Home » Public Forums » GMCnet » Replacing the exhaust Pipe - final report
| Replacing the exhaust Pipe - final report [message #319553] |
Sun, 25 June 2017 14:44  |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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Well, It only took four days longer than I hoped.
Needed:
10' of 2-1/2" straight exhaust pipe for a 23, 13' for a 26 (an extrapolation)
2' of 3" to make new support sleeves
2- Minimum 2-1/2" clamps (I ended up needing 5)
Probably an new tail pipe can be made up by any local shop. (We had a replacement made in Omaha a while back.)
A pipe expander to fit at least 2-1/2" (The HF one is adequate.)
Sawzall with 5" metal cutting blade
Safety goggles (not just glasses - there will be chips raining on your face.)
Hearing protection (unless yours is currently unsalvageable)
Of course the standard box of hammers and wrenches.
If the old pipe does not just slide out (Mine didn't) give it up. I really wanted to get the pipe out intact, that way I could use it to mount the new support tubes in the correct places. But, sometimes and one has to go with a Plan B. \
If you have the coach high enough to side under it (my slide height is not as small as it once was), you can probably bring the Sawzall to bear and not do any collateral damage. This is why you need the 5' blade. A 3" will hang up inside the pipe and bend or break and the longer blade means you will probably do damage to surrounding parts.
Cut the exhaust pipe just forward of the rear support and just behind the forward support. This way you can wrestle the short piece out, then slide the long piece out. If the lead piece does not come out of the Y-pipe, you may be in for a fight. If I had better conditions and could have dared use a torch (next to the fuel tanks), I could have been done much sooner. A 26 has an advantage there as you don't have a fuel tank right there.
If you can't get the remaining exhaust pipe out of the Y-pipe, then cut again about 3" forward of the support sleeve.
!!Important!! If you make this cut and the pipe springs so that the cut pieces are not aligned, be ready for a fight.
To remove the remaining exhaust pipe from the Y-pipe coupling, none of my standard methods worked. I didn't have swinging room for regular chisel and I could not get enough life out of a die grinder point of make it weak enough to collapse because of the length of the engaged piece. I got a new muffler cutter for my air chisel but it could not be controlled well enough to not risk damage to the Y-pipe's coupler. As a last but final resort, I looked to my panel cutter. If you don't know what this is, it is an air chisel tool that looks a lot like three fingers with the center set back from the others. I ground the center down so it was only about 0.080 taller than the outer two and then radiused the outer two to be close to the 2-1/2. After I cut the remaining exhaust pipe close to the coupling of the Y-pipe, I was able to use the modified tool to cut the inside pipe enough for it to release. Sometimes. Plan B isn't all bad.
My Y-Pipe is an independently fabricated part and I did not discover this issue until later. If when you cut the exhaust pipe it does come out of line, then the new pipe will not go home in the coupling of the Y-pipe. I had no means that I could bring to bear that could bend the Y-pipe effectively. Even though the finally resized (with the expander mentioned above) coupling was a correct and would accept a piece of 2-1/2, I could not get it to make the desired engagement of the new exhaust pipe with the pipe in place. To this end, I went with the engagement I could get and used a strap clamp at that joint. Time will tell.
I made new support sleeves from 3" as that is what fits the existing supports. I cut pieces 9" long and then marked and drilled holes (8 at each end about ½ apart) to end the cuts that I had to make to create four 1~1-1/2" long fingers on each end. This was more work for the saw. I did think about using either the torch (long clean up) or the bandsaw, but I could not get the pipe into good position to make any of the cuts. The end fingers were prebent to make the close to the 2-1/2 diameter. I had hoped to weld the support sleeves to the exhaust pipe but not having the complete piece kind of shot that plan. I could see by the wear on the old support sleeves that the location was at least a little critical. So, on to Plan C...
So, I slid the support sleeves into the bearings. Then slid the length of exhaust pipe into place. Now began the fight to get it engaged with the Y-pipe. This was when I discovered how important the mis-alignment that I mention above really was. I was able to block and jam and wedge the Y round enough to get the exhaust started in, but only with great effort could I even get an inch of engagement. It was in there hard. I decided to go with a strap clamp on that joint.
This caused a welcome break, I went to a local shop and bought a strap clamp. I rolled the strap clamp to size and then realized that I could not assemble it in place. So, I had to pull the exhaust pipe back about a foot. It didn't pull back any easier than it went in. This caused another realization. This 2-1/2 strap clamp barely fit over the 2-1/2 pipe, there was no possibility I could get it over the coupler of the Y pipe. Back to the store. That was what they had. So I got 4 more regular clamps for the Plan C ends of the support sleeves and went to the next closest shop for another try at a strap clamp. Theirs fit over the couplers at the end of some pipe that they had.
So, back home, I put the assembled strap clamp over the exhaust pipe and wrestled back to its one inch plus of engagement, slid the strap clamp up so one bolt set was over the coupler and the rest over the exhaust pipe. And made it up.
Then I assemble the other 4 clamps for the support sleeves and that assembled about as hoped. With the addition of the tail pipe that was a souvenir of Omaha, the system was complete and I could finally put the coach back on the ground. (Of course I had forgotten to put air in the back and so could not get the last jack out until she came back near ride height.)
That's my story of a simple exhaust pipe replacement. I hope that this shortens someone's job.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Replacing the exhaust Pipe - final report [message #319591 is a reply to message #319558] |
Mon, 26 June 2017 09:27  |
GMC.LES
Messages: 505
Registered: April 2014
Karma: -2
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Senior Member |
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Matt
Would it have helped if you had loosened or disconnected the manifold ends of the front Y pipe to permit more movement?
Les Burt
Montreal
'75 Eleganza 26'
> On Jun 25, 2017, at 7:08 PM, Matt Colie wrote:
>
> Ken Henderson wrote on Sun, 25 June 2017 16:42
>> More likely it will convince many to HAVE it done! :)
>>
>> Ken H.
>>
>>> On Sun, Jun 25, 2017 at 3:44 PM, Matt Colie wrote:
>>>
>>> ...
>>>
>>> That's my story of a simple exhaust pipe replacement. I hope that this
>>> shortens someone's job.
>>> ...
>>>
>
> The Real Annoyance is that a couple weeks ago I was at Blain Merril's where there is a lift. But the honest fact is that if I lived in striking range
> of a good shop, I would a have farmed this one out.
>
> Matt
> --
> Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
> Electronically Controlled Quiet Engine Cooling Fan
> OE Rear Drum Brakes with Applied Control Arms
> SE Michigan - Twixt A2 and Detroit
>
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| Re: [GMCnet] Replacing the exhaust Pipe - final report [message #319598 is a reply to message #319591] |
Mon, 26 June 2017 10:09 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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Les Burt[1 wrote on Mon, 26 June 2017 10:27]Matt
Would it have helped if you had loosened or disconnected the manifold ends of the front Y pipe to permit more movement?
Les Burt
Montreal
'75 Eleganza 26'
Les,
It might have, But the fact is still that the Y-pipe is wrong and getting better engagement at the exhaust pipe joint would just have move the existing stress to someplace that has not yet been a problem. If I had a situation where I could get under there with an real torch, I am sure I could have made it better.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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