air leaks and onan exhaust

K

kab7

Active member
Sep 14, 2009
1,230
2
38
San Jose, CA
We've got a propane/CO detector mounted low on the face of the bath module (this is a 75 Eleganza floorplan, more or less).
When running the Onan recently, it kept setting off the detector, meaning somehow the Onan exhaust is getting into the coach.
All the windows and vents were closed at the time. Running the roof fans, in or out, didn't help.

I've long suspected air leaks from somewhere under the coach, but haven't been able to figure out where they are.
Anybody got a clue on this? I've looked under the bath module (from inside the coach), but don't see anything obvious.

thanks,
Karen
1975 26'
 
Seams between the body and genet compartment opening as the body spreads from age.
Tom, MS II
--
1975 GMC Avion
KA4CSG
 
> Seams between the body and genet compartment opening as the body spreads from age.
> Tom, MS II

I opened up both the genset and propane compartment doors to check, and there's a good foam seal at the edges where the compartments meet the body
panels.
This is a 75, so the compartments are welded aluminum. I'd previously found that the slots they cut into the aluminum channels for the latches was
an
air leak, so sealed them with expanding foam. I also foamed any small gaps I could see around the edges. There must be some other gaps somewhere,
but I haven't found them yet. I guess I'll experiment with setting all the fans to blow in or out and see if I can detect air movement from outside.

thanks,
Karen
 
> Is this happening while driving down the road or while it is parked?
>
> I would be looking closely at the exhaust system for leaks including gaskets clamps and condition of the muffler and pipes.
>
> Some people have resorted to things like this for parked generator operation:
>
> http://www.doityourselfrv.com/how-to-make-homemade-rv-gen-turi/#
>
> https://www.amazon.com/Camco-44461-Gen-Turi-Generator-Exhaust/dp/B000BUU5XG

Thanks Ken, I'm probably going to build one of those. I'll also look more closely at the genset itself.
It was while the coach was parked. It was a breezy night, so the exhaust was likely being blown under the coach.

Someone wrote to me privately and suggested the hole for the black tank pipe to the toilet as a likely air leak.
I'd thought about dropping the black tank to look, but turns out it wouldn't have helped because the pipe is
attached to the black tank, and the OEM seal (a thick piece of plastic) is screwed to the top of the plywood under
the bath module. If you drop the tank, you won't see how the pipe sits in the hole.
On ours, they didn't align the tank to the hole very well, leaving a sizable gap that mice made even bigger:
http://www.gmcmhphotos.com/photos/original-details/p62457-hole-in-the-floor-for-toilet.html

For anyone considering this, you have to pull the toilet and remove the screws holding the plastic toilet flange
to the bottom of the shower. The flange itself screws onto the 3" riser pipe out of the black tank. Unscrew that,
and you can look down at the alleged seal. You might be able to see it by taking off the toe kick under the bath module,
but on ours the shower drain pipe mostly obstructs the view. I used a USB camera there first and found the gaping hole.
Getting at it is another matter.

There are probably other air leaks as well, but this is a pretty big one.

thanks,
Karen
1975 26'
 
Don't forget the gaps between the cockpit floor and the sides that happens as the coaches age. I had a tremendous influx of engine fumes coming in
there while underway. Onan runs a little rich and when the wind came from the rear the fumes would eventually come in through those gaps. Onan still
wafts in the door after closing those gaps so I got a super flexible crush proof exhaust hose from Amazon to carry his fumes 12 feet away when parked.
Expensive, but useful when working on other running engines also. I'll still use it until I get a power source with no exhaust.
--
Terry Kelpien

ASE Master Technician

73 Glacier 260

Smithfield, Va.
 
