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Old 12-11-2013, 02:44 PM   #1
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Workhorse 8.1 Exhaust Muffler

Hi Guys----I was redirected to this forum so here goes----On each of my mufflers I have a metal cover with insulation wrapped around the muffler. The drivers side was rusted so badly due to condensation that I removed both the metal and insulation, The muffler is in good condition but I am concerned that there may be to much heat under the coach floor now. Do I re install the insulation and cover or maybe install a heat shield?

Any help would be greatly appreciated

Pitbull
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Old 12-12-2013, 09:20 AM   #2
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On mine, the metal cover over the "insulation" is tack welded to the muffler at several places. I've only partially removed the rusty cover and insulation along the bottom of each muffler. IF the entire cover is removed from the muffler, I would have some concern about too much heat radiating up towards the coach above and try to fashion some sort of heat shield to protect the underside of the coach.
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Old 12-12-2013, 10:16 AM   #3
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What lies directly above each muffler and how much space is there? Fabricating and installing a heat shield above the muffler shouldn't be a tough job.
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Old 12-12-2013, 10:34 PM   #4
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Lots of those mufflers are being replaced with more common and cheaper (and a litle noisier) mufflers without heatshields, apparently without any problems.
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Old 12-13-2013, 01:59 PM   #5
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I will measure the clearance and put it on the thread. My mufflers are installed vertical instead of flat -- if that makes any sense to anyone. So the top will be closer to the floor than if it was installed flat like a conventional install. Maybe this is just on 2008's ?
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Old 12-15-2013, 04:23 PM   #6
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Check out this solution from ALLDATA

SOLVING GM HEAT SHIELD NOISE IS A “SNAP”
By Ed Dorowski, ALLDATA Editor
and Jeff Webster, ALLDATA Technical writer

CONDITION: Some General Motors truck owners may comment on a popping/snapping noise from under the vehicle at idle or immediately after the vehicle is shut off. Some popping/snapping noise from the exhaust system during cool down is a normal condition. The noise may be intermittent depending on the outside temperature and or temperature of the exhaust system at the time of testing.

CAUSE: As the exhaust system warms and cools, the muffler and the muffler heat shield expand and contract at different rates and may cause a popping and/or snapping noise. Some noise from the exhaust system during cool down is a normal condition. The vehicle owner should be made aware that this service procedure is designed to reduce but not eliminate all exhaust system popping and snapping during cool down.

To correct the condition, replace the muffler heat shield following the steps in this Tech Tip.

Applicable Models

2002-2006 Cadillac Escalade, Escalade EXT
2003–2006 Cadillac Escalade ESV
2002–2006 Chevrolet Avalanche, Suburban, Tahoe, Silverado, Silverado HD
2007 Chevrolet Silverado Classic, Silverado HD Classic
2002–2006 GMC Sierra, Sierra HD , Yukon, Yukon Denali, Yukon Denali XL
2007 GMC Sierra Classic, Sierra HD Classic
2003–2006 HUMMER H2

Vehicles with 4.8L, 5.3L, 6.0L or 8.1L Gasoline Engine (VINs V, B, T, Z, N, V, G – RPOs LR4, L33, LM7, L59, LQ9, LQ4, L18)

IMPORTANT: This Repair/Service Procedure is excerpted from a Technical Service Bulletin published by the vehicle manufacturer, and is intended for use by trained, professional technicians with the knowledge, tools and equipment to do the job properly and safely. It is recommended that this procedure not be performed by “do-it-yourselfers.”

