Subborn Hydraulic Leak

[AceDeuce]

Can anyone recommend something better than teflon tape to seal threads on hydraulic fittings? I can't seem to get the hydraulic block that supplies pressure to the FEL valve to stop leaking.

 

[Sherweld]

Lots of discussion happening on other threads at the moment regarding proper thread sealing.
The most important thing to know right off, is exactly what type of threaded fitting is being discussed. Virtually the only thread type where tape or dope is recommended is a tapered pipe thread (IPS) All other fitting types seal by other means.

 

[AceDeuce]

As far as I can tell, the culprit is a 1/4 NPT fitting. All efforts to use teflon tape have resulted in a small, weeping leak.

 

[B2400]

I use "Oatey's" teflon paste for all my threaded fittings. Put a little on finger, spread around thread and tighten down.

 

[Sherweld]

Okay, Is it possible that the fitting may have been over-tightened at some point? This possibly could cause distortion or even a hairline crack to develop, either of which may be almost impossible to detect by just eyeballing. Here's a link that may be helpful in the future Better Farming - Power at Work - 2006

Sorry, I don't have any product to recommend because I've been lucky enough to have not had the problem.

 

[tommu56]

Is there any chance it is an o ring seal? and the o ring is bad.

tommu

PS on here a picture is worth 10,000 words at least.

 

[AceDeuce]

The idea of a hairline crack came to me after about the 5th or 6th time reassmembling the block. So I bought a new block -- same result. I've replaced the fittings and o-rings with new ones twice -- same result. BTW, I did suspect a bad o-ring or possibly a counterbore that was too deep on the block which also factored into the decision to replace the block, but neither turned out to be the case. I triple checked by cleaning the entire surrounding area to verify where the leak was coming from. The o-rings appear to be sealing properly. I normally use the "right" amount of torque on the fittings (hand tighten, then one more complete rotation + enough to make the fitting face the right direction). And I've tried the "wrong" way... really cranking down the fitting until it felt like it was ready to twist off -- again, same result. Hence my frustration.

So I started thinking maybe operator error? As far as I know I'm doing this correctly. Anyone feel free to chime in and tell me what I might be doing wrong -- at this point I have no pride left. But, I'm not going to let an inanimate object kick my butt!

 

[Sherweld]

Now you have me puzzled?

"O" rings on a NPT fitting are new to me. NPT threads are cut on a taper, so the threads get mashed together the more it is tightened which is supposed to provide the seal. An "O" ring normally wouldn't/couldn't have any function with NPT.

Is it possible to give us a photo of the offending part?

 

[AceDeuce]

O-rings are on the back of the block at the interface to the pump. The NPT fittings (separate) are in the side and bottom of the block and go to the control valve. Sorry, I realized I might have made a confusing statement. I'll try to get pictures up tomorrow -- am supposed to be working right now

 

[Jason537]

On a couple occasions, I have had to change out the small block to get it to stop leaking,.. another time I had to change the fitting because it was cracked but VERY hard to see.

I also only use liquid teflon,. or pipe dope when installing loaders or doing hydraulic work,.. tighten up them fittings tight as well.

 

[ozzie tractor]

ok im going to take a stab in the dark here. you are trying to seal the hydraulic block which is used to take oil off the transmission for the front end loader. its a square block with 2 fittings which screw into it and it has 2 o rings behind it to seal against the trans.

how did i go, was i close. if this is the issue cut a bit off the fittings because they bottom out before they are tight enough in the thread to seal. o and i use loctite pipe sealer, the white stuff.

 

[AceDeuce]

Sorry, no pics yet. Too dark to go out and take pictures in the barn last night by the time I got home.

So far I haven't tried anything other than regular teflon tape as a sealing agent. It sounds like it might be worth trying pipe dope or something else.

Heck, it goes against my signature line but I think if the above doesn't work I'll break out the brazing torch!

 

[Sherweld]

ok im going to take a stab in the dark here. you are trying to seal the hydraulic block which is used to take oil off the transmission for the front end loader. its a square block with 2 fittings which screw into it and it has 2 o rings behind it to seal against the trans.

how did i go, was i close. if this is the issue cut a bit off the fittings because they bottom out before they are tight enough in the thread to seal. o and i use loctite pipe sealer, the white stuff.

Getting the picture now. Ozzie may well be on to something. If the replacement block was made to the same specs as the original and the standard male fitting was indeed "bottoming out" before full thread engagement, you have nothing to lose by taking either block and either fitting (original or replacement) and taking a couple of threads at the most off the fitting and try it out (after cleaning any chips of course )