> We've got a propane/CO detector mounted low on the face of the bath module (this is a 75 Eleganza floorplan, more or less).
> When running the Onan recently, it kept setting off the detector, meaning somehow the Onan exhaust is getting into the coach.
> All the windows and vents were closed at the time. Running the roof fans, in or out, didn't help.
>
> I've long suspected air leaks from somewhere under the coach, but haven't been able to figure out where they are.
> Anybody got a clue on this? I've looked under the bath module (from inside the coach), but don't see anything obvious.
>
> thanks,
> Karen
> 1975 26'

The sink drain connection to the black tank is another path for this to happen. Ours had some of the rubber like seal missing so I removed it and
used a cut up license plate as a barrier. Think you have a 26-3 floorplan and if so it looks like this under the cabinet opposite the bath.
http://www.gmcmhphotos.com/photos/power-level-valve-fitting/p62458-sink-drain-connection-to-tank.html
http://www.gmcmhphotos.com/photos/power-level-valve-fitting/p62459-sink-drain-connection-to-tank.html
--
Wally Anderson
Omaha NE
75 Glenbrook
Megasquirt III injection
Bob Stone hydroBOOOOST
Manny reaction arm system
Branscombe Kelsey Hayes park brake
http://wallyandsue.blogspot.com/
 
> Don't forget the gaps between the cockpit floor and the sides that happens as the coaches age. I had a tremendous influx of engine fumes coming in
> there while underway and Onan fumes when parked. Onan runs a little rich and when the wind came from the rear the fumes would eventually come in
> through those gaps. Onan still wafts in the door after closing those gaps so I got a super flexible crush proof exhaust hose from Amazon to carry
> his fumes 12 feet away when parked. Expensive, but useful when working on other running engines also. I'll still use it until I get a power source
> with no exhaust.

Good thought. Is it possible to see the gaps from under the coach (with the wheel liners removed)? Or do you have
to pull the cockpit side panels to get at them? I know the 73 we used to have had an enormous
hole cut in the plywood where the gasoline fill tube runs through the floor. I patched it closed when I repaired
the water damage. I'll have to look at what the 75 is like there.

I also noticed a breeze coming in through the cockpit AC ducts when I had all the roof vents set to blow out.
Haven't gotten a chance to investigate that yet.

Karen
1975 26'
 
On mine, I could see the gaps from above by removing the bins in the side panels and having a light on underneath the floor even with the wheel well
liners in place. There are several people that have used different methods of repair, and I went my own route with minimal expanding foam and
fiberglass/resin repair to the plywood floor. I still had to remove the side panels to do the job...and that was a bit of a PITA because I was scared
they would crack somewhere I could not repair.
--
Terry Kelpien

ASE Master Technician

73 Glacier 260

Smithfield, Va.
 
Here is another thought that you might try if you think the exhaust is coming in from the bottom of the coach. Ragusa, and others, make an Onan
cooling air deflector. I realize that it is not for the exhaust itself but the Onan draws cooling air in from the bottom and rear. The cooling air
is blown into the engine area and back on to the ground again. If exhaust gasses get mixed in there it would also get recirculated around and around
again. Installing one of these deflectors would take the cooling air and any accumulated exhaust gas and blow it away from the coach. That would
provide more fresh cooling air in the area around Onan. I have one of these on my Onan.

http://www.appliedgmc.com/prod.itml/icOid/631

http://www.ragusarv.com/ Look for RV-117 or RV-122

Here is another one from Jim at Applied GMC and 1/2 of the cost of the Ragusa one.

http://www.appliedgmc.com/prod.itml/icOid/891

--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
> Here is another thought that you might try if you think the exhaust is coming in from the bottom of the coach. Ragusa, and others, make an Onan
> cooling air deflector. I realize that it is not for the exhaust itself but the Onan draws cooling air in from the bottom and rear. The cooling air
> is blown into the engine area and back on to the ground again. If exhaust gasses get mixed in there it would also get recirculated around and
> around again. Installing one of these deflectors would take the cooling air and any accumulated exhaust gas and blow it away from the coach. That
> would provide more fresh cooling air in the area around Onan. I have one of these on my Onan.

Are there any pictures of how/where these are installed? I searched but couldn't find anything.

thanks,
Karen
1975 26'
 
Karen,
My CO detector goes off sometimes with Onan running.
I think the weather stripping on the window above the Onan is leaking.

