Home » Public Forums » GMCnet » leak at the black tank gate valve
| leak at the black tank gate valve [message #175111] |
Sat, 30 June 2012 06:37  |
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It appears that I have a leak (drip) in the general area of the black tank gate valve. I have not yet been under to survey the situation up close.
My question is how is the gate valve attached to the black tank? I'm assuming that if the gate valve is defective it is replaceable.
Bill Brown - '77 Buckeye Cruiser
Coshocton OH
carguybill@sbcglobal.net
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| Re: leak at the black tank gate valve [message #175114 is a reply to message #175111] |
Sat, 30 June 2012 07:38  |
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thanks guys. That helps. At least I now know what I'm looking at. Fearing the worst case, what's the chance that the white plastic adapter has broken loose from the tank itself?
Bill Brown - '77 Buckeye Cruiser
Coshocton OH
carguybill@sbcglobal.net
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| Re: leak at the black tank gate valve [message #175115 is a reply to message #175114] |
Sat, 30 June 2012 08:14 |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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Senior Member |
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| carguy wrote on Sat, 30 June 2012 07:38 |
thanks guys. That helps. At least I now know what I'm looking at. Fearing the worst case, what's the chance that the white plastic adapter has broken loose from the tank itself?
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Bill,
The white adapter has been known to crack. I would think the most likely issue is the gasket between the valve and the adapter.
It is likely that the screws holding the valve are rusted away and also that the threads in the white adapter have failed. For the bottom two screws you can drill and through bolt the valve.
All my experience has been on the 73 models with only one tank.
Dennis
Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: leak at the black tank gate valve [message #175138 is a reply to message #175111] |
Sat, 30 June 2012 12:18 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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On mine, the screws rusted and cracked the tank. 15 minutes and $25 at the plastic welding place fixed mine about 10 years ago. Use only stainless screws on reassembly. This all can be done with the tank still installed on the coach.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: leak at the black tank gate valve [message #176071 is a reply to message #175111] |
Sun, 08 July 2012 17:11 |
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Now that I've had a chance to look at the situation I now know that, as Matt suggested, the top threads are stripped. I should have no problem getting the hex head bolts out and redoing the upper threads would not be a problem if the tank was out but I really don't want to drop the tank.
It appears to me that there is little space to work between the tank flange and the cross member so now I'm asking for specific techniques used to restore the threads with the tank in place.
As always, thanks for your help.
Bill Brown - '77 Buckeye Cruiser
Coshocton OH
carguybill@sbcglobal.net
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| Re: leak at the black tank gate valve [message #176098 is a reply to message #176071] |
Sun, 08 July 2012 21:21 |
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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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| carguy wrote on Sun, 08 July 2012 18:11 |
Now that I've had a chance to look at the situation I now know that, as Matt suggested, the top threads are stripped. I should have no problem getting the hex head bolts out and redoing the upper threads would not be a problem if the tank was out but I really don't want to drop the tank.
It appears to me that there is little space to work between the tank flange and the cross member so now I'm asking for specific techniques used to restore the threads with the tank in place.
As always, thanks for your help.
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Bill,
When I did this to my tank six years ago, I did not have to drop the tank, but you do want it as clean as you can get it because you will have to take down the dump system. You will be under the coach and it will be dripping what ever is left in the tank.
You will be a great risk of collateral damage(imho) if you try to do this with the dump plumbing in place. It and the valve will have to be removed to give you room to work. With all that out of the way, you will have plenty of room to work. I don't recall that I had any particular difficulty at all with the operation other than that.
There were two different valves used in out coaches and I don't know when the change happened, but I am pretty sure it was before 77. The early coaches had the valve that was stainless on the tank side, I do not recall Thetford's number. The later had a valve that was plastic on both sides and somewhat thicker. That valve was Thetford's part 08709. The bolt holes in the all plastic valve could be drilled for a 5/16 fastener. I would not try it with the stainless front valve.
What I did, that has worked out very well was - with the tank in place - drill the top two holes for a 1/4-20 insert VERY CAREFULLY (the tank is very thin there). You might just try running the helicoil tap in, because if the existing thread has been stripped out, it is usually a good size for that. Then, tap it and run in the insert. There is a drive tag on the inset that needs to get broken off and removed. It is not that hard to cram your head so you can see into the hole and grab that broken off tag with a pair if long tweezers.
Helicoil is a trade name for a helical thread insert. This is a piece of diamond shaped wire wound as a thread. That wound wire has a drive tag that you use to turn the insert into the tapped hole. But, that tag must be broken off and removed before any fastener is inserted. This is not difficult and it is an included design feature.
You will probably need new fasteners for the top, they should be a length that protrudes through the valve body by 5/16~3/8 (the length of the insert and maybe a little more and not much more. If they bottom in the hole, you will have a very bad time of what comes after that.
Once you have the inserts in the top two holes, it would be smart to finger thread the replacement fasteners into the hole until they are gently bottomed and measure to be sure that the fastener is going to be against the valve when set in.
If this it the route you are taking, this would be the time to drill the bottom two holes for 1/4 bolts and through bolt them. You can do all this with stainless fasteners so you don't have to worry about it again. The nuts on the bottom two should be elastic stop nuts (nyloc) so no lock washers are needed. You won't need them on the upper pair, the inserts will do that. Washers everywhere will help with the way plastic creeps.
If you can't get a hold of 1/4-20 helicoil inserts and tools, contact me and I can lend you my set.
