| Onan gaskets and RTV [message #133094] |
Sat, 02 July 2011 14:02  |
Wayne
Messages: 106
Registered: August 2004
Karma: 0
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Senior Member |
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Hi,
I am working on my Onan BF 4k. I went to my local Onan dealer for a pan gasket and found it is ONLY 22.50. But its not in stock so has to be ordered. Regular order is about 4 weeks but can be shipped next day for only $16. Must add CA confiscatory sales tax of only $2.50
It looks like it ONLY costs $40.00 to get a $3.00 gasket. The GOOD news it can be had.
Now the reason for this topic. The proper way to use RTV. I have never used RTV. I am going to use RTV every time I can for any gasket. Many folks say apply to 1 side and let it skin over for a few minuets and others say install right away. If you let it skin over then WHY? I have searched the internet but found conflicting answers. Besides I trust the answers I get here more.
Wayne Lawrence
76 Birchaven
Bellflower CA
w.lawrence@verizon.net
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| Re: Onan gaskets and RTV [message #133097 is a reply to message #133094] |
Sat, 02 July 2011 14:26  |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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Senior Member |
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| Wayne wrote on Sat, 02 July 2011 14:02 |
Hi,
I am working on my Onan BF 4k. I went to my local Onan dealer for a pan gasket and found it is ONLY 22.50. But its not in stock so has to be ordered. Regular order is about 4 weeks but can be shipped next day for only $16. Must add CA confiscatory sales tax of only $2.50
It looks like it ONLY costs $40.00 to get a $3.00 gasket. The GOOD news it can be had.
Now the reason for this topic. The proper way to use RTV. I have never used RTV. I am going to use RTV every time I can for any gasket. Many folks say apply to 1 side and let it skin over for a few minuets and others say install right away. If you let it skin over then WHY? I have searched the internet but found conflicting answers. Besides I trust the answers I get here more.
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Wayne,
I have made a number of gaskets for the Onan 4kw from sheet gasket material available at Autozone or such. I have not made an oil pan gasket -- how large is it?
Dennis
Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: Onan gaskets and RTV [message #133101 is a reply to message #133094] |
Sat, 02 July 2011 15:03 |
Wayne
Messages: 106
Registered: August 2004
Karma: 0
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Senior Member |
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Hi Dennis,
I would have to measure to be sure but about 10*10.
I have made gaskets out of a thin material. Just laid it over the hard part and tapped out a pattern on the edges. The pan was cork like material. I have never made one with cork.
Wayne Lawrence
76 Birchaven
Bellflower CA
w.lawrence@verizon.net
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| Re: [GMCnet] Onan gaskets and RTV [message #133102 is a reply to message #133101] |
Sat, 02 July 2011 15:16 |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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Senior Member |
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Wayne
That size sheet may be available at a larger parts store -- the
Autozone stock might be too small. The cork material cuts easily with
a razor knife. I used it for the covers over the valve adjusters.
Dennis
Dennis Sexton
73 GMC
Germantown, TN
Sent from my iPhone
On Jul 2, 2011, at 3:03 PM, Wayne Lawrence <wayne4@ca.rr.com> wrote:
>
>
> Hi Dennis,
>
> I would have to measure to be sure but about 10*10.
>
> I have made gaskets out of a thin material. Just laid it over the
> hard part and tapped out a pattern on the edges. The pan was cork
> like material. I have never made one with cork.
> --
> Wayne Lawrence
> 76 Birchaven
> Bellflower CA
> wayne4@ca.rr.com
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: [GMCnet] Onan gaskets and RTV [message #133109 is a reply to message #133094] |
Sat, 02 July 2011 17:04 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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If your familiar with the use of RTV, do it.
I thought GM was high, Onan is really high .
I'm an Onan dealer so I get 20% off, but high is high.
On Sat, Jul 2, 2011 at 12:02 PM, Wayne Lawrence <wayne4@ca.rr.com> wrote:
>
>
> Hi,
>
> I am working on my Onan BF 4k. I went to my local Onan dealer for a pan gasket and found it is ONLY 22.50. But its not in stock so has to be ordered. Regular order is about 4 weeks but can be shipped next day for only $16. Must add CA confiscatory sales tax of only $2.50
>
> It looks like it ONLY costs $40.00 to get a $3.00 gasket. The GOOD news it can be had.
>
> Now the reason for this topic. The proper way to use RTV. I have never used RTV. I am going to use RTV every time I can for any gasket. Many folks say apply to 1 side and let it skin over for a few minuets and others say install right away. If you let it skin over then WHY? I have searched the internet but found conflicting answers. Besides I trust the answers I get here more.
