? I'm wondering if wrapping the rusted one with sheet metal would help it last a bit longer before having to replace it - - or probably both of them. Hope this doesn't sound too silly. I'm just a bit bummed.

Many mufflers have had their lives extended by wrapping them with sheet metal. The problem is that since you seem to have a rust problem in your area, the inside muffler baffles can also rust and break loose. When this happens it can increase the back pressure in the muffler which can cause poor performance/fuel mileage and may eventually cause engine damage.

rgatijnet1 wrote:Many mufflers have had their lives extended by wrapping them with sheet metal. The problem is that since you seem to have a rust problem in your area, the inside muffler baffles can also rust and break loose. When this happens it can increase the back pressure in the muffler which can cause poor performance/fuel mileage and may eventually cause engine damage.Thanks for your reply. The service center used an analyzer to diagnose the oil pump problem. Would that have shown them a back pressure problem etc?

I would go ahead and replace the mufflers with Monroe stainless ones and be done with it. I'm trying to figure why you would have needed a oil pump with low mileage. WH rep that came to my shop during our brake issues told me the 8.1 would get as low as 3 to 6 psi idling while hot. I had a hard time with that one but he swore it was true.

you spend money to upkeep it but the one thing that can cause carbon monoxide poisoning you want to patch:h

Bird Freak wrote:I would go ahead and replace the mufflers with Monroe stainless ones and be done with it. I'm trying to figure why you would have needed a oil pump with low mileage. WH rep that came to my shop during our brake issues told me the 8.1 would get as low as 3 to 6 psi idling while hot. I had a hard time with that one but he swore it was true.Yes, I was concerned.The problem wasn't just low idle pressure. The oil pressure dropped while on the highway. However more than one service center indicated that the oil pump was a problem on some of those engines. I'm thankful that the problem finally occurred while diagnosing. It was our third attempt.

Catalytic converters for 2005 workhorse with GMC 8.1 vortec

Hank_MI
Explorer
Aug 15, 2015
TimfmCT wrote:
Hank MI wrote:
Thread title says catalytic converter, then you say muffler. Many converters have a separate heat shield attached to them, they got really hot. Could the hanging metal be the heat shield?

Good point, Hank. It is the muffler that is peeling on the bottom. Little did I know how small the converter is.

Okay, just checking. We have an 03 Winnebago on the Workhorse chassis and the exhaust system is in great shape.
DSDP_Don
Explorer
Aug 14, 2015
Tim....Don't mess with a disintegrating muffler. The carbon monoxide poisoning will slowly overtake you without you even knowing it.

You don't need anything fancy. Find a truck shop that does mufflers and have them install a generic muffler.
TimfmCT
Explorer
Aug 14, 2015
Hank MI wrote:
Thread title says catalytic converter, then you say muffler. Many converters have a separate heat shield attached to them, they got really hot. Could the hanging metal be the heat shield?

Good point, Hank. It is the muffler that is peeling on the bottom. Little did I know how small the converter is.
rgatijnet1
Explorer III
Aug 14, 2015
Bird Freak wrote:
I would go ahead and replace the mufflers with Monroe stainless ones and be done with it.
I'm trying to figure why you would have needed a oil pump with low mileage. WH rep that came to my shop during our brake issues told me the 8.1 would get as low as 3 to 6 psi idling while hot. I had a hard time with that one but he swore it was true.

I have an 8.1L engine and I keep the OBDII sensor hooked up at all times to monitor certain engine functions. At idle my oil pressure is running 19-21psi and at 2200 rpm cruise down the highway 44-46 psi.
Like any other component, I guess the oil pump could have failed but I think I would get a second opinion.

I should add that if the OP has the Actia dash on his coach they can be programmed to give you the oil pressure at all times.
Hank_MI
Explorer
Aug 14, 2015
Thread title says catalytic converter, then you say muffler. Many converters have a separate heat shield attached to them, they got really hot. Could the hanging metal be the heat shield?
TimfmCT
Explorer
Aug 13, 2015
newman fulltimer wrote:
you spend money to upkeep it but the one thing that can cause carbon monoxide poisoning you want to patch:h

Yes, you make a good point ...... if the muffler was "leaking" IE: making noise, I'd certainly make R&R of them a higher priority.
TimfmCT
Explorer
Aug 13, 2015
Bird Freak wrote:
I would go ahead and replace the mufflers with Monroe stainless ones and be done with it.
I'm trying to figure why you would have needed a oil pump with low mileage. WH rep that came to my shop during our brake issues told me the 8.1 would get as low as 3 to 6 psi idling while hot. I had a hard time with that one but he swore it was true.

Yes, I was concerned.The problem wasn't just low idle pressure. The oil pressure dropped while on the highway. However more than one service center indicated that the oil pump was a problem on some of those engines. I'm thankful that the problem finally occurred while diagnosing. It was our third attempt.
newman_fulltime
Explorer II
Aug 12, 2015
you spend money to upkeep it but the one thing that can cause carbon monoxide poisoning you want to patch:h
Bird_Freak
Explorer II
Aug 12, 2015
I would go ahead and replace the mufflers with Monroe stainless ones and be done with it.
I'm trying to figure why you would have needed a oil pump with low mileage. WH rep that came to my shop during our brake issues told me the 8.1 would get as low as 3 to 6 psi idling while hot. I had a hard time with that one but he swore it was true.
TimfmCT
Explorer
Aug 12, 2015
rgatijnet1 wrote:
Many mufflers have had their lives extended by wrapping them with sheet metal. The problem is that since you seem to have a rust problem in your area, the inside muffler baffles can also rust and break loose. When this happens it can increase the back pressure in the muffler which can cause poor performance/fuel mileage and may eventually cause engine damage.

Thanks for your reply. The service center used an analyzer to diagnose the oil pump problem. Would that have shown them a back pressure problem etc?

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Catalytic converters for 2005 workhorse with GMC 8.1 vortec

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