Parts Information

PART # ENGINE / MODEL DESCRIPTION QTY
15253526 4.8L or 5.3L engine, 1500 Series Base Utility Trucks ONLY Muffler Heat Shield – 24-inch 1
10393433 6.0L engine (LQ4, LQ9) H2 or 1500 Series Luxury Utility Trucks ONLY Muffler Heat Shield – 28-inch 1
15808181 6.0L or 8.1L engine (LQ4, LQ9, L18) 2500 Series Utility, HD Pickups and Luxury Pickup Trucks ONLY Muffler Heat Shield – 25-inch 1
15103174 6.0L or 8.1L engines ONLY Clamp, Exhaust Pipe 1
10391259 All Vehicles Strap, Muffler Heat Shield 3
15103184 25 Series Suburban/Avalanche and 8600 lb. 25 Series Pickups w/LQ4) Clamp, Exhaust Pipe – 2.75″ pipe 3
15102680 25 & 35 HD Pickups w/LQ4 or L18 engines Clamp, Exhaust Pipe – 3″ pipe 3
Correction

Review safety procedures in ALLDATA Repair before beginning.

DO THIS DON’T DO THIS
Install a new heat shield and straps on the existing muffler. DO NOT replace the exhaust system components other than the muffler heat shield.
Raise and support the vehicle using factory and/or industry standard approved practices.

In order to avoid being burned, do not service the exhaust system while it is still hot. Service the system when it is cool.

Always wear protective goggles and gloves when removing exhaust parts as falling rust and sharp edges could result in serious personal injury.

Remove the nuts securing the muffler to the catalytic converter.

On 6.0L and 8.1L equipped vehicles only, loosen the exhaust pipe clamp.
Do not use oil base lubricants on the rubber exhaust hangers.

Apply a soapy solution to the exhaust pipe hanger rods in order to ease the removal of the exhaust hangers.

Pry the exhaust hangers free from the exhaust pipe hanger rods.

It is not necessary to remove the muffler from the vehicle to replace the muffler heat shield.

Reposition the muffler to gain access to the muffler heat shield.

Use extreme caution not to damage the muffler when removing the heat shield from the muffler.



Using an air-powered hack saw blade, or equivalent, cut off the existing muffler heat shield just as the heat shield rises off of the muffler (Figure 1).

Remove the heat shield from the muffler.

Hammer flush the remaining heat shield to the muffler (Figure 2).

The new heat shield should not come in contact with the remaining muffler heat shield. The new heat shield should not come in contact with the horizontal lock seam on the muffler.



Install the new heat shield (see parts information) onto the muffler (Figure 3).

Install three straps, P/N 10391259, so that the strap screw head will be located on top of the muffler.

Tighten the strap screw to 35 lb in (4 N.m).

Cut off the excess strap material and bend the strap over the strap screw head (Figure 4).

Remove the exhaust pipe clamp.

ONLY 6.0L and 8.1L equipped vehicles require a new exhaust pipe clamp, P/N 15103174.

On 6.0L and 8.1L equipped vehicles only, install a new exhaust pipe clamp, P/N 15103174, on the exhaust pipe.

Reposition the muffler in the correct position.

Slide the muffler forward into position, aligning the studs with the rear of the catalytic converter.

Install the nuts securing the muffler to the catalytic converter, but DO NOT tighten at this time.

Apply a soapy solution to these areas in order to ease the installation of the hangers:

The inner diameter of the exhaust pipe hanger
The exhaust pipe hanger rod
Press the exhaust pipe hangers over the exhaust pipe hanger rods.

Tighten the muffler nuts by hand until each contacts the metal flange.

Tighten the muffler nuts to 33 lb ft (45 N.m).

On 6.0L and 8.1L equipped vehicles only, tighten the exhaust clamp to 36 lb ft (50 N.m).

Lower the vehicle and test drive it to confirm the repair.

Authors: Ed Dorowski has 19 years of Domestic and Import dealership and independent shop experience as a service consultant, ASE Certified Master Technician, Nissan® Certified Master Technician, & California Smog Test & Repair Technician. Jeff Webster has 20 years of experience as a writer/editor.

