I have a Kohler Command Pro 30 V twin engine. We have just replaced the exhaust, including muffler and pipes and when we run it for a few minutes the exhaust system was glowing red hot. Is this normal

Do people hear your vehicle coming down the street before they can actually see it? This can be an embarrassing situation. A muffler that is suddenly noisy is often caused by the driver hitting something while on the road, damaging the exhaust system. Rust can also be a culprit of holes in the muffler, resulting in a noisy muffler which gets progressively worse as the holes get bigger.
Exhaust systems in newer vehicles may now last well over 100,000 miles without causing any concerns. But because the exhaust system is exposed to the conditions of the road, damage may occur without warning. The parts of the exhaust system that can be damaged include:

• Manifold
• Pre-catalytic converter
• Front pipe
• Catalytic converter
• Intermediate exhaust pipe
• Front muffler
• Rear exhaust pipe
• Rear Muffler

If you do hear a loud noise and you suspect it is the exhaust system, be sure to keep fresh air coming into the vehicle and don't sit in the car while it's idling. If there is a leak, carbon monoxide, a toxic gas, can get into the interior of the car. There is no distinguishing odor so it is easy to be overcome by it.
In order for your vehicle to keep running smoothly, all of its components need to be in good working order. Taking the time for regular car inspections and keeping up with needed repairs is the best way to ensure that everything is working as it should. This inspection should include the exhaust system.
"Why is my muffler so loud?" For an answer to your question, contact our ASE Certified technicians at Dependable Car Care for more information and to schedule an inspection of your exhaust system. Our auto shop proudly serves residents in the community of Ventura, CA, and the surrounding area.

Sounds like you may have a blown head gasket

Ron, A lot of cars and trucks experience this,Is your engine running good and tuned up, if you find no exhaust leak(including around the manifolds) and know baffles in mufflers are OK and not loose, you may have to consider it normal. I have not done it, some say to install an H or X pipe ahead of mufflers to equalize exhaust pressure and get rid of noise. Check the attached links,instruction and guides, Good luck
"I hope this helped you out, if so let me know by pressing the helpful button. Check out some of my other posts if you need more tips and info."
http://www.fullsizechevy.com/forum/general-discussion/performance/exhaust/467084-fluttering-flapping-noise-out-exhaust.html
How After Market Exhaust Systems Can Disrupt Your Car Power Curve Exhaust...
http://www.camaro5.com/forums/showthread.php?t=269259

You can cut out the Y pipe and replace it with a flex pipe from parts store, then clamp each end of the flex pipe, the pipe diameter will be 1-7/8 or 2 inch, also for the pipe replacement piece would work from a sunfire or cavalier from 1995 and up, might need to replace the muffler strap too. as it can break from rusting, if not already rusted and broken.

your cat is plugged remove it and replace with straight pipe or replace cat

well it is located right below your motor
there are 2 places you can get the pipe from 1 is scrap or salvage the other is the dealer
it is likely you will havew to buy a new pipe from the dealer as the ones in the salvage yard are usualy crushed by machinery picking the cars up and them being droped in the mud
the only othere option is to have a muffler shop build you a dual exhaust witch might be cheeper in the long run and also allow you to get better fuel econamy and more power from the engine for towing if required take a look at the options and get a few quotes from local shops

Yes you can obtain the parts from after market. The Flex Pipe is installed on all cars hows engine is built in transverse. if you accelerate the engine tries to turn against the crankshaft rotation. W/o flex pipe your exhaust will be broken after a couple of minutes. The flex pipe acts like an accordion and eliminates this small "turns".

If the noise sounds like your muffler, but isn't coming from the area of your muffler, then you have an exhaust leak upstream from the muffler.

From the front of your muffler, follow the tubing forward to the catalytic converter, then forward to the engine exhaust manifold.

If you start with the car sitting for a few hours to make sure it's cold, you can use your hand to feel for blowing leaks while the engine is running, but chances are you'll be able to hear it. be careful of the catalytic converter itself, as it heats up fast, so check that first.

Once you've found the leak, the fix depends on the emissions laws in your state. If you have none, and the leak is in the middle of the pipe, you can buy pipe patchers (metal preferred) through auto parts stores or catalogs/websites. If you have strict emissions laws, or the leak is at the junction of the catalytic converter and pipe, you'll need to replace the failing part.

Check the heat shield on the Catalytic Converter, after a few years they start to rust off and rattle. Crawl under the Pathfinder and bang along the Converter and muffler area and see where it's coming from.   Good chances are, it's from the heat shield since you already had everything changed from the Cat back.
Good luck and hope this helps.

Sounds like you may have gotten some debris in your exhaust pipe or something was clogging your muffler. Maybe the innerds of you Catalytic Coverter went and got stuck or the innerds of your muffler gave out. That would be the only few things I could think of to cause something like that.

Sincerely,

JC