Sheridan Sheridan Pre-C Series Repair Advice Requested

[pwcosol]

Gents:

Joined the AGN Forum a few days back. Everyone has been both friendly and helpful. Had mentioned the airgun in my post header and was directed here. Based on the majority of airguns I own, sounds like the right place! Though I have done minor repairs on some Sheridan C-series rifles, have yet to change out a valve seal. I do have a few complete seal replacement kits with valve tool included on hand. Also posted a few pics of the rifle in question. The handguard/pump assembly had already been removed by me. Pump seal was hard, cracked and removed. It was then I noticed, in comparison to the C-Series rifles, it is not a welded affair. Both stirrup and cup with seal were threaded/bolted to the connecting rod. In addition, pump seal was formed into the cup when made and retained by nasty little bent pieces of steel. This also makes it impossible to use a current pump seal, as there is no inside "lip" for seal groove to engage with.

Utilizing another forend with good seal, found pressure resistance when pumping. However, after stopping at the 4th pump to check, heard hissing air coming out the barrel at muzzle for a couple seconds then nothing. I suspect a issue with either a lead seal or maybe valve itself. So, ordered a valve repair kit today. Prior to joining the AGN Forum I stumbled upon a BLOG site regarding repair for this AR and a host of other air arms. I really wanted to thank the author but found no way to contact him. Thought I would provide URLs to all four installments of the author's article, as I found it very helpful to understanding just what I will be dealing with:

https://anotherairgunblog.blogspot.com/2014/07/early-sheridan-model-c-part-1.html

https://anotherairgunblog.blogspot.com/2014/07/early-sheridan-model-c-part-2.html

https://anotherairgunblog.blogspot.com/2014/07/early-sheridan-model-c-part-3.html

https://anotherairgunblog.blogspot.com/2014/07/early-sheridan-model-c-part-4.html

Lastly, wanted to post a few photos of my rifle as well for reference. Would appreciate hearing from the membership regarding things to be aware of in replacing the valve assembly, checking the OEM parts, and particularly when securing the valve assembly with lock nut. Seems there should be a specific torque specification for how tight it needbe when locking it down...Thanks!

 

[Wadcutter]

The rubber cups in the early pump heads can be replaced. You just have to dig the old rubber out of the head and then cut those teeth out. A lathe comes in handy, but can also be removed by other methods. The new seal will then slip into the head, but will have to be held in place using some sort of epoxy or rubber cement.
Early pump head on left

 

[6gun]

There's one cheater move for dried pump seals that I have used along with simple green (not together) . It is not ideal because it softens the rubber but it works and has kept at least 1 pump going for a long time for me. Automotive "snake oil" at 205 reseal. It swells your seals.

AT-205 has one ingredient, diethylene glycol monoethyl ether, CAS 111-90-0, A.K.A. "carbitol". It is a solvent,

 

[DonR]

A few things to attend to once you've taken it apart:
- Clean the internals scrupulously, removing all dried oily gunk and remnants of old seals.
- Polish the metal surfaces that mate with the inlet and exhaust valves - slight irregularities can cause leakage.
- When installing the valve body, your older gun will likely have a tiny tab that orients that part correctly to align the transfer port - make sure it's lined up properly as you install it.
- As to valve nut torque, in my opinion 'more is better' but this is using only about an 8" bar on the install tool - you want to squish the valve gasket stoutly.

Don R.

 

[pwcosol]

WC:
Thanks for the tips on replacing the pump seal in the original pump cup. Just so happens I have a Logan 9B bench lathe, ENCO bench mill (and honorable mention to a Sherline table-top lathe as well). In looking a the OEM seal cup, had pushed the steel tabs downwards in the hope when I stuffed seal in, the tabs would help prevent it from coming backing out. It seemed to help somewhat, but seal needed support from the groove. Test pumps showed the seal pulling away a bit on return pumping. Was also considering applying BARGE contact cement in the cup as well, but held off. A thought occurred to me that possibly I could turn down the material at the very end of the cup equating to the thickness of steel rim found on later C-series seal cups. Then insert a turned down steel washer, etc. of proper OD and thickness by pressing it in and subsequent soldering. Lastly, could turn down the ID to the right width and there is my rim to mate with the one on the seal. If all else fails, could still use a later pump rod assembly and just keep the original one with the rifle...

 

[pwcosol]

Thanks to 6gun & DonR for your thoughts as well. Regarding the seals, took to measuring the width of them at outwards edge. New seal OD comes in at around .790 or perhaps .002-3 inch wider. Used seals will vary, but get down to around .760 or less and seal is done for. Seal becoming hard is even worse. One used, clean seal still maintaining a decent degree of elasticity came in at .770. In a test it performed perfectly when installed in the Sheridan from my OP. Got a opposite reaction when trying this with another pump rod having a new seal. Pump tube is close to new inside and there was no residue of any kind in it.

To DonR:
You know the valve assembly well. Perhaps you could enlighten me just how the valve system works from time you are compressing a full pump of air into the air chamber. There must be some sort of one-way check valve which lets air in but not out (until the valve opens directing air from chamber into receiver duct which empties into the chamber sealed to rear by locked bolt face and pellet on forward end). Also cleaning of valve components. My expectation is the original ones will be close to new. Would appreciate it if you can clarify each of the pictured components and ones (and where) I should pay special attention to:

 

[DonR]

Well, left to right in your photo from airgunblogspot #3: inlet (check) valve; inlet spring; separating washer; exhaust valve spring; exhaust valve; then valve body; outer lead seal (which some folks don't bother replacing) and retaining nut. Not shown in that pic' but covered just later in blogspot #3 is the seal in front of the valve body which may be a lead ring as shown in his pic' below. Your new seal kit may use a plastic/elastomer seal here.
Inlet and exhaust valves plus seal rings get replaced; clean other parts by your favorite solvent, rags, brass brush, etc. including for sure threads on the retaining nut.
As noted in the blogspot, most service kits have an exhaust valve nose that needs turning down to fit into the spring.
** You may already know you'll also need the 'special tool' with square drive on one end and 9/32-32 female for valve extraction on the other.
WC's method for the pump cup looks good to me - he's worked on plenty of these. Too much effort to replicate the later cup style with rim.