> --
> Wayne Lawrence
> 76 Birchaven
> Bellflower CA
> wayne4@ca.rr.com
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: Onan gaskets and RTV [message #133120 is a reply to message #133094] |
Sat, 02 July 2011 18:22 |
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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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| Wayne wrote on Sat, 02 July 2011 15:02 |
Hi,
I am working on my Onan BF 4k. I went to my local Onan dealer for a pan gasket and found it is ONLY 22.50. But its not in stock so has to be ordered. Regular order is about 4 weeks but can be shipped next day for only $16. Must add CA confiscatory sales tax of only $2.50
It looks like it ONLY costs $40.00 to get a $3.00 gasket. The GOOD news it can be had.
Now the reason for this topic. The proper way to use RTV. I have never used RTV. I am going to use RTV every time I can for any gasket. Many folks say apply to 1 side and let it skin over for a few minuets and others say install right away. If you let it skin over then WHY? I have searched the internet but found conflicting answers. Besides I trust the answers I get here more.
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Wayne,
I do not know what you found on the web, but I know what we found in my labs.
There are two reasons to let the RTV skin over prior to assembly and they are very different and both are important.
1 - The cured surface of the RTV assures that there will be some material thickness over the entire joint face. This is important because anyplace that the RTV is squeezed completely out of the joint there will be a leak path formed.
2 - The cured surface prevents the RTV from bonding to both surfaces. This is important because most joints move, either from operational loads, thermal movement, or vibration. RTV has very low tensile strength and any distortion of the cured material may cause it to tear - thus forming a leak path. (Ok, you thinking “its rubber - of course it can flex”. It can, but in those thicknesses, it can not flex far without breaking up.)
Just a short aside - always put the RTV on the part that is easiest to remove and clean.
Back to Wayne’s situation.
Did the pan gasket that you took out leak before you disassembled it?
Did the gasket come out intact?
If no and yes to the above, wipe it clean, keep it clean and put it back in exactly the way you found it. (Somewhere out there a votech teacher is crossing wrenches and shouting “Heresy!”.)
We were all taught that you should not reuse a gasket. It is my belief that this was a conspiracy started by the gasket companies. If it did not leak before and you did not break it, it will do as well the next time if you put it together properly. This only works if no parts of the joint are changed.
The most important thing with all thick rubber and bonded cork (all cork is bonded cork - cork and rubber mixed) is to resist crushing the gasket during assembly. Always resist the temptation to put more load in the joint (over torque the fasteners) because that is a sure way to crush and fracture the gasket material. The important thing is to get a good and even clamping load over the entire joint face. A distorted sheet metal cover will make this just about impossible. If you can see the part has been bent (like around the bolt holes), do your best to hammer it flat as you pretty much can’t make any worse.
You think you want to use RTV and a gasket?
Go ahead, this can make a really dry and very serviceable joint. Do it as a “Wet Assembly”. Put RTV on the part, then lay the gasket down over it and put it in place before the RTV cures. But - do not pull the fasteners to full load (don’t tighten things) Yet..... When everything is where it should be, take the fasteners up just snug (like use a socket and extension more like a screwdriver). A greasy hand is actually good here. Now, wait as long as you can before you pull the fasteners to nominal load (the middle of the torque spec).
Why did you do this???
Because the cured RTV: A - will bond the gasket to the part so the movement cannot break it and push it out of the joint and B - the RTV and gasket have now created a sealing element (you call a gasket) that is absolutely perfect custom fit to the joint thickness everywhere in the joint. When you tighten it up, you will put just the right compression (0.005~0.015) on the entire joint. And (side benefit), you will be able to open this joint and look inside any time you want and just put it back together with no hassle.
Matt (still try to sell some hard won lessons)
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: Onan gaskets and RTV [message #133143 is a reply to message #133094] |
Sat, 02 July 2011 21:11 |
Chr$
Messages: 2690
Registered: January 2004
Location: Scottsdale, AZ
Karma: 1
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Senior Member |
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I used high temp grey RTV on my valve covers on the 455 and they don't leak AT ALL. I'd be inclined to try it on the ONAN when the time comes.
sometimes gaskets just don't work well. i'm an RTV convert when it comes to engine work.
-Chr$: Perpetual SmartAss
Scottsdale, AZ
77 Ex-Kingsley 455 SOLD!
2010 Nomad 24 Ft TT 390W PV W/MPPT, EV4010 and custom cargo door.
Photosite: Chrisc GMC:"It has Begun" TT: "The Other Woman"
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| Re: Onan gaskets and RTV [message #133181 is a reply to message #133094] |
Sun, 03 July 2011 11:29 |
Wayne
Messages: 106
Registered: August 2004
Karma: 0
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Senior Member |
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Thanks to all who replied. Just the kind of info I was looking for.
Dennis, the cork material at Auto zone is big enough.
Matt & Robert, your explanation of how and why makes me more confident in the use of RTV.
Thanks to all of you.
Wayne Lawrence
76 Birchaven
Bellflower CA
w.lawrence@verizon.net
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