GM, General Motors, Cadillac, Escalade, Escalade EXT, Escalade ESV, Chevrolet, Avalanche, Suburban, Tahoe, Silverado, Silverado HD, Silverado Classic, Silverado HD Classic, GMC, Sierra, Sierra HD, Yukon, Yukon Denali, Yukon Denali XL, Sierra Classic, Sierra HD Classic and HUMMER H2 are registered trademark names and model designations of General Motors Corporation. Nissan is a registered trademark of Nissan Motor Co. Ltd. All trademark names and model designations are being used solely for reference and application purposes.

11/05/2009

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Old 12-15-2013, 05:11 PM   #7
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Flanagan, nice article for a pick up, SUV, or van with a creaking exhaust system. A heat shield is a piece of metal blocking heat radiating from the exhaust so it doesn't bake the underside of the vehicle. On the OP's RV I'll wait until he scopes out distances and what's above or close to the exhaust. Some of the 'pearls of wisdom' in this how to: "do not service the exhaust system while it is still hot. Service the system when it is cool." Only replace shields, not pipes or mufflers? Why?? A couple of pieces of stiff aluminum sheet metal can be fabricated to form a shield for heat. If possible, I'd fasten it to the underside of the RV rather than clamp it on the muffler or pipes, resulting in the creaking and rattling cited in your contribution. No need to add weight to the exhaust system to strain the hangers, and clamping aluminum to steel is going to create electrolysis that will be problems down the road. Wrapping a muffler with insulation and metal originally also was a recipe for failure, the insulation traps road salt and moisture (when cool) against the muffler and means Midas gets the gold. Speaking of gold, I wonder what the cost of all those parts add up to??
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Old 12-15-2013, 05:27 PM   #8
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Quote:
Originally Posted by BFlinn181 View Post
Flanagan, nice article for a pick up, SUV, or van with a creaking exhaust system. A heat shield is a piece of metal blocking heat radiating from the exhaust so it doesn't bake the underside of the vehicle. On the OP's RV I'll wait until he scopes out distances and what's above or close to the exhaust. Some of the 'pearls of wisdom' in this how to: "do not service the exhaust system while it is still hot. Service the system when it is cool." Only replace shields, not pipes or mufflers? Why?? A couple of pieces of stiff aluminum sheet metal can be fabricated to form a shield for heat. If possible, I'd fasten it to the underside of the RV rather than clamp it on the muffler or pipes, resulting in the creaking and rattling cited in your contribution. No need to add weight to the exhaust system to strain the hangers, and clamping aluminum to steel is going to create electrolysis that will be problems down the road. Wrapping a muffler with insulation and metal originally also was a recipe for failure, the insulation traps road salt and moisture (when cool) against the muffler and means Midas gets the gold. Speaking of gold, I wonder what the cost of all those parts add up to??
BFinn, my take away was that GM recognized there was a problem and this article gives step by step methodology for removal of the corroded heat shield. What you do from there to mitigate the heat is up to you. I was pleased to learn that my mufflers were intact so expensive replacement is averted for now : )
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Old 12-19-2013, 08:25 PM   #9
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The exhaust system on our motorhome chassis were designed by Workhorse engineers and GM provides little guidance on 2.5" systems that are 30 feet long. I don't have heat shields on my rig, never did. Does the floor gets warm, yes it does. After a day's run the residual heat in the floor needs time to dissipate.

My mufflers are over 10 years (~99,750 + miles) old and are still viable with no holes. (yet) I don't expect that they'll last forever but when they go I'll be looking for a workable solution.
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Old 12-21-2013, 11:27 AM   #10
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Hi Guys---Sorry I have been away------I measured my clearance and it is 7 inches from the house deck-----I spoke with a exhaust shop fellow that has 30 years experience that said they are O.E.M. mufflers and he would not worry about the insulated skin coming off. He said to get in your motorhome and go to Florida--ha ha.
It is his opinion----I just like to talk to RVers because they have the real life experiences on the road.
I am going to measure what is directly above but I believe it is just vinyl flooring.

Pitbull
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