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: leak at the black tank gate valve [message #176103 is a reply to message #176071] |
Sun, 08 July 2012 21:43 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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Senior Member |
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| carguy wrote on Sun, 08 July 2012 15:11 |
Now that I've had a chance to look at the situation I now know that, as Matt suggested, the top threads are stripped. I should have no problem getting the hex head bolts out and redoing the upper threads would not be a problem if the tank was out but I really don't want to drop the tank.
It appears to me that there is little space to work between the tank flange and the cross member so now I'm asking for specific techniques used to restore the threads with the tank in place.
As always, thanks for your help.
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I'm reluctant to even suggest this, but in this case it might just work: In my early life of working on cars, I would occasionally run across a stripped thread and I discovered that there were metric size bolts that were just slightly larger than the SAE fasteners and they had similar thread pitches. I have taken an appropriate sized metric bolt, ground or filed a notch in the side of the first few threads (picture a self tapping bolt) and carefully turned it in, while cutting new threads.
Obviously this is NOT the right way to do this. The RIGHT way is to do what Matt suggests and install a Helicoil thread insert. But, the metric bolt trick might work well enough in this application, especially if you use some sort of thread sealant or locker.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| Re: leak at the black tank gate valve [message #176107 is a reply to message #175111] |
Sun, 08 July 2012 22:31 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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I too have the Drip Drip Drip just forward of the the gate valve. I painted the previously repaired area with Through The Roof and I was sure that would fix it but nope, as it wasn't perfectly dry at app time. AND my gate valve is leaking. SO I think it's time to call Jim K for a new tank, valve and macerator and be done with this S#$%* job for once and for all as the plastic is beyond it's service life. I need to look up and brush up on how this meets the floor drain and the toilet connection though before attempting. IF anyone can quickly point me at that disertation it would help.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: leak at the black tank gate valve [message #176125 is a reply to message #176103] |
Mon, 09 July 2012 07:38 |
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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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| Carl S. wrote on Sun, 08 July 2012 22:43 |
I'm reluctant to even suggest this, but in this case it might just work: In my early life of working on cars, I would occasionally run across a stripped thread and I discovered that there were metric size bolts that were just slightly larger than the SAE fasteners and they had similar thread pitches. I have taken an appropriate sized metric bolt, ground or filed a notch in the side of the first few threads (picture a self tapping bolt) and carefully turned it in, while cutting new threads.
Obviously this is NOT the right way to do this. The RIGHT way is to do what Matt suggests and install a Helicoil thread insert. But, the metric bolt trick might work well enough in this application, especially if you use some sort of thread sealant or locker.
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Carl,
That is really a cheap and sleazy fix that has also worked for me on a couple of occasions.
What I wanted to add before this got very far was that with the threads being in polypropylene (or polyethylene), the chance that the thread locker will do any good at all is almost non-existent. It may manage some small level of mechanical interference, but even that won't stand any challenge. (Want to see the T-shirt?)
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: leak at the black tank gate valve [message #176132 is a reply to message #176125] |
Mon, 09 July 2012 10:21 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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Senior Member |
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| Matt Colie wrote on Mon, 09 July 2012 05:38 |
| Carl S. wrote on Sun, 08 July 2012 22:43 |
I'm reluctant to even suggest this, but in this case it might just work: In my early life of working on cars, I would occasionally run across a stripped thread and I discovered that there were metric size bolts that were just slightly larger than the SAE fasteners and they had similar thread pitches. I have taken an appropriate sized metric bolt, ground or filed a notch in the side of the first few threads (picture a self tapping bolt) and carefully turned it in, while cutting new threads.
Obviously this is NOT the right way to do this. The RIGHT way is to do what Matt suggests and install a Helicoil thread insert. But, the metric bolt trick might work well enough in this application, especially if you use some sort of thread sealant or locker.
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Carl,
That is really a cheap and sleazy fix that has also worked for me on a couple of occasions.
What I wanted to add before this got very far was that with the threads being in polypropylene (or polyethylene), the chance that the thread locker will do any good at all is almost non-existent. It may manage some small level of mechanical interference, but even that won't stand any challenge. (Want to see the T-shirt?)
Matt
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Matt,
I'm glad to hear that someone else here has done that 'sleazy' fix too. I try not to make a habit of doing stuff like that, but sometimes it is just necessary when you don't have the time or resources to fix it right, and when it really doesn't matter that much.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| Re: leak at the black tank gate valve [message #176135 is a reply to message #176132] |
Mon, 09 July 2012 12:00 |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
Karma: 1
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Senior Member |
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| Carl S. wrote on Mon, 09 July 2012 10:21 |
Matt,
I'm glad to hear that someone else here has done that 'sleazy' fix too. I try not to make a habit of doing stuff like that, but sometimes it is just necessary when you don't have the time or resources to fix it right, and when it really doesn't matter that much.
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I guess when you say "when it really doesn't matter that much" that I don't need to find grade 8 bolts for this application. <GRIN>
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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| Re: leak at the black tank gate valve [message #176142 is a reply to message #176135] |
Mon, 09 July 2012 13:39 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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Senior Member |
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| midlf wrote on Mon, 09 July 2012 10:00 |
I guess when you say "when it really doesn't matter that much" that I don't need to find grade 8 bolts for this application. <GRIN>
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Right, no grade 8's required.  I would, however, go with stainless steel and a course thread (picture plastic screws).
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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