Regards,
Bill
--
Bill Wevers GMC49ers, GMC Western States
1975 Glenbrook - Manny Powerdrive, OneTon
455 F Block, G heads
San Jose
 
Ken,

I have one of each and I can assure you that Darren's
unit is definitely the winner.

Gary Kosier
77PB w/500Cad
Newark, Ohio

--------------------------------------------------
From: "Ken Burton"
Sent: Thursday, March 16, 2017 9:30 PM
To:
Subject: Re: [GMCnet] air leaks and onan exhaust

> Here is Darren Paget's version installed on someone's coach.
>
> http://www.palmbeachgmc.com/gmc/gmc_images/deflector5.jpg
>
> I'm still looking for a picture of a Ragusa one.
>
>
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
> Ken,
>
> I have one of each and I can assure you that Darren's
> unit is definitely the winner.
>
> Gary Kosier
> 77PB w/500Cad
> Newark, Ohio

I have the Ragusa one. I have never seen one of Darren's installed on a coach. I also do not run around rallys looking at Onan air exhausts. I
think Darren's is no longer available but you sure could copy it and make one yourself.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
Ken,

Darren's unit is a SS tray with ball bearing slides on the sides.
It will come all the way out and he claimed it support 300 lbs.
when out. It also has a good latch to keep it in.

Gary Kosier
77PB w/500Cad
Newark, Ohio

--------------------------------------------------
From: "Ken Burton"
Sent: Friday, March 17, 2017 8:48 AM
To:
Subject: Re: [GMCnet] air leaks and onan exhaust

>> Ken,
>>
>> I have one of each and I can assure you that Darren's
>> unit is definitely the winner.
>>
>> Gary Kosier
>> 77PB w/500Cad
>> Newark, Ohio
>
> I have the Ragusa one. I have never seen one of Darren's installed on a
> coach. I also do not run around rallys looking at Onan air exhausts. I
> think Darren's is no longer available but you sure could copy it and make
> one yourself.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
Yes, that is Daarren’s battery tray and I have one of those.
However what people are referring to is the metal curved plate that mounts under the air exhaust beneath the flywheel of the Onan. This plate deflects the exhaust air so that it blows away from the side of the motorhome rather than into the dirt beneath it.
I also have the one made by Darren Paget.

Does anyone know what Darren is doing these days? The last I knew a few years ago what that he was a hunting guide in Canada.
Jim Bounds probably knows as he and Darren got together frequently in the past at Orlando.

I think that the last time I saw Darren was at the GMCMI convention held at Mt. Hood back in Fall 2000.

Emery Stora
77 Kingsley
Frederick, CO

>
> Ken,
>
> Darren's unit is a SS tray with ball bearing slides on the sides.
> It will come all the way out and he claimed it support 300 lbs.
> when out. It also has a good latch to keep it in.
>
> Gary Kosier
> 77PB w/500Cad
> Newark, Ohio
>
> --------------------------------------------------
> From: "Ken Burton"
> Sent: Friday, March 17, 2017 8:48 AM
> To:
> Subject: Re: [GMCnet] air leaks and onan exhaust
>

>>> Ken,
>>>
>>> I have one of each and I can assure you that Darren's
>>> unit is definitely the winner.
>>>
>>> Gary Kosier
>>> 77PB w/500Cad
>>> Newark, Ohio
>>
>> I have the Ragusa one. I have never seen one of Darren's installed on a coach. I also do not run around rallys looking at Onan air exhausts. I
>> think Darren's is no longer available but you sure could copy it and make one yourself.
>> --
>> Ken Burton - N9KB
>> 76 Palm Beach
>> Hebron, Indiana
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
The last I knew of him he was still with the Calgary Fire Department.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
well, so far so good. Ran the Onan for about an hour today and the CO alarm didn't even blink funny.
Sealing up that huge gap around the toilet tube might have fixed it. The exhaust was going
under the coach and coming out the other side, so likely a good test case. We even ran the bathroom
vent blowing out for a while, and it didn't suck anything in to set off the detector. It did, however,
pull a little exhaust stink in around the roof AC, which surprised me.

I'm still going to build an air deflector and a genturi though. Man that thing stinks.

thanks,
Karen
1975 26'
 
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