Hydraulic Leak

[woodbutcher]

The hose that supplies the lift cylinder on my front-loader leaks at the connection. The fitting that attaches to the cylinder has male boss threads and an o-ring on one side, and swivel female pipe threads that connect to the half inch hose. I've replaced the fitting three times and the hose twice, but it still leaks. I use teflon tape for a sealer. It did the job on all the other hoses I replaced. Any ideas?
Butch

 

[Daniel Ky]

Make sure you wrap the teflon tape in a clockwise direction so it does not unwind itself when you tighten the fitting.

 

[esd19]

Where is it leaking from. If its leaking from the swivel maybe its a defective fitting.

 

[Anonymous-0]

The o-ring fitting seals with the o-ring, not the threads. You may need to replace the o-ring. The last step in assembling an o-ring fitting is to tighten the nut behind the o-ring against the female thread.

Most hydraulic vendors don't like teflon tape because it can break off pieces that are bigger than passages in valves and pumps and then causes them to not work well.


Gerald J.

 

[Jerry/MT]

All the hydraulic experts I know say not to use teflon tape. It shreds and pieces can get into the control ports on the valves I use a Loctite sealer specially made for hydraulic lines. It costs a few dollars and works like a champ.

 

[NC Wayne]

If the fitting going into the cylinder is an O-ring boss fitting then it needs no sealer because the o-ring does the job of sealing. If that's where it's leaking look carefully at the beveled area where the o-ring seats and make sure it's clean and not rusted, no burrs, etc. Too these fittings have their own special o-rings that are just a bit different sized than a "standard" one. If the o-ring in it isn't the right one for those fittings it can cause it to leak. Now the other end your describing with the swivel going to a pipe fitting is supposed to be a metal to metal seal. It seals between the beveled end of the pipe fitting on the hose and the conical shaped seat inside the swivel. If your using teflon tape on the threads it might be causing the nut to get tight before the fittings actually seat together. You'd be amazed how many fittings I see that have the threads wrapped in tape where it's doing nothing at all for the actual sealing surfaces. Also check the end of the fitting on the hose as well as the seat in the swivel end and make sure both parts look good and aren't nicked, scarred, rusted, etc. Anything kind of defect in a metal to metal sealing area like this can cause it to leak. Good luck.

 

[KIDbob]

Like the others said do not use tefflon tape on hydraulic fittings. In this case do not use any sealer because the threads do not do the sealing. As NC Wayne said the boss fitting uses a special fitting oring.
Also look at the seat in the swivel fitting, if the seat is convex it is for a male pipe hose end, if it is concave it is for a JIC 37deg. male hose end. If it is for JIC the thread will be loose fitting and will not seat on pipe.

 

[woodbutcher]

Thanks to all. The leak seems to be coming from the swivel connection, so the teflon tape may have allowed the nut to tighten before the seal surfaces made contact.
Butch

 

[souNdguy]

Correct.

Swivel on the pipe fitting means it doesn't seal by thread deformation like pipe threads -normaly- do.